Engineering plastics 1847355692, 9781847355690, 1847355684, 9781847355683

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Engineering Plastics

T.R. Crompton

Top left front cover image: Lockheed Martin’s F-35 Lightning II beneits from a range of high-temperature thermoset composites in its construction. ©Lockheed Martin Corporation

Engineering Plastics

T.R. Crompton

A Smithers Group Company Shawbury, Shrewsbury, Shropshire, SY4 4NR, United Kingdom Telephone: +44 (0)1939 250383 Fax: +44 (0)1939 251118 http://www.polymer-books.com

First Published in 2014 by

Smithers Rapra Technology Ltd Shawbury, Shrewsbury, Shropshire, SY4 4NR, UK

©Smithers Information Ltd., 2014

All rights reserved. Except as permitted under current legislation no part of this publication may be photocopied, reproduced or distributed in any form or by any means or stored in a database or retrieval system, without the prior permission from the copyright holder.

A catalogue record for this book is available from the British Library.

Every effort has been made to contact copyright holders of any material reproduced within the text and the author and publishers apologise if any have been overlooked.

ISBN: 978-1-84735-568-3 (hardback) 978-1-84735-569-0 (softback) 978-1-84735-570-6 (ebook)

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P

reface

This book aims to provide a complete review of the use of polymers in engineering but irst it is necessary to discuss what is meant by an engineering plastic. Generally speaking, engineering plastics are those, which are replacing conventional materials such as metals and alloys in general engineering. In addition, the term engineering plastic covers materials that have superior properties, which were not particularly available in conventional polymeric materials such as the exceptionally high heat resistance of polyimides and polysulides. Engineering polymers can be reinforced by including in their formulations, glass ibres, carbon ibres and nanotubes, which produce appreciable improvements in mechanical and thermal properties. In addition to conventional materials engineering polymers include materials as diverse as polyether ether ketone, polyimide, polyetherimide and polysulides. The book aims to provide a complete coverage of the types of plastics, which are now increasingly being used in engineering in applications as diverse as gears, aircraft body construction, micro-electronics and extreme high temperature applications, steel replacement and artiicial hip joints. Chapters 1-4 of the book deal with the mechanical, electrical and thermal properties of a wide range of unreinforced and reinforced engineering plastics. Chapter 5 discusses various miscellaneous properties such as wear, abrasion resistance, frictional hardness properties, surface properties and weathering, and chemical resistance. In addition, this chapter covers a particular property of food packaging plastics, namely their gas barrier properties. Chapter 5 concludes with a discussion of the prediction of the service lifetime to be expected of engineering plastics. Chapters 6-8 discuss the application of plastics in various types of industry including automotive, aerospace, mechanical and general engineering.

iii

Engineering Plastics Plastics are now being used as a replacement in applications as diverse as gears, aircraft body’s constructions, micro-electronics, extreme high-temperature applications and hip joints. The mechanical, electrical and thermal properties of polymers will be discussed. Other diverse applications such as solvent and detergent resistance, frictional hardness properties, food packaging applications and gas barrier properties are also discussed. In addition a very important application is discussed, the resistance of plastics to gamma and other forms of radiation in the nuclear industry, medical applications and food sterilisation. The book will be of interest to those at all levels who are concerned with general engineering, and the building, automotive, aerospace, electronics, mechanical and nuclear industries. It will also be of interest as a source book to materials scientists, to those concerned with the development of new materials and students of engineering and related studies.

iv

C

ontents

1

2

Introduction ............................................................................................... 1 1.1

Mechanical Applications ................................................................. 2

1.2

Electrical Applications .................................................................... 3

1.3

Thermal Applications ..................................................................... 3

1.4

Miscellaneous Applications ............................................................. 3

1.5

Signiicant Polymer Properties ......................................................... 3

Mechanical Properties of Polymers............................................................. 7 2.1

Review of Mechanical Properties .................................................... 7

2.2

Mechanical Properties of Unreinforced Polymers .......................... 14 2.2.1

Polyoleins ....................................................................... 14

2.2.2

Polyphenylene Oxide ....................................................... 16

2.2.3

Epoxy Resin ..................................................................... 16

2.2.4

Acrylic Resins .................................................................. 16

2.2.5

Polyether Ether Ketone .................................................... 17

2.2.6

Polyethylene Terephthalate .............................................. 17

2.2.7

Polyimides ....................................................................... 18

2.2.8

Fluorinated Polyimides .................................................... 18

2.2.9

Polyamide-imide .............................................................. 19

2.2.10 Polyamides ....................................................................... 19 2.2.11 Polyurethanes .................................................................. 23 2.2.12 Polyphenyl Sulfone .......................................................... 24 2.3

Reinforced Plastics ........................................................................ 24 2.3.1

Glass Fibre Reinforcement ............................................... 24

v

Engineering Plastics

2.4

2.5

2.3.2

Applications of Carbon Fibre Reinforcement ................... 24

2.3.3

Other Reinforcing Agents ................................................ 24

Comparison of the Mechanical Properties of Virgin and Reinforced Plastics ........................................................................ 28 2.4.1

Tensile Strength................................................................ 28

2.4.2

Flexural Modulus ............................................................ 29

2.4.3

Elongation at Break ......................................................... 30

2.4.4

Izod Impact Strength ........................................................ 31

2.4.5

Relaxation Behaviour of Polymers ................................... 32

Mechanical Properties of Particular Polymers ............................... 32 2.5.1

Polyether Ether Ketone .................................................... 32

2.5.2

Epoxy Resins ................................................................... 32

2.5.3

Polyethylene Terephthalate .............................................. 34

2.5.4

Polydiallylphthalate ......................................................... 34

2.5.5

Polyamides ....................................................................... 35

2.5.6

Polystyrene ...................................................................... 38

2.5.7

Polypropylene .................................................................. 38

2.5.8

Polyethylene ..................................................................... 39

2.5.9

Ethylene-vinyl Acetate ..................................................... 40

2.5.10 Ethylene Propylene Diene – Polypropylene – Maleic Anhydride Vulcanisates .................................................... 40 2.5.11 Polymethyl Methacrylate ................................................. 40 2.5.12 Fluoropolymers ................................................................ 40 2.5.12.1

Polyvinylidene Fluoride-clay Nanocomposites ... 40

2.5.12.2

Poly(vinylidene luoride)-TetraluroethylenePropylene ........................................................... 41

2.5.13 Natural Rubber and Isoprene Rubber .............................. 41 2.6 3

Thermal Properties of Polymers ............................................................... 53 3.1

vi

Use of Lubricating Agents in Engineering Polymer Formulations .. 41

Introduction .................................................................................. 53

Contents 3.2

Thermal Expansion Coeficient ..................................................... 57

3.3

Mould Shrinkage .......................................................................... 58

3.4

Melting Temperature or Softening Point ....................................... 59 3.4.1

Polyaryl Ether Ketone ...................................................... 60

3.4.2

Polyester Amide ............................................................... 61

3.4.3

Polyimides and Polyamides .............................................. 61

3.5

Maximum Operating Temperature ............................................... 61

3.6

Brittleness Temperature (Low Temperature Embrittlement Temperature) ................................................................................ 62

3.7

Heat Distortion Temperature ........................................................ 63 3.7.1

Heat Distortion Temperature at 0.45 MPa (˚C)................ 63

3.7.2

Heat Distortion Temperature at 1.80 MPa (˚C)................ 63

3.8

Thermal Conductivity ................................................................... 64

3.9

Speciic Heat ................................................................................. 66 3.9.1

Hot Wire Techniques ....................................................... 66

3.9.2

Transient Plane Source Technique .................................... 66

3.10

Thermal Diffusivity ....................................................................... 67

3.11

Thermal Insulation Index .............................................................. 67

3.12

Glass Transition Temperatures ...................................................... 67

3.13

Alpha, Beta and Gamma Transitions............................................. 70 3.13.1 Dynamic Mechanical Analysis ......................................... 71 3.13.2 Differential Thermal Analysis .......................................... 73 3.13.3 Infrared Spectroscopy ...................................................... 73 3.13.4 Dielectric Thermal Analysis ............................................. 73

3.14

Developments in High Temperature Plastics ................................. 74 3.14.1 Introduction ..................................................................... 74 3.14.2 Polyimides ....................................................................... 80 3.14.3 Fluorinated Polyimides .................................................... 80 3.14.4 Polyamide-imide .............................................................. 80 3.14.5 Polyether-imide ................................................................ 80

vii

Engineering Plastics 3.14.6 Polyphenylene Sulide ...................................................... 81 3.14.7 Polyxylenyl Sulide ........................................................... 82 3.14.8 Polyether Sulfone and Polyphenylene Sulide ................... 82 3.14.9 Organosilicon Polymers ................................................... 84 4

Electrical Properties of Polymers .............................................................. 91 4.1

4.1.1

Dielectric Constant .......................................................... 93

4.1.2

Dielectric Strength ........................................................... 93

4.1.3

Volume Resistivity ........................................................... 97

4.1.4

Dissipation Factor ............................................................ 97

4.1.5

Electrical Resistance and Resistivity ................................. 97

4.1.6

Surface Arc Resistance ..................................................... 97

4.1.7

Tracking Resistance ......................................................... 98

4.2

Typical Electrical Properties of a Range of Engineering Polymers . 99

4.3

Effect of Reinforcing Agents on Electrical Properties .................... 99

4.4

Applications of High Dielectric Strength Polymers ...................... 100

4.5

Effect of Reinforcing Agents on Electrical and Mechanical Properties .................................................................................... 104

4.6

viii

Introduction .................................................................................. 91

4.5.1

Glass Fibre Reinforcement ............................................. 104

4.5.2

Silica Resin Reinforcement ............................................. 104

4.5.3

Carbon Fibre Reinforced Plastics ................................... 105

4.5.4

Carbon Nanotubes ........................................................ 105

4.5.5

Carbon Black and Carbon Fibre .................................... 106

Electrical Properties .................................................................... 107 4.6.1

Dielectric Strength ......................................................... 107

4.6.2

Volume Resistivity ......................................................... 107

4.6.3

Dielectric Constant ........................................................ 108

4.6.4

Tracking Resistance ....................................................... 109

4.6.5

Failure of Electrical Properties ....................................... 110

Contents

4.7

4.8 5

6

4.6.6

Electrical Conductivity ................................................... 110

4.6.7

Electrical Resistance ....................................................... 110

Electrically Conducting Polymers ................................................ 111 4.7.1

Polyaniline ..................................................................... 111

4.7.2

Carbon Nanotubes ........................................................ 114

4.7.3

Metal containing Electrically Conductive Polymers........ 114

4.7.4

Other Conducting Polymers ........................................... 115

Fire Retardant Plastics for the Electrical Industry........................ 115

Miscellaneous Polymer Properties .......................................................... 125 5.1

Abrasion Resistance and Wear .................................................... 125

5.2

Fatigue Index .............................................................................. 130

5.3

Coeficient of Friction ................................................................. 131

5.4

Surface Hardness ........................................................................ 132

5.5

Haze, Glass and Surface Roughness ............................................ 133

5.6

Weathering Properties of Engineering Plastics ............................. 135

5.7

Chemical Resistance.................................................................... 137

5.8

Detergent Resistance ................................................................... 137

5.9

Solvent Resistance ....................................................................... 138

5.10

Hydrolytic Stability and Water Absorption ................................. 140

5.11

Gas Barrier Properties of Plastics ................................................ 141

5.12

Prediction of Polymer Service Lifetimes....................................... 144

Plastics in Automotive Engineering ........................................................ 159 6.1

Applications ................................................................................ 159 6.1.1

Polypropylene and Polyethylene ..................................... 161

6.1.2

Ethylene-propylene-diene ............................................... 162

6.1.3

Polyether Ether Ketone .................................................. 163

6.1.4

Polyesters ....................................................................... 163

6.1.5

Polyethylene Terephthalate ............................................ 163

6.1.6

Polyamides ..................................................................... 164

ix

Engineering Plastics

7

8

Polyacetal ...................................................................... 165

6.1.8

Polyphenylene Sulide .................................................... 166

6.2

Acoustic Properties of Polymers .................................................. 166

6.3

End of Life of Vehicles ................................................................ 167

6.4

Miscellaneous Applications ......................................................... 168 6.4.1

Interiors ......................................................................... 168

6.4.2

Seals ............................................................................... 168

6.4.3

Tyres .............................................................................. 169

Plastics in Aerospace .............................................................................. 173 7.1

Applications ................................................................................ 173

7.2

Glass ibre Reinforced Plastics .................................................... 174

7.3

Carbon Fibre Reinforced Nanocomposite Plastics....................... 175

7.4

Pitched Fibre Cyanate Ester Composites ..................................... 177

7.5

Recent Developments .................................................................. 177

Other Engineering Applications ............................................................. 183 8.1

General Engineering Applications ............................................... 183

8.2

Building Materials ...................................................................... 188

8.3

x

6.1.7

8.2.1

Building Insulation ......................................................... 188

8.2.2

Rooing .......................................................................... 189

8.2.3

Construction Materials .................................................. 190

8.2.4

Wood Substitute............................................................. 192

8.2.5

Ventilation ..................................................................... 192

8.2.6

Earthquake Prooing ...................................................... 192

Plastics in Electrochemical Cells .................................................. 193 8.3.1

Membranes .................................................................... 193

8.3.2

Battery Plates ................................................................. 194

8.4

Polymers in Medical Devices ....................................................... 195

8.5

Gas Barrier Properties ................................................................. 195

Contents 8.6

Foam Insulation .......................................................................... 206

8.7

Radiation Resistance of Engineering Plastics ............................... 207 8.7.1

Gamma Radiation ......................................................... 207

8.7.2

Ultraviolet Radiation ..................................................... 208

8.7.3

Electron Irradiation ....................................................... 210

8.7.4

Neutron/Gamma Irradiation .......................................... 210

Abbreviations .................................................................................................... 227 Index .............................................................................................................. 235

xi

Engineering Plastics

xii

1

Introduction

It is irst necessary to discuss what an engineering plastic is. Generally, engineering plastics are those, which are replacing conventional materials such as metals and alloys in general engineering. In addition, the term engineering plastics covers materials that have superior properties, which were not previously available in conventional polymeric materials. In this book an arbitrary decision has to be made as to what are engineering plastics and what are not. Only the following are included in the discussion. Engineering polymers also include combinations or composites of the polymers listed in Table 1.1 with reinforcing agents such as glass ibre, talc, carbon ibres, clay minerals, mica and illers such as calcium carbonate, glass beads, silica, lubricants, PTFE, silicones and molybdenum disulide. Polymers which are not generally included in this review, i.e., which have either no or borderline engineering applications include: •  Styrene-maleic anhydride •  Styrene-acrylonitrile •  Styrene-acrylonitrile-butadiene •  Phenol-formaldehyde •  Urea-formaldehyde •  Polystyrene These have only limited engineering applications in interior or under bonnet parts of automobiles, cable insulation and switchgear, lighting ixtures, battery containers, air conditioning housings, refrigerator parts and telephone handsets. A general review of some of the important applications of engineering polymers is given in Appendix 1. Applications, in general are discussed under four main headings: mechanical, electrical, thermal and others.

1

Engineering Plastics

Table 1.1 Engineering plastics •  P   olyoleins such as polyethylene (PE), polypropylene (PP) (including high molecular weight  PE) and PE-ethylene copolymers and ethylene propylene diene terpolymers •   Alkyd resins  •   Polyoxymethylene (POM; Polyacetyl) •   Polyphenylene oxide (PPO) •   Polyarylates •   Epoxy resins  •   Polyether ether ketone (PEEK) •   Polydiallyl isophthalate and polyallyl phthalate  •   Polycarbonate (PC) •   Polyesters  •   Polyethylene terephthalate (PET) •   Polybutylene terephthalate (PBT) •   Polyamides such as PA 6, PA 6,6,PA 6,9, PA 6,10, PA 11, PA 6,12 and PA 12 •   Polyether ester amide  •   Polyimide (PI) •   Polyether-imide (PEI) •   Polyamide-imide (PAI) •   Polyethylene sulide (PES) •   Polyphenylene sulide (PPS) and polyphenylene disulide •   Aromatic disulides •   Polysulfone (PSU) •   Fluorinated ethylene-propylene (FEP) copolymer  •   Polytetraluoroethylene (PTFE) •   Polyvinyl luoride •   Polyvinylidene luoride (PVDF) •   Perluoroalkoxyethylene  •   Ethylene-tetraluoroethylene •   Ethylene-chlorotriluoroethylene (ECTFE) •   Polysiloxanes

1.1 Mechanical Applications Polymers can be used in many mechanical applications and a few of these are: bearings, gears, valves, pumps, bushes, sprockets, diaphragms, wear pads, compression rings,

2

Introduction connecting rods, valve seals, air ducts, fan blades, artiicial joints, plant construction materials, pressure vessels, building materials, aircraft fuselages, automotive applications including exhaust pipes, gear box, power transmission, fuel and hydraulic fuel lines, piston rings, bumper bars, facia and fuel tanks.

1.2 Electrical Applications Polymers can also be used in many applications and a few examples are: electrical cable and wire insulations, electrical systems and components, automotive ignition, switches, relays, capacitors, transformers, resistors, printed circuit boards, bush holders, terminal blocks, electric motor parts, capacitors, telecommunications equipment, ignition components, television and radio location.

1.3 Thermal Applications Thermal applications of polymers include: heat shrinkable tubing, heat resistant parts, oven parts, oven grills, cooling systems, expansion tanks, heating systems, heat exchangers, thermal protections and high heat applications.

1.4 Miscellaneous Applications Other applications of polymers are: chemical, solvent, chemical and oil resistant parts, sterilisation, medical components, washing machine and dishwasher components, marine protection, aerospace, missiles, aircraft jet engines, helicopter, helicopter blades, gamma radiation resistant parts, sporting gear, glazing, battery cases and solar panels.

1.5 Significant Polymer Properties The mechanical properties of importance in critical engineering applications include: stiffness,  rigidity,  impact  and  impact  strength,  lexural  modulus,  elongation  and  include applications in areas such as gears, piping, automotive under the bonnet applications, aircraft and aerospace engineering power transmissions equipment, structural components and so on. Electrical properties include volume resistivity, dielectric strength, arc and tracking resistance. Applications include wire covering, ignition and switching systems, relays,

3

Engineering Plastics transformers, encapsulation of electric devices, insulation and so on, and electronically conducting polymers. Thermal properties include parameters such as expansion coeficient, maximum operating temperature and also involve the thermal stability of polymers when they are exposed to heat either during processing operations such as mouldings and also, during the service life of components. Polymers such as PEI, PSU, PI, PPS and PES  all have exceptional thermal properties. Some  of  the  types  of  polymers  that  have  been  used  for  engineering  parts  and/in  engineering applications are shown in Table 1.2.

Table 1.2 Applications of unreinforced engineering polymers Automotive applications Car bumpers

PP, PA 6,6, methylene-PP and copolymers

Car facias

Ethylene-propylene, elastomers and PPO

Radiator grills

PPO

Fan blades

POM (polyacetal) and PMMA

High tolerance parts

PET

Under body components

PSU, PBT and PEI

Fuel tanks and lines

PA 6 and PA 12

Door closures

PA 6

Timing chains

PA 6,6 and PA 6,9

Hoses

PA 11

Injection moulded parts

PA 12 and PA-PPO alloy

Gears

PA-ABS alloy

Instrument panels

ABS-PC alloy

Piston rings and valve seals

PI and PTFE

Engine parts

PAI

Valve and pumps

PSU, PAI, PTFE, ECTFE, ethylene-tetraluoroethylene and  chlorotriluoroethylene copolymer

Non-stick valves

FEP

Bearings, gears, bushings and  cams

Ultra-high molecular weight polyethylene, POM (polyacetal),  PA 6, PA 6,6, PA 6,9, PA 11, PA 12, PAI, PU, PTFE and  PVDF

4

Introduction

General engineering applications Guards

PEEK, PC, polyester resins, PMMA and PA 6,12

Precision machining

PA 12 and PSU

High rigidity applications

HDPE

Impellers

PA-ABS alloy

Impact resistant parts

PP

Power tool components

Ethylene-propylene elastomer

Load bearing parts

POM (polyacetal)

Shock resistant parts

PU

High strength parts

Polyester resin

Piping

Low-density polyethylene, HDPE, crosslinked PE, ethylenePP copolymer, polyester resins, polyether ester amide and PVDF

O-rings

Chlorotriluoroethylene copolymer

Gaskets

PTFE, polychlorotriluoroethylene copolymer

Aircraft airbrakes

PA 12

Steel replacement

PSU

Artiicial joints

PP

Abrasion resistant parts

POM (polyacetal), PA 6,12 and PU silicones

Building applications

Polyester sheet

Glazing safety shields

PC

Air ducts

PA 12

Low water absorption

PA 6,12

ABS: Acrylonitrile-butadiene-styrene HDPE: High-density polyethylene PMMA: Polymethyl methacrylate PU: Polyurethane Source: Author’s own iles

5

Engineering Plastics

6

2

Mechanical Properties of Polymers

2.1 Review of Mechanical Properties Mechanical properties of some unreinforced engineering polymers are shown in Table 2.1.

Table 2.1 Mechanical properties of polymers Polymers

Tensile strength (MPa) ASTM D638 [1]

Flexural Elongation Strain modulus at break at (modulus of (%) yield elasticity) (%) (GPa)

Notched Surface Izod hardness impact Strength (kJ/m)

Comprehensive strength ASTM D695 [2] (MN/m2)

LPDE

10

0.25

400

19

1.064

SD 48

-

HDPE

32

1.25

150

15

0.15

SD 68

16.5

Crosslinked PE

18

0.5

350

N/Y

1.064

SD 58

-

PP – calcium carbonate illed

26

2

60

N/Y

0.05

RR 85

59−69

Ethylene-PP

26

0.6

500

N/Y

0.15

RR 75

-

Polymethylpentene/ 28 calcium carbonate

1.5

15

6

0.04

RR 70

-

Carbon/hydrogen containing polymers

Styrene-butadiene

28

1.6

50

N/Y

0.08

SD 75

-

Styrene-ethylenebutylene-styrene

6

0.02

800

N/Y

1.064

SA 45

-

High impact polystyrene

42

2.1

2.5

1.8

0.1

RM 30

27−62

1.6

-

-

RM 80

79−110

PS, general purpose 34

3

Oxygen containing polymers Epoxies, general purpose

60-80

3-3.5

4-8

N/A

0.5

RM 113

-

Acetal (polyoxyethylene)

50

27

20

8

0.10

RM 109

-

Polyesters (bisphenol), polyester laminate (glass illed)

280

16

1.5

N/A

1.064

RM 125

-

9

2

N/A

0.4

RM 125

-

Polyester (electrical 40 grade)

7

Engineering Plastics Polybutylene phthalate

52

2.1

250

4

0.06

RM 70

-

PET

55

2.3

300

3.5

0.02

RM 30

-

PEEK

92

3.7

50

4.3

0.083

RM 99

-

Diallylisophthalate

82

11.3

0.9

N/A

0.37

RM 112

-

Diallylphthalate

70

10.6

0.9

N/A

0.41

RM 112

-

Alkyd resin glass ibre, reinforced

72

8.6

0.8

N/A

0.24

RM 125

Polyarylates

68

2.2

50

8.8

0.29

RR 125

-

PC

50

2.1

200

3.5

0.05

RM 70

-

PPO

65

2.5

60

4.5

0.16

RR 119

-

Phenolformaldehyde

45

6.5

1.2

N/A

0.024

RM 114

-

Styrene-maleic anhydride

52

3

1.8

2

0.03

RL 105

-

Cellulose acetate

30

1.7

60

4

0.26

RR 71

-

Cellulose propionate

35

1.76

60

4

0.13

RR 94

-

Cellulose-acetatebutyrate acrylics

70

2.9

2.5

N/A

0.02

RM 92

-

EVA

17

0.02

750

N/A

1.064

SA 85

-

Nitrogen containing polymers PA 6

40

1

60

4.5

0.25

SD 75

-

PA 4,6

100

1

30

11

0.1

SD 85

-

PA 11

52

0.9

320

20

0.05

RR 105

-

PA 6,9

50

1.4

15

10

0.06

SD 78

-

PA 12

50

1.4

200

6

0.06

RR 105

-

PA 6,6

59

1.2

60

4.5

0.11

RR 90

-

PA 6,12

51

1.4

300

7

0.04

RR 105

-

Nylon/ABS alloy

47

2.14

270

6

0.85

RR 99

-

PI

185

4.58

12

8

0.13

RM 109

-

PA

72

2.45

8

4

0.08

RM 100

-

PEI

105

3.3

60

8

0.1

RM 109

-

PU thermoplastic elastomer

24

0.003

700

N/Y

1.064+

SA 70

-

Ether-ester-amide elastomer

57

10

0.6

N/A

0.02

RM 115

-

Styreneacrylonitrile

72

3.6

2.4

3.5

0.02

RM 80

-

ABS

34

2.1

6

2

0.18

RR 96

-

Acrylate-styreneacrylonitrile

35

2.5

10

3.3

0.1

RR 106

-

PTFE

2.5

0.70

400

70

0.16

RM 69

-

PVF

40

1.4

150

30

0.18

SD 80

-

Polyvinylidene luoride

100

5.5

6

N/A

0.12

SD 90

-

Fluorine containing polymers

8

Mechanical Properties of Polymers

29

0.7

300

85

1.064+

SD 60

-

Ethylene28 tetraluoro-ethylene

1.4

150

15

1.064+

RR 50

-

Ethylenechlorotriluoroethylene

30

1.7

200

5

1.064+

RR 93

-

Fluorinated ethylene-PP

14

0.6

150

6

1.064+

RR 45

-

Chlorinated PVC

58

3.1

30

5

0.06

SA 70

-

Unplasticised PVC

51

3

60

3.5

0.08

RR 110

-

Plasticised PVC

14−20

0.007−0.03

280−95

N/A

1.05+

SA 85

-

PPS

91

13.8

0.6

N/A

0.6

RR 121

-

PSU

70

2.65

80

5.5

0.07

RM 69

-

PES

84

2.6

60

6.6

0.084

RM 85

-

Silicones

28

3.5

0.02

RM 80

-

Perluoroalkoxyethylene

Chlorine containing polymers

Sulfur containing polymers

Silicon containing polymers 2

N/A

+

A higher impact energy than the test can generate. These are typical room-temperature values of notched Izod impact strength. A material that does not break in the Izod test is given a value of 1.06 + kJ/m. ASTM: American Society for Testing and Materials ABS: Acrylonitrile-butadiene-styrene EVA: Ethylene-vinyl acetate HDPE: High-density polyethylene LDPE: Low-density polyethylene N/A: Material is brittle and does not exhibit yield point N/Y: Material is ductile and does not exhibit yield point PA: Polyamide(s) PC: Polycarbonate PE: Polyethylene PEI: Polyether-imide PEEK: Polyether ether ketone PES: Polyether sulfone PET: Polyethylene terephthalate PI: Polyimide PP: Polypropylene PPO: Polyphenylene oxide PPS: Polyphenylene sulide PS: Polystyrene PSU: Polysulfone PTFE: Polytetraluoroethylene PU: Polyurethane PVC: Polyvinyl chloride PVF: Polyvinyl luoride RL: Rockwell L hardness RM: Rockwell M hardness (hard) RR: Rockwell R hardness SA: Shore A hardness (soft) SD: Shore D hardness Source: Author’s own iles

9

Engineering Plastics Some engineering polymers have exceptional mechanical properties as illustrated in Table 2.2 and 2.3, which list polymers with outstandingly high tensile strength and lexural modulus (Table 2.2) and those with outstandingly high elongation at break (Table 2.3). In the case of tensile strength only polymers with values above 70 MPa are listed in Table 2.2. Similarly, for elongation at break, only polymers with elongations exceeding 400% are listed in Table 2.3.

Table 2.2 Identification of polymers with outstanding tensile strength and flexural modulus Polymer

Tensile strength (MPa) 280

Flexural modulus (GPa) 16

Elongation at break (%) 1.5

Strain at yield (%) N/R

Notched Izod (kJ/m) + 1.06

Polyester, sheet moulding compound

70

11

2.5

N/R

0.8

PA 4,6

100

1

30

11

0.1

Polyesters (bisphenol polyester laminate) glass illed

10

Excellent or very good performance Impact strength (when compared to epoxies)

Poor performance

Heat resistance, solvent resistance, elongation at break High lexural More modulus, expensive heat than distortion polyesters. temperature, Dielectric resistance constant, to UV and dielectric gamma strength, radiation lame and high spread, toughness hydrolytic stability properties are poor. More elongated at break Reasonable Moisture heat absorption distortion temperature and good chemical resistance

Mechanical Properties of Polymers PVF (20% carbon ibre reinforced)

100

5.5

6

N/R

0.12

High tensile strength, lexural modulus, heat desorption temperature, detergent resistance and hydrolytic stability -

Elongation at break, gamma ray resistance, dielectric properties, surface inish and toughness

Epoxies 60−80 3−3.5 4−8 8 0.1 Diallyl 82 11.3 0.9 N/R 0.37 isophthalate PEI 105 3.3 60 8 0.13 Styrene72 3.6 2.4 3.5 0.03 acrylonitrile PPS 91 13.8 0.6 N/R 0.6 PSU 70 2.85 80 5.5 0.07 PES 84 2.6 60 8.6 0.084 + : A higher impact energy than the test can generate. These are typical room-temperature values of notched Izod impact strength. A material that does not break in the Izod test is given a value of 1.06 + kJ/m. N/R: Not reported UV: Ultraviolet Source: Author’s own iles

11

12

6

55

17

24

50

51

52

Styrene-ethylenebutylene-styrene

PET amorphous

Ethylene-vinyl acetate, (25%) vinyl acetate

Polyurethanethermo-plastic elastomer

PA 12

PA 6,12

PA 11

LDPE

0.9

1.4

1.4

0.003

0.02

2.3

0.02

Flexural modulus (GPa) 0.25

320

300

200

700

750

300

800

Elongation of break (%) 400

20

7

6

N/Y

N/Y

3.5

N/Y

Strain at yield (%) 10

0.05

0.04

0.06

1.06+

1.06

0.02

1.06

Notched Izod (kJ/m) 10.06

Elongation at break, impact strength, heat resistance, fatigue index, toughness

detergent resistance and elongation at break

Elongation at break, low water absorption, toughness, dielectric strength Low water absorption,

Elongation at break, low temperature characteristics and detergent resistance

Elongation at break, chemical resistance, electrical properties, cost and toughness Elongation at break, low temperature properties, electrical properties and toughness Elongation at break, stiffness detergent resistance, electrical properties and elongation at break Elongation at break, strain at yield, toughness and cost

Excellent or very good performance

dissipation factor, lammability, lexural modulus Cost and impact strength

Low heat distortion temperature,

High cost, strength and heat resistance

lexural modulus

Tensile strength, chemical resistance, dissipation factor, lammability, heat distortion temperature and lexural modulus Tensile strength and

Tensile strength, stiffness, lammable, UV resistance and environmental stress cracking Abrasion resistance tensile strength, lame spread, lexural modulus Limited hydrolysis resistance and high mould shrinkage

Poor performance

Table 2.3 Identification of polymers with outstanding elongation at break

Tensile strength (MPa) 10

Polymer

Engineering Plastics

70

68

PSU

Polyacrylates

2.2

2.65

10.6

50

80

0.9

0.9

0.6

60

15

55

N/A

N/A

N/A

8

1.06+

0.07

0.41

0.37

0.031

0.01

Tensile strength, lexural modulus, notched Izod, detergent resistance, heat distortion temperature, tracking resistance, and UV radiation High temperature performance, electrical properties, hydrolytic resistance, tensile strength and dimensional stability Impact strength, heat resistance and UV resistance

Stress cracking with hydrocarbons and needs 350 °C processing temperature

Surface inish

Volume resistance, dielectric strength, dissipation factor, lammability, hydrolytic stability, high cost and elongation break

Stress cracking with chlorinated solvents, notched impact strength, high cost, tracking resistance, lexural modulus and toughness Flexural strength and lexural Electrical properties and modulus notched Izod Tensile strength, lexural Volume resistance, dielectric modulus, notched Izod, detergent strength, dissipation factor, resistance, heat distortion lammability, hydrolytic temperature, tracking resistance, stability, high cost and and UV radiation elongation break

Tensile strength, limiting oxygen index, detergent resistance, gamma ray and UV resistance, and cost

N/A: Material is brittle and does not exhibit a yield point. N/Y: Material is ductile and does not exhibit a yield point. + : A higher impact energy than the test can generate. These are typical room-temperature values of notched Izod impact strength. A material that does not break in the Izod test is given a value of 1.06 + kJ/m. Source: Author’s own iles

70

11.3

82

Diallyl phthalate

13.8

91

PPS, glass reinforced Diallyl isophthalate (long glass ibre reinforced)

1.4 33

50 105

PA 6,9 PEI

Mechanical Properties of Polymers

13

Engineering Plastics A great deal of experimental work has been published in recent years on the mechanical properties of unreinforced and reinforced engineering polymers. Examples of this work are reviewed in the next section.

2.2 Mechanical Properties of Unreinforced Polymers

2.2.1 Polyolefins Hammond and co-workers [3] studied the effects of elongation, time and temperature upon the concentrations of carbonyl and vinyl groups formed during the plastic deformation of HDPE using infrared spectroscopy. Samples that have been elongated in various atmospheres are also described. The morphology of lamellar crystallised polymers is taken to involve both folded chains and those linking adjacent lamellar cores. It is dificult to reconcile this model with the alternate proposals to explain plastic deformation at the molecular level unless one is prepared to accept that numerous chain ruptures occur during the process. It is conirmed that this is not the case. An alternative explanation is proposed for the processes that occur when spherulitic materials become oriented and ibrillar. Hammond and co-workers [3] proposed and provided evidence that mechanical work is concentrated into very small volumes in the neck region leading to localised melting and subsequent re-crystallisation. As a piece of PE was drawn thinner in the presence of oxygen then the concentration of carbonyl and vinyl groups were observed to progressively increase as shown in Figure 2.1. Poly Hi Solidur Plastics India Limited [4] developed products for use on the Indian Railways based on ultra-high molecular weight PE (UHMWPE; Hoechst’s Hostalen GUR). The base polymer is mixed with patented additives and uses a computer controlled sintering process and sophisticated fabrication methods to produce a material which is claimed to have much higher values for a number of technically important properties such as wear, chemical and water resistance, impact strength and dynamic coeficient of friction. The growth of the market for UHMWPE products is briely discussed, and the applications targeted by Poly Hi Solidur Plastics are discussed. Merry and co-workers [5] used an axisymmetric tension test to perform constant stress tests and compare the creep response of new and old HDPE geomembranes. A 36-h constant stress creep test was performed on new HDPE using a temperature range of 2−53 °C and stresses ranging from 2−15 MPa. Excess material was then stored in a laboratory for an additional seven years, after which time tests on ‘old’ geo-membranes were performed. Because the experimental results could not be compared directly, an adaption of the Singh-Mitchell creep model for soil, which is a rate process equation, 14

Mechanical Properties of Polymers was used to characterise the observed stress-strain-time-temperature response from the constant stress creep tests over four logarithmic decades of time. The model, which was calibrated using results on ‘new’ geo-membranes, was used to predict the response of the ‘old’ geo-membranes. It is shown that there was essentially no difference in the creep response of the old geomembranes.

Thickness (mm) 1.0

8

0.5 0.4 0.30 0.25 0.20

0.150

0.125

0.100

7 Carbonyl, 1,742 cm–1

Conc. (1018 groups/cm3)

6 5 4

Vinyl, 909 cm–1

3 2 1 0 0

1

2

3

4

5

6

7

8

9

10

1/Thickness (mm–1)

Figure 2.1 New end-group concentrations as a function of original thickness for a draw ratio of 0.76 in oxygen at 20 °C. Reproduced with permission from C.L. Hammond, B.G. Lator, W.F. Maddams, P.J. Hendra and H.A. Willis, Polymer, 1988, 29, 1, 49. ©1988, Elsevier [3]

Mills and Gilchrist [6] subjected PP foam beads to oblique impacts, in which the material was compressed and sheared. This strain combination could occur when a cycle helmet hit a road surface. The results were compared with simple shear tests at low strain rates and to uniaxial compressive tests at impact strain rates. The observed shear hardening was greatest when there was no imposed density increase and practically zero when the angle of impact was less than 15°. The shear hardening appeared to be a unique function of the main tensile extension ratio and was caused by

15

Engineering Plastics the polymer whereas the volumetric hardening was due to the isothermal compression of the gas in the cell foam. Foam material models for inite element analysis needed to be reformulated to consider the physics of the hardening mechanisms, so that their predictions are reliable for foam impacts in which shear occurs.

2.2.2 Polyphenylene Oxide PPO is an important engineering thermoplastic. This is due to its high tensile strength (65 MPa) and creep resistance. In particular, Chan and co-workers [7] discuss the tensile strength of Noryl resin which is a blend of poly(2,6-dimethyl-1,4 phenylene oxide) and PS.

2.2.3 Epoxy Resin Numerous studies [8-19] have been conducted on epoxy resins, which are essentially, high tensile strength materials (up to 80 MPa, see Table 2.2). Properties discussed include tensile storage modulus [20], tensile compression, bending and impact, electrical, thermal, corrosion and solvent resistance, viscoelastic, vitriication. Applications of epoxy resins include sporting goods [21], bolted joints and adhesives [13]. Tasdemir and Yildirim [22] showed that rigid plastics such as epoxies, PS, PVC, polymethyl methacrylate (PMMA), PP, PC, unsaturated polyester resins and PA can be toughened and their impact properties improved by the incorporation in the formulation of 5−20% of a rubbery elastomer such as ABS terpolymer.

2.2.4 Acrylic Resins Properties of acrylic resins, which have been investigated include hardness, and their acoustic properties when deformed by tensile stress [23]. The ultrasonic velocities of PMMA in steady stress-strain states were measured in the frequency range 100 MHz to 1 GHz. The ultrasonic velocities decreased with increasing strain and the ratio of the decrease increased with increasing strain rate. This result indicated that the crazing residues still remained in the steady stress-strain states and the amount of the residues depended on the strain rate. The velocity dispersion was observed around 400 MHz for virgin and deformed PMMA and reproduced according to the dispersion map for methyl group relaxation in PMMA. The relaxation frequency and strength were

16

Mechanical Properties of Polymers independent of the applied stress and strain. The viscoelastic and plastic deformation had little effect on the gamma relaxation. Ethylene-acrylate copolymers have been used as modifying agents to improve impact strength and compatibility of other polymers [24, 25].

2.2.5 Polyether Ether Ketone Polyether ether ketone (PEEK) has been used extensively in engineering applications because of its high dimensional stability. Polyacryl ether ketone is a semi-crystalline, high performance thermoplastic widely used in engineering applications. Understanding the thermal and rheological behaviour of this polymer is critical for predicting its process mouldability, post-processing properties and structural behaviour. A study by Yuan and co-workers [26] discusses the inluence of molecular weight on the thermal and rheological behaviour of polyarylether ketone. Melt temperature, crystallisation phenomena and rheological properties were compared for polymers with different molecular weights. Zhou and co-workers [27] studied the effects of surface treatment on the mechanical and thermal properties of composites comprising calcium carbonate particles with varying proportions of PEEK. Tensile impact and lexural testing were carried out and the effect of particle size, loading and surface treatment on deformation and crystallinity was investigated. Melo and Radford [28] carried out an investigation into the feasibility of using an approach with a reduced number of measured parameters for determining the threedimensional viscoelastic characteristics of transversely isotropic materials over a range of temperatures. Tests were carried out on a grade of PEEK at temperatures ranging from -20 to 120 °C using dynamic mechanical analysis (DMA). The viscoelastic data obtained were used to predict the properties of unidirectional, off-axis beam and a comparison was made with the experimental indings.

2.2.6 Polyethylene Terephthalate Koh and co-workers [29], investigated the mechanical and thermal properties of glass reinforced PET used as printer parts. This study emphasised the importance of the moulding processes in achieving optimised mechanical properties.

17

Engineering Plastics

2.2.7 Polyimides Fan and co-workers [30] demonstrated that the tensile strength and modulus of PI ilms produced by copolycondensation of 3,5-diamino-benzonic-4´-biphenyl ester, 4,4ʹ-diamino-biphenyl ether and 3,3ʹ,4,4ʹ-oxydiphthalic dianhydride improved by 270 to 300%, respectively, as a result of in situ, self-reinforcement caused by the introduction of a side chain mesogenic unit. In parallel with this, the thermal expansion coeficient of ilms decreased by 40%. The 5% weight loss temperature was 520 °C. Other studies of PI included dynamic light scattering characterisation of molecular weight distributions of unfractionated PI [31] and the characterisation of weight average molecular weight of PI crosslinked with hexamethylene diisocyanate. Abraham and co-workers [32] described measurements of the tensile shear lap strength of bonded specimens of an epoxy imide resin derived from N-(4-carboxyphenyl) trimellitimide bonded to stainless steel. The effect of epoxy resin type on adhesive strength of the PI-aluminium bond, are also discussed. Siddiqu and Wu [31] used a dynamic laser light scattering method to characterise an unfractionated PI in chloroform at 25 °C. The relatively small angular and concentration dependencies and translational diffusion coeficients measured by this technique enabled the PI to be characterised from only one measurement at a inite concentration and small scattering angle. Thus, this method could be used to characterise the molecular weight distribution of PI from the measured line-width distribution. Habas and co-workers [33] carried out a rheological study of mechanical relaxations in a high performance PI. Three rheological transitions were studied in a crosslinked nadimide resin using thermomechanical analysis in the range -150 to 400 °C. The irst transition was at 300 °C and is the glass transition of the crosslinked compound. The other two transitions at -100 and 70 °C were due to localised motions of the rigid segments made up of aromatic structures and imide rings.

2.2.8 Fluorinated Polyimides Matsuda and Ando [34] discuss the control of molecular orientation and anisotropic optical properties of uniaxially drawn luorinated PI ilms based on pyromellitic dianhydride and 2,2ʹ-bis-(triluoromethyl)-4,4ʹ-diaminobiphenyl used for light wave circuit applications. Methods of controlling in-plane birefringence in PI ilms were developed and a PI waveplate was prepared. This waveplate was inserted into a groove formed in an arrayed waveguide grating, the polarisation dependence of which was completely eliminated.

18

Mechanical Properties of Polymers

2.2.9 Polyamide-imide This is an engineering plastic designed for thermal/electrical applications requiring high dimensional stability. This material exhibits superior electrical and mechanical performance at continuous use temperatures ranging from -60 to 260 °C. Pyropel HDT polyamide-imide (PAI) produced by Albany International [35] has enhanced properties without the need for post-curing. These materials exhibit greater dimensional stability and improved chemical resistance throughout their usable temperature range. Pyropel HDT will not soften or creep as a thermoplastic does and has a heat delection temperature signiicantly higher than those of many engineering thermoplastics. Applications include thermal and electrical insulators, bushings, standoffs, plasma cutting/welding insulator ports and containers for semiconductor chip testing. Park and co-workers [36] used PAI-polydimethylsiloxane nanocomposites and characterised the mechanical, surface and thermal properties of these nanocomposite ilms. Elongation and toughness of these ilms was increased relative to the PAI but the tensile strength was decreased. Thermal properties showed a greater thermal weight loss initially, but char concentration in an oxygen atmosphere at 100 °C was increased.

2.2.10 Polyamides La Mantia [37] studied the relationship between the mechanical properties of recycled PA 6 and the recycling conditions used. Samples were recycled up to ive times. It was found that the addition of an antioxidant between each extrusion reduced the effects of hydrolytic and thermomechanical degradation on polymer molecular weight, and thus on viscosity and mechanical properties. Tjong and Meng [38] studied the blend behaviour of PA 6 and a thermotropic liquid crystalline polymer (based on 2, 6-hydroxynaphthoic acid and p-hydroxybenzoicacid) compatibilised with maleic anhydride grafted PP using scanning electron microscopy (SEM), the drop weight Charpy impact test and static tensile and DMA measurements. Blending was carried out by direct injection moulding of PA 6,6-maleic anhydride with liquid crystalline polymer pellets at 285 °C. The tensile strength and modulus increased with increasing liquid crystalline polymer content and the mechanical properties were above predictions from the rule of mixtures. The increase in tensile strength and modulus was correlated with the formation of liquid crystalline polymer ibrils with large aspect ratios in both the skin and core sections of the blends. The impact fracture toughness decreased signiicantly with the addition of small concentrations

19

Engineering Plastics of liquid crystalline polymer, whereas the impact toughness increased with liquid crystalline polymers concentrations above 30%. Tajima and co-workers [39] studied the relationship between drawing stress and structural development of high molecular weight PA 6. Both alpha and gamma crystals were formed in the drawn samples. The fraction of alpha crystals in the crystalline phases increased with increase in the drawing stress leading to an increase in tensile modulus. The maximum drawing stress found was about 3.5 MPa when the fraction of alpha crystals was 0·75. Friction was increased further by heat treatment under high stress. Annealing of drawn samples lead to oriented amorphous chains and gamma crystals being transformed to alpha crystals with an increase in tensile modulus up to 18.6 GPa. Bates and co-workers [40] in studies of vibration welding of PA 6 to PA 6,6 showed that weld strengths were improved by increasing meltdown and decreasing weld pressure. In general, higher weld strengths are achieved when both PA were melted. Gröning and Hakkarainen [41] studied the correlation between degradation product pattern and changes in the mechanical properties during the thermo-oxidation of in-plant recycled PA 6,6. Headspace solid-phase micro-extraction with gas chromatography (GC)-mass spectrometry (MS), tensile strength, differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR) spectroscopy were used in this investigation. The low molecular weight degradation products extracted from the recycled PA were identiied, the inluence of recycling on the formation of the degradation products was explored and changes in the PA matrix as a result of recycling and thermo-oxidation are discussed. In general, plant recycling of PA 6,6 produced an increased susceptibility to thermo-oxidation and a decrease in tensile strength. The recycled materials had a shorter induction period toward oxidation, and their mechanical properties deteriorated faster than the mechanical properties of the virgin material. Degradation products were found for recycled materials after oxidation times shorter than those for virgin material. Furthermore, larger amounts of degradation products were formed in the recycled materials. The high sensitivity of solid-phase micro-extraction followed by GC-MS as an analytical tool was demonstrated because it was able to detect changes caused by oxidation considerably earlier than the other methods such as DSC and FT-IR. Four groups of degradation products, cyclic imides, pyridines, chain fragments and cyclopentanones were identiied in thermo-oxidised PA 6,6. After 1,200 h of thermooxidation, 1-pentyl-2,5-pyrrolidinedione (denoted by R3 in Figure 2.2) was the most abundant degradation product. Approximately four times more 1-pentyl-2,5-

20

Mechanical Properties of Polymers

Relative Peak Area (%)

pyrrolidine dione was formed in PA recycled three times than in virgin PA. Pyridines and chain fragments behaved toward oxidation and repeated processing like cyclic imides, that is, their amounts increased during oxidation, and larger amounts were formed in recycled materials than in virgin material. The cyclopentanones were already present in un-aged material, and their amounts decreased during oxidation.

600 500 V R1 R2 R3

400 300 200 100 0 25

100 500 1,200 Ageing Time (hours)

Figure 2.2 Relative peaks are of 1-pentyl-2,5-pyrrolidinedione (denoted by R3) extracted from virgin and recycled PA 6,6 after 25, 100, 500 and 1,200 h of thermo-oxidation at 100 °C. Reproduced with permission from M. Gröning and M. Hakkarainen, Journal of Applied Science, 2002, 86¸ 13, 3396. ©2002, Wiley [41]

At the beginning of the oxidation, 1-pentyl-2,5-pyrrolidine dione was found only at trace levels, but after 1,200 h, its relative peak area had increased drastically, making it the most abundant degradation product. The increase was the same for both virgin and recycled materials. Substantially more 1-pentyl-2,5-pyrrolidine dione was formed from the recycled materials than from the virgin material. There was a good correlation between the recorded degradation product pattern and the changes in mechanical properties during the thermo-oxidation. Figure 2.3 shows the tensile strength and the amount of the most abundant thermo-oxidation product, 1-pentyl-2,5-pyrrolidine dione. The formation of 1-pentyl-2,5-pyrrolidine dione as a function of the thermo-oxidation time was less for the virgin material recycled once. Longer oxidation times were required to detect changes in the tensile strength, whereas differences in the degradation product patterns could already be seen during the irst 100 h with the micro-extraction GC-MS method. When the induction

21

Engineering Plastics

100

400

80

300

60

200

40 100

20

0

0 25

100

500

1200

Relative abundance (%) of 1-pentyl-2,5-pyrrolidinedione

Tensile strength (MPa)

period was surpassed, the tensile strength of PA 6,6 decreased rapidly. At the same time, a large amount of 1-pentyl-2, 5-pyrrolidine dione was formed in the material. Also, the number and amount of the other thermo-oxidation products increased simultaneously in the recycled samples, and a large number of chain fragments were formed between 100−500 h of oxidation and this coincided with the rapid decrease in mechanical properties.

100

400

80

300

60

200

40 100

20

0

0 25

100

500

Ageing time (hours) (b)

1200

Relative abundance (%) of 1-pentyl-2,5-pyrrolidinedione

Tensile strength (MPa)

Ageing time (hours) (a)

Figure 2.3 Loss of tensile strength versus the formation of 1-pentyl-2, 5-pyrrolidine dione during 1,200 h of thermo-oxidation of (a) virgin and (b) once recycled PA 6,6 at 100 °C. Reproduced with permission from M. Gröning and M. Hakkarainen, Journal of Applied Science, 2002, 86¸ 13, 3396 ©2002, Wiley [41]

22

Mechanical Properties of Polymers Chern and co-workers [42] studied tensile properties and elongation of PA containing adamantyl and diadamantyl moieties in the main chain. Leblanc and Sederel have reported on additives that are available for the improvement of the rheological properties of blow moulded engineering PA resins [43]. Such additives can be used to increase melt toughness. Researchers from Bayer [44] developed Durethan grades of PA speciically for use in the water injection moulding process. No hydrolytic degradation takes place when the hot melt comes into contact with water. These particular grades are particularly resistant to conventional engineering coolants and, thus, are used in applications in automotive under body applications. Van Ruiten and co-workers [45] studied the drawability and attainable mechanical properties of PA 4,6 yarn using true stress-strain curves. The concept of the molecular network was applied to an analysis of these ibres and yarns and the mechanical properties of yarns with different draw ratios was evaluated in terms of the network draw ratio, which was determined by matching true stress-strain curves. The validity of the molecular network concept for these yarns and its suitability for predicting ibre drawability was assessed. A method for predicting the maximum attainable tenacity of drawn yarns under given drawing conditions from precursor mechanical properties is proposed. Jakleweiz and co-workers [46] discussed the friction and scratch resistance of PA 6 modiied with ionomeric ethylene-methacrylic acid copolymer with increasing copolymer content. The dynamic coeficient of friction and scratch resistance and Young’s Modulus decreased and the thermal expansion increased with the addition of the copolymer.

2.2.11 Polyurethanes Lin and co-workers [47] reinforced PU elastomers with an entirely rigid aromatic polyamide, poly(m-phenyleneisophthalamide). The block copolymers formed exhibited glass transition temperatures (Tg) under 0 °C. Such block copolymers have improved reinforcing affect as shown by both their tensile strength and elongation when compared with the virgin PU. Expandable graphite when used as lame retardant in polyisocyanurate-PU leads to a marked decrease in compression strength and a signiicant increase in thermal conductivity [48].

23

Engineering Plastics

2.2.12 Polyphenyl Sulfone This polymer has a balance of strength, dimensional stability, electrical insulation and thermal conductivity, which is necessary to render it as a replacement for aluminium in demanding medical mouldings [49].

2.3 Reinforced Plastics Some engineering applications of polymers reinforced with glass ibre and carbon ibres are shown in Tables 2.4 and 2.5. It is seen that there are wide ranges of applications particularly in glass ibre, carbon ibre and nanotubes. Many of these applications require polymers, which have a particularly high standard of properties, for example, stability in impact and tensile properties, thermal properties, dimensional stability and, chemical and oil resistance.

2.3.1 Glass Fibre Reinforcement Applications of glass ibre reinforced plastics are reviewed in Table 2.4.

2.3.2 Applications of Carbon Fibre Reinforcement Generally speaking, the incorporation of 30% carbon ibre into a polymer produces a high strength plastic useful for structural compounds and for engineering applications. Applications include automotive, bearings, valves, and so on, and are shown in Table 2.5. Carbon nanotubes (CNT) are being increasingly used for the reinforcement of plastics. These include, epoxy resins [49, 50, 75], PA [69, 70, 76, 77], PI [71], polysilsesquioxane [72], polycaprolactone [73], polyethylene oxide [78], PE [7881], PU [82], EVA [83], polyhydroxybutyrate-co-hydroxyvalerate [84], sulfonated polyarylene sulfone [85].

2.3.3 Other Reinforcing Agents A wide range of other reinforcing agents have been used to improve the mechanical properties of polymers. These include clays, calcium carbonate, silica, talc, alumina (see Table 2.6).

24

Mechanical Properties of Polymers

Table 2.4 Applications of glass fibre reinforced plastics (% glass fibre in parenthesis) Polymer PP (20−38%) PET (35−50%)

Epoxy resins PEEK (20−35%) Polyoxymethylene (polyacetal 30%) PPO (10%) Polydiallyl isophthalate PC (20%) Polybutylene terephthalate (10-30%) PA 6 (30%) PA 6,10 (30%) PA 6,6 (60%) PA 11 (30%) PA 6,12 (10−30%) PA 12 (30−50%) PI (40%) PAI PEI (10%) PEI (30%) PPS (40%)

PSU (10−30%) PES (30%) PTFE (15−25%) Perluoroalkoxyethylene (20%) Ethylene-tetraluoroethylene (10−30%) Fluorinated ethylene-propylene Source: Author’s own iles

Applications Automotive under bonnet [50-54] Gears, sprockets, propellers, auto bumpers, auto ignition, auto exterior parts, water pumps, windscreens and auto wiper blades [50, 55-61] Power transmission equipment, building products and pressure vessels [62, 63] Automotive applications [64], high stability components of structural housing [65] Gears, bearings and bushes Automotive instrument panels Pump impellers Replacement for metal parts Automotive distributor caps and engineering parts Automotive parts and wind turbine blades Engineering, gears, cams, bearings and valve seals [55] Parts requiring high strength and stiffness [55] Fan blades, gears and precision engineering parts Mechanical parts, low water absorption and high strength applications High precision applications, e.g., fan blades, rigid dimensional stability applications, bushes and bearings Gear boxes Valve plates, pistons, gears and rotors [52] Cooling fans, gears, automotive under body applications and fuel systems Explosion proof containers, automotive under body applications, heat exchanges and fuel systems Automotive under body applications [59], parts exposed to oil, petrol and hydraulic luids, pumps, valves, precision engineering parts and exhaust emission control Pumps, valves, petrochemical industry and automotive under body applications Automotive under body applications, gear box parts, air ducting and car heater fans Wear pads and piston rings Pipes and bearings Bearings, valves and gears Valves

25

Engineering Plastics

Table 2.5 Uses of 30% carbon fibre reinforced plastics Polymer PEEK Polyoxyethylene (polyacetal) PC Polybutylene PA 6 PA 6,6 PA 6,10 PA 6,12 PPS PSU Ethylenetetraluoroethylene PVF PTFE Epoxy resins

Uses Pumping impellers and bearing bushes Bearings, cams and gears High strength plastics Applications requiring ultra-high strength and stiffness Bearings and high strength structures Connecting rods Precision engineering parts Precision engineering parts and housing valves High strength structures and cam parts Automotive under bonnet applications, chemical plant pumps, valves and pump impellers Bearings, seal rings, piston rings, valve plugs and compression rings

Bearings, nuts and pump rotators Valve bodies [64, 66-73] Structural components, boat hulls, chemical engineering plant, pressure vessels, aerospace structural components, helicopter blades and racing cars [74] PES Aerospace applications, e.g., nose cones and ducts and pump impellers Source: Author’s own iles

Table 2.6 Review of published work on miscellaneous reinforcing agents and fillers Polymers

Reference Filler - calcium carbonate

Sulfonated PEEK ABS PP LDPE/linear-LDPE components PP-EVA blends

[27] [86] [86, 87] [88] [89, 90] Filler clay

PA 6 PA 6,6 PA 6 PA 12 Polytrimethyleneterephthalate Epoxy resins PS PLA

26

[50] [91] [92, 93] [94] [95] [96] [97] [98]

Mechanical Properties of Polymers Maleic anhydride-g-PP PP EVA PPS Fluoroelastomer Natural rubber, isoprene rubber Filler - silica ABS clay nanocomposites PMMA Ethylene diamine dilaurate and maleic anhydride grafted polypropylene Epoxy resin PS Acrylonitrile Phenylene vinylene copolymers PP PET Filler - talc PP Maleic anhydride-g-PP-jute Filler - minerals PA 6 Filler -montmorillonite clay PE PP PP PLA ABS Ethylene-propylene-diene PVC Epoxy PU PVF Polyimide-amide Miscellaneous reinforcing agents PE - aluminium oxide Epoxy resins - nickel PE- copper PE - barium sulfate PP - barium sulfate PP - jute Styrene butadiene rubber - gold Polyvinyl acetate- caesium bromide Natural rubber composites containing nickel-cobalt-zinc ferrite PLA: Polylactic acid Source: Author’s own iles

[99] [99] [100, 101] [102] [103] [104] [105, 106] [107] [108] [109] [110] [111] [112] [113] [114] [39] [115] [89] [116-120] [121] [122-124] [125, 126] [127] [21] [65] [128, 129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [52] [139] [140]

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2.4 Comparison of the Mechanical Properties of Virgin and Reinforced Plastics

2.4.1 Tensile Strength Table 2.7 shows a comparison of the tensile strengths of a range of engineering polymers with and without glass ibre reinforcement. With the exception of epoxy resins the incorporation of 25−50% of glass ibre, leads to a dramatic increase in tensile strength by a factor, in the case of PTFE, of sevenfold.

Table 2.7 Comparison of tensile strength of virgin unreinforced and glass fibre reinforced engineering polymers Polymers

Unreinforced polymer Tensile strength (MPa) PEEK 92 PAI 185 PET 55 PTFE 25 PA 6 40 PI 72 Epoxy resin 60−80 Source: Author’s own iles

Glass fibre reinforced polymer Glass ibre (%) Tensile strength (MPa) 50 151 195 30 100 25 180 145 40 79 68

Addition of carbon fibre also improves tensile strength especially in PC as shown in Table 2.8. The addition of 30% mineral reduces the tensile strength of polyallylphthalate from 70 MPa to 57 MPa.

Table 2.8 Comparison of the tensile strength of virgin unreinforced and carbon fibre reinforced engineering polymers Polymer Polyacetal

Unreinforced polymer Tensile strength (MPa)

Carbon ibre (%)

Tensile strength (MPa)

73

-

85

30

165

PC 65 Source: Author’s own iles

28

Carbon-fibre reinforced polymer

Mechanical Properties of Polymers The addition of reinforcing agents or illers does not improve tensile strength in all cases as shown in Table 2.7 for glass ibre reinforced epoxy resins. The addition of calcium carbonate also causes a deterioration of tensile strength from 33 MPa for virgin PP to 2.6 MPa in the case of glass illed PP. The addition of minerals also causes a deterioration of the tensile strengths. Aluminium powder and silica both reduce tensile strengths for epoxy resins from 600 to 49 MPa for aluminium and to 72 MPa for silica. Similarly, for polyacetals the addition of silicones reduces the tensile strength from 73 to 55 MPa.

2.4.2 Flexural Modulus The lexural moduli of a range of virgin and glass ibre reinforced engineering polymers are given in Table 2.9

Table 2.9 Comparison of the flexural moduli of virgin and glass fibre reinforced engineering polymers Polymers

Unreinforced polymer Flexural modulus (GPa) PEEK 3.7 PAI 0.6 PET 2.3 PTFE 0.70 PA 6 1 PI 2.40 Epoxy resin 3.0−3.3 Source: Author’s own iles

Glass fibre reinforced polymer Glass ibre (%) Flexural modulus (GPa) 50 10.3 11.1 30 9.5 25 1.03 16 40 132 1.1

It is seen in Table 2.9, that lexural moduli improve considerably upon incorporation of 25 to 50% of glass ibre in the formulation. Epoxy resins are an exception, carbon ibre also improves the lexural modulus of PC from 2.8 to 13 GPa and with polyacetal the addition of carbon ibre improved the lexural modulus from 2.6 to 17.2 MPa. For PP the addition of 20% calcium carbonate produced hardly any change in lexural modulus. No improvement in lexural modulus resulted from the incorporation of minerals, aluminium powder, silica or silicones as shown in Table 2.10.

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Table 2.10 Comparison of flexural modulus of virgin reinforced and reinforced engineering polymers Polymer

Polyacetal Polyallyl phthalate Epoxy resins Epoxy resins Epoxy resins Source: Author’s own iles

Unreinforced Flexural modulus (GPa) Silicone 2.6 Minerals 10.6 80 Aluminium powder 80 Silica 80

Reinforced Flexural modulus (GPa) 2.1 9.5 1.1 9.5 15

2.4.3 Elongation at Break The incorporation at 25−50% of glass ibre into polymers usually produces a dramatic deterioration of the percentage of elongation at break (see Table 2.11).

Table 2.11 Comparisons on elongation at break of virgin in reinforced and glass fibre reinforced engineering polymers Polymer

Unreinforced polymer Elongation at break (%) PEEK 50 PEI 12 PET 300 PTFE 400 PA 6 4 PI 8 Source: Author’s own iles

Glass fibre reinforced polymer Glass ibre (%) Elongation at break (%) 2.2 5 30 22 25 240 3.5 40 1.2

Carbon ibre causes a decrease in elongation at break point from 110 to 2.7% for PC and from 65 to 1% for polyacetal. The addition of minerals or silica to epoxy resins

30

Mechanical Properties of Polymers or polyallylphthalate causes hardly any change in elongation at break, compared to the value obtained for the virgin polymer.

2.4.4 Izod Impact Strength The Izod impact strengths for virgin and glass ibre reinforced engineering polymers are shown in Table 2.12.

Table 2.12 Comparison of Izod impact strength of virgin unreinforced and glass fibre reinforced polymers Polymer

Unreinforced polymer Impact strength (kJ/m) PEEK 0.8 PAI 0.13 PET 0.02 PA 6 0.08 PI 0.08 Source: Author’s own iles

Glass fibre reinforced polymer Glass ibre (%) Impact strength (kJ/m) 0.9 0.10 40 0.24 0.6 40 0.24

The incorporation of carbon ibre produces hardly any change in Izod impact strength of polyacetal (0.04 kJ/m), compared to that of the base polymer (0.06 kJ/m). Various other additives hardly affect Izod impact strength as shown in Table 2.13.

Table 2.13 Comparison of Izod impact strength of virgin unreinforced and reinforced engineering polymers Polymer

PP Polyallyl phthalate Polyacetal Source: Author’s own iles

Impact strength of virgin polymer (kJ/m) Calcium carbonate 0.07 Mineral 0.40 Silicone 0.06

Impact strength of the polymer containing additive (kJ/m) 0.05 0.35 0.085

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Engineering Plastics

2.4.5 Relaxation Behaviour of Polymers The reversible extensibility of a polymer is usually characterised by the measurement of the compression set. Because this measurement is a long-term relaxation experiment, which is usually performed at higher temperature, it summarises the effects of physical and chemical relaxation processes and is therefore not appropriate for the characterisation of the reversible extensibility and the stress relaxation of articles under dynamic service conditions. Wrana and Pask [141] introduced a method for the dynamic characterisation of the reversible extensibility and the stress relaxation. The results of the measurements can be used for a quantitative test of the appropriateness of polymers in articles used dynamically as well as for the determination of the molecular mechanism, which generate the stress relaxation and the permanent deformation in polymers. This method can be used for a quantitative evaluation of polymers in articles used dynamically such as timing belts, engine mounts or seals.

2.5 Mechanical Properties of Particular Polymers More information on the applications of reinforced polymers is available in the next sections.

2.5.1 Polyether Ether Ketone LNP Engineering plastics [65] have introduced a series of formulations based on PEEK reinforced with glass and carbon ibres using PTFE as a lubricant. These polymers have very good impact performance over a wide range of temperatures and have high chemical resistance, good hydrolytic stability and superior resilience. These polymers are targeted at the automotive, business machine, domestic appliance and electronics markets.

2.5.2 Epoxy Resins Fibre-glass reinforced epoxy resins are used particularly in the power transmission, building products and pressure vessel markets. In the case of epoxy resins, tensile strengths fall from 600 in the virgin polymer to 68 MPa while the lexural modulus falls from 3 to 1.1 GPa. A 40% addition of mineral to PA 6,6 is used for automotive under the bonnet applications whilst a 45% addition of mineral and glass ibre to PET is used in

32

Mechanical Properties of Polymers automotive ignition systems. The addition of silica to epoxy resin decreases the tensile strength from 80 to 15 GPa. The in-plane mechanical, viscoelastic and thermal properties of a satin weave carbon fabric impregnated with an amine cured epoxy resin were studied by Abot and co-workers [74]. The in-plane quasi-static behaviour including the failure modes under tension, compression and shear and all the mechanical properties including elastic moduli and strengths were determined. The viscoelastic properties including the glass transition temperature were also measured as well as the coeficients of thermal expansion. These measured properties for the fabric composites were also compared with their corresponding ones for a unidirectional composite with the same ibre and matrix. Loos and co-workers [64] studied the effect of CNT on the mechanical and viscoelastic properties of epoxy matrices. Bisphenol A based epoxy resin nanocomposites were prepared with various small proportions of single-walled carbon nanotubes (SWCNT) and then investigated using acetone as a diluent to reduce the resin viscosity, and the products after removal of the solvent were characterised by FT-IR, Raman spectroscopy, thermogravimetric analysis (TGA), DSC, DMA, tensile, compression, lexural and impact testing, and SEM of the fracture surfaces. The effects of small amounts of SWCNT on mechanical and viscoelastic properties of the nanocomposites are discussed in terms of structural changes in the epoxy matrix. In another study Loos and co-workers [75] fabricated randomly oriented SWCNT/ epoxy resin nanocomposites using tip sonication with solvent and subsequent casting. Two different curing cycles were used to study the effect of the stiffness of the epoxy matrix on the tensile and thermal properties of the composites. The addition of a small amount of SWCNT (0.25 wt%) in rubbery, i.e., soft, matrices, greatly increased Young’s Modulus and the tensile strength of the nanocomposites. The results showed that the tensile properties of the soft epoxy matrices were more inluenced by the addition of carbon nanotubes than stiffer ones. The signiicant improvement in tensile properties was attributed to the excellent mechanical properties and structure of the SWCNT, an adequate dispersion of SWCNT by the tip sonication, and a stronger SWCNT/matrix interfacial adhesion in softer epoxy matrices. A slight improvement in the thermal stability of the nanocomposites was also observed. Epoxy resins are widely used in cryogenic engineering and their cryogenic mechanical properties are important parameters, which have to be improved to meet the high requirements required by cryogenic engineering applications. CNT are regarded as exceptional reinforcements for polymers. However, poor CNT-polymer interfacial bonding leads to unexpected low reinforcing eficiency. Chen and co-workers [77] present a study on the cryogenic mechanical properties of multi-walled carbon

33

Engineering Plastics nanotube (MWCNT) reinforced epoxy nanocomposites, which were prepared by adding MWCNT, to a diglycidyl ether of bisphenol-F epoxy using an ultrasonic technique. When the temperature decreased from room temperature to liquid nitrogen temperature (-196 °C), a strong CNT-epoxy interfacial bonding was observed because of the thermal contraction of epoxy matrix because of the large differences in the thermal expansion coeficients of epoxy and MWCNT, resulting in a higher reinforcing eficiency. Furthermore, synthetic sequences lead to selective dispersion of MWCNT in the brittle primary phase but not in the second phase in the two phase epoxy matrix. Consequently, the cryogenic tensile strength, Young’s Modulus, failure strain and impact strength at -196 °C are all enhanced by the addition of MWCNT at appropriate concentrations. The results suggest that CNT are promising reinforcements for enhancing the cryogenic mechanical properties of epoxy resins that have potential applications in cryogenic engineering areas. Thermoset polymers have been widely used for engineering components, adhesives and as matrixes for ibre-reinforced composites. This is because of their good mechanical properties compared to those of thermoplastic polymers, as thermoset polymers are usually brittle and vulnerable to cracking. Therefore, ductile materials such as micro-sized rubber or Nylon particles are added to thermoset polymers to increase their fracture toughness, which might increase their strength if micro-sized particles act like defects. To improve the fracture toughness of epoxy adhesive, Kim and coworkers [96] mixed nanoparticle additives such as carbon black and nanoclay with epoxy resin. The fracture toughness was measured using the single edge notched bend specimen at room temperature (25 °C) and at a cryogenic temperature (-150 °C). From the experimental results, it was found that reinforcement with nanoparticles improved the fracture toughness at room temperature, but decreased the fracture toughness at the cryogenic temperature in spite of their toughening effect.

2.5.3 Polyethylene Terephthalate The incorporation of 30% glass ibres into PET increases the tensile strength from 55 GPa to 100 MPa and the lexural modulus from 2.3 to 5.9 GPa whilst reducing elongation at break from 300 to 2.2%.

2.5.4 Polydiallylphthalate The introduction of a mineral reinforcing agent into polymer formulations generally causes a deterioration of tensile strength which for polydiallylphthalate containing 30% of mineral reinforcement fell from 70 to 57 GPa.

34

Mechanical Properties of Polymers

2.5.5 Polyamides An appreciable amount of work has been carried out on the use of PA in engineering applications such as automotive parts, precision engineering applications and high strength and stiffness applications such fan blades, gears, bearings and wind turbine blades. Several workers have discussed the mechanical properties of reinforced PA [55]. Keating and co-workers [56] did some research to check whether it was necessary to perform high temperature annealing on semi-crystalline materials and determined its impact on creep strain in glass ibre reinforced polymers, PA 6,6 and PET, which had Tg of 58 and 132 °C, respectively. The improvement after annealing depends on the polymer type, on whether crystallisation during the moulding process is fast or slow and whether the polymer has hydrogen bonded sheets. The physical property changes of these materials observed before and after annealing support the explanation of crystal reorganisation through crystallisation, free volume reduction through densiication and crystal perfection through better chain packing. These data were used to predict long-term creep strains up to 10 years using the time-temperature superposition technique. The accuracy of the prediction is shown with a conidence level of about 90%. Karayannidis and co-workers [55] and Kusmono and co-workers [93] studied crack propagation and impact strength of glass ibre and reinforced PA 6,6 containing up to 12.5% of a functionalised tri-block copolymer styrene-ethylene-butylene-styrene (SEBS), grafted with maleic anhydride (SEBS-g-MA). Blends containing 2.5, 5, 7.5, 10 and 12.5 wt% copolymer were prepared by melt blending in a single screw extruder. Emphasis was placed on mechanical properties in comparison with morphology and thermal properties of the samples. Although the amount of -g-MA added to the PA is not enough to produce a super-tough material, a signiicant increase in the resistance to crack propagation and impact strength was observed in all blends. This behaviour was proportional to the amount of SEBS-g-MA added for samples having up to 10% rubber, while additional amounts seem to have no further effect. A small decrease in tensile strength was observed. It was shown that the extent of grafting of SEBS-g-MA to PA 6,6 is very low. Seldén and co-workers [59] measured weld line tensile strength of injection moulded glass ibre reinforced PA 6 and talc illed PP. Fracture surfaces were also examined using SEM. Lyons [142] obtained creep rupture data and tensile behaviour of glass illed PA and polyphthalamides at temperatures between 23−150 °C. A polyphthalamide with

35

Engineering Plastics 33% glass reinforcement exhibited a good combination of creep resistance, strength and ductility. Sandler and co-workers [69] produced a series of reinforced PA 12, which they strengthened by incorporating MWCNT and carbon nanoibres. The dispersion and resulting mechanical properties for the nanotubes produced by electric arc were compared with those formed by a variety of chemical vapour deposition techniques. A high quality of dispersion was achieved for the nanotubes and the greatest improvements in stiffness were observed using aligned, substrate-grown CNT. Entangled MWCNT led to the largest increase in yield stress. The degrees of polymer and nanoiller alignment and the morphology of the polymer matrix were assessed using x-ray diffraction and DSC. The CNT acted as nucleation sites under slow cooling conditions but no signiicant variations in polymer morphology as a function of nanoscale iller type and loading fraction were observed. A simple rule-of-mixture evaluation of the nanocomposite stiffness revealed a higher effective modulus for the MWCNT compared to the carbon nanoibres because of improved graphitic crystallinity. These workers also compared the effective CNT modulus with those of nanoclays and common short glass and carbon ibre illers in melt blended PA composites. The intrinsic crystalline quality, as well as the straightness of the embedded nanotubes were signiicant factors inluencing the reinforcement capability. In general it was found that the incorporation of an organically modiied clay into a polymer formulation increased the storage modulus, loss modulus and Young’s Modulus but decreased crystallinity. The Tg was improved and the thermal stability tended to improve. Shit [90] studied the effect of annealing temperature on moulded parts of mineral illed PA 6. To avoid the problem of moulded-in stress leading to shrinkage and warpage in a moulded part, products were annealed at a suitable temperature just after processing. It was found that annealing at higher temperatures increased the density of the sample. This was due to the rapid crystallisation of the polymer molecules at higher temperatures, which lead to improvement in all properties except impact strength. The coeficient of thermal expansion decreased with the increase of annealing temperature. The effects of holding pressure, injection velocity, melt temperature and mould temperatures on weld line strength were studied. The effect of changing these parameters on weld line strength was measured and compared with the bulk strength via the weld line factor (deined as strength of a specimen with a weld line against the strength of a specimen without a weld line). The highest weld line factors were obtained for unilled materials moulded using high melt temperature, high holding pressure and low mould temperature.

36

Mechanical Properties of Polymers Gotzmann [60] discusses methods used in the manufacture of metal plastic hybrid components such as glass ibre reinforced PA around a steel or aluminium proile placed in the mould used for injection moulding plastics. Some applications of such components were examined, and computer aided materials selection, inite element analysis and computer simulation systems developed for use in this technology are described. Flightcom developed the Denali headset, which is the irst aviation headset to make almost total use of plastics [143]. Key properties required for the headset included low weight, high impact strength, resistance to extreme heat and cold, and a repeatable, comfortable head-clamping force. Glass reinforced PA was eventually speciied for the headband. The domes or earpieces were moulded from ABS and the microphone housing and elbow was moulded from polyacetal. The earpiece and headset cushions were PU foam covered by vinyl cloth. The incorporation of CNT into polymers can have profound effects on mechanical properties [81, 142, 144, 145] and electrical properties such as conductivity. These properties are retained over a wide range of temperatures [146]. The beneits of incorporating CNT into polymers are reviewed by Mapleston [147]. CNT have been incorporated into a range of polymers to improve their mechanical properties. These include epoxy resins [148] and PA [27]. Tensile properties and hardness were greatly improved. Koo and co-workers [149] compared the beneits of incorporating three different types of nanoparticles on the mechanical properties of PA. The nanoparticles used were montmorillonite clay, surface modiied silica and carbon nanoibre. Licea-Claverie and co-workers [57] studied mechanical stress-strain, impact properties and also thermal properties of PA 6,6 (including some recycled PA) with mixed glass ibre and carbon ibre reinforcements and compared these properties with those of the virgin polymers. No dependence on mechanical properties because of increasing amounts of scrap in the composites was found up to 10.4 wt%. The recycled composites generally showed lower mechanical properties when compared with the virgin composites because of a poor matrix-ibre adhesion. Shen and co-workers [91] used nano-indentation to study the effects of clay concentration on the mechanical properties, such as hardness, elastic modulus and creep behaviour of exfoliated PA 6,6-clay nanocomposites. Results were compared with those obtained by DMA and tensile tests.

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Engineering Plastics

2.5.6 Polystyrene Tanoue and co-workers [97] showed that the storage and loss modulus of organoclayPS composite increased with organoclay content.

2.5.7 Polypropylene Glass ibre illed PP has been the subject of several studies [46-48]. Researchers at Union Carbide [51] reported that the incorporation of 2% of an organosilicone compound into recycled, 38% glass ibre reinforced PP increased the mechanical properties of the recycled sheet with an increase in tensile and lexural strength of 35−40%. Izod impact strength was increased by 30%. Gupta and co-workers [50] studied the Izod impact strength of notched and unnotched PP reinforced with glass ibre, and prepared by a melt blending techniques using chemical coupling. There was considerable improvement in the mechanical and thermal properties in the PP prepared with 1% coupling agent. These properties can be improved further by increasing the amount of glass ibre used. However, impact strength and elongation at break decrease with an increasing amount of glass ibre. Yun-Sheng and co-workers [115] demonstrated that the addition of up to 25% inely divided talc to PP increased tensile and lexural strength to a maximum value. Chaudhary and co-workers [113] showed that the incorporation of silica into PP increased the tensile modulus and strength. The addition of 20% calcium carbonate to PP reduces impact strength from 33 to 2.6 MPa and reduced elongation at break from 150 to 80%. Zhou and co-workers [27] used calcium carbonate as a reinforcing agent for sulfonated PEEK. The calcium carbonate particles were surface treated and the effect of this on the mechanical and thermal properties were determined. The modulus and yield stress of the composites increased with CaCO3 particles loadings. This increase was attributed to the bonding between the particles and the PEEK matrix. DSC experiments showed that the particle content and surface properties inluenced the Tg and the Tm of the composites. The Tg increased with the content of illers while Tm decreased. The treated illers were found to give a better combination of properties, which indicated that the sulfonated PEEK played a constructive role in the calcium carbonate/PEEK composites. Tang and co-workers [150], found that the tensile modulus of propylene-vinyl acetate copolymer increased with an increased iller weight fraction and the impact strength 38

Mechanical Properties of Polymers decreased rapidly when the weight fraction of calcium carbonate fell below 1%. Zhou and co-workers [27] studied the effect of surface treatment of calcium carbonate with sulfonated PEEK on the mechanical properties of the polymer. Tests used included tensile tests, lexural tests, notched Izod impact tests, TGA, DSC and SEM. The modulus and yield stress of the composites increased with CaCO3 particle loading. This increase was attributed to the bonding between the particles and the PEEK matrix, was proved by the SEM of the tensile fracture surface of the composites. The treated illers were found to give a better combination of properties, which indicated that the sulfonated PEEK played a constructive role in the calcium carbonate/PEEK composites. Vincent and co-workers [151] studied the inluence of low on the ibre orientation and mechanical properties in the injection moulding and extrusion of ibre reinforced thermoplastics.

2.5.8 Polyethylene Xiao and co-workers [79] found that the Young’s Modulus and tensile strength of carbon nanoibre reinforced LDPE increased by 89 and 56%, respectively, with incorporation of CNT. Naroozi and co-workers [80] investigated the mechanical properties of mediumdensity polyethylene (MDPE)-MWCNT) nanocomposites reinforced with 0.5−5% of CNT. To clarify the role of both MWCNT content and milling time on the morphology of MDPE, some nanocomposite samples were investigated by using an SEM. To evaluate the role of milling on the microstructure of the nanocomposites, very thin ilms of MDPE/MWCNT were prepared and studied by transmission electron microscopy. Thermal behaviour of these nanocomposites was investigated by using DSC. Standard tensile samples were produced by compression moulding. The dependence of the tensile properties of MDPE on both milling time and MWCNT content was studied by using a tensile test. The results of the microscopic evaluations showed that the milling process could be a suitable method for producing MDPE/ MWCNT nanocomposites. The addition of CNT to MDPE caused a change in its morphology at constant milling parameters. The results of the DSC showed that the crystallisation temperature of MDPE increased as MWCNT were added, although no dependency was observed as milling time increased. The crystallisation index changed from 50−55% as the MWCNT content increased from 0 to 5%. The results of the tensile tests showed that both the Young’s Modulus and the yield strength of MDPE increased as MWCNT were added.

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Engineering Plastics

2.5.9 Ethylene-vinyl Acetate Ardhyananta and co-workers [101] demonstrated the Young’s Modulus of EVA/ organoclay nanocomposites increased as the clay loading was increased up to a value of 92%.

2.5.10 Ethylene Propylene Diene – Polypropylene – Maleic Anhydride Vulcanisates The incorporation of montmorillonite into this polymer increased the elastic modulus when compared to that of the unilled virgin polymer. Barroso-Bujans and co-workers [146] compared the mechanical properties of carbon black-ethylene-propylene-diene terpolymer (EPDM) and CNT-EPDM composites. The introduction of 5 phr CNT into the polymer lead to a slight increase in tensile strength coupled with a marked reduction in strain at break, indicating a decrease in polymer toughness and lexibility. The carbon black had the expected reinforcing effect on the tensile strength of EPDM. However, sulfonated EPDM showed distinct improvements in tensile strength and elongation at break following the introduction of CNT.

2.5.11 Polymethyl Methacrylate It has been found that the Tg of PMMA-silica nanocomposites [152] increased with silica content. Also the thermal properties were enhanced. Thus, the degradation temperature at 10% weight loss was about 30 °C higher than that of pristine PMMA. The results could be due to the ‘trapping effect’.

2.5.12 Fluoropolymers

2.5.12.1 Polyvinylidene Fluoride-clay Nanocomposites In general it was found that increasing the content of organically modiied clays and montmorillonite increased the storage modulus, loss modulus and the Young’s Modulus of polymers and also reduced their crystallinity. The Tg was increased and the thermal stability tended to improve. Clay-PVF composites have a signiicantly improved storage modulus compared to the base polymer over the temperature range 100−150 °C. Various researchers [30, 76, 153] have reported on the mechanised and

40

Mechanical Properties of Polymers thermal behaviour of ibre-glass or glass bead illed PVF-bentonite clay nanocomposites which were shown to have a signiicantly improved storage modulus when compared to the base polymer. The mechanical properties of carbon ibre PVF composites have been studied by Vidhate and co-workers [66]. Shelestova and co-workers [68], studied the effects of modiication of carbon ibres on the thermo-physical properties of carbon illed PTFE.

2.5.12.2 Poly(vinylidene fluoride)-Tetrafluroethylene-Propylene Zhonghai and co-workers [154] studied the mechanical properties of carbon ibre reinforced ilms of this polymer as a function of the degree of crosslinking with triethylenetetramine. In general, an improvement in mechanical properties resulted in little or no effect on the electrical properties of this polymer, which is a strong candidate for the fabrication of lithium battery electrodes.

2.5.13 Natural Rubber and Isoprene Rubber Ramorino and co-workers [104] found that the incorporation of organoclay into these polymers induced considerable mechanical reinforcement with increased stiffness and strength.

2.6 Use of Lubricating Agents in Engineering Polymer Formulations Some engineering polymers contain a variety of lubricating agents such as PTFE, graphite, molybdenum sulide and silicone, which impart to them special properties, see Table 2.14. The uses of lubricants in polymer formulation manufacture, e.g., valve seals, compression rings, piston rings, bearings and so on, is relevant in applications where wear is a consideration. In a particular example the incorporation of 2% silicone into polyacetal improved elongation at break from 0. 5 to 50%.

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Engineering Plastics

Table 2.14 Mechanical applications of lubricated engineering polymers (concentration of lubricating agent in brackets) Polymer

Application Lubricant - graphite Polyimides (20%) Valve seals, compression rings and bearings PAI Washers, piston rings, seals and impellers PTFE (15−25%) Rings and bearings Lubricant - PTFE Polyoxymethylene (polyacetals) Bearings, gears and bushes PA 6,12 (20%) Gears PI Piston rings, machine tools, bearings and valve discs Polyphenylene sulide (20%) Anti-friction gears, bolts and screws Lubricant - silicone Polyoxymethylene (20%) (polyacetal) Gears, bearings and bushes Polybutylene terephthalate (2%) Gears, cogs and cams PA 6,6 (2%) Bushes and valve seals Lubricant - molybdenum disulfide PA 6 Housing and cams PA 6,6 Bearings, valves, seals and cams PI Machine bearings, insulations, bushes and drive rollers Source: Author’s own iles

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43

Engineering Plastics 23. T. Sakurai, T. Matsuoko, S. Koda and H. Nomura, Journal of Applied Polymer Science, 2000, 76, 6, 978. 24. K. Hausmann, B. Rioux and C.Y. Lee, Plastiques et Elastomers Magazine, 2003, 54, 3, 14. 25. K. Hausmann, R. Chou and B. Rioux in Proceedings of the Rapra Addcon World Conference 2002, Budapest, Hungary, 2002, Paper No.280, p.279. 26. M. Yuan, J. Galloway, R. Hoffman and S. Bhatt in Proceedings of the 66th SPE ANTEC Conference, Milwakee, WI, USA, 2008, p.1567. 27. B. Zhou, X. Ji, Y. Sheng, L. Wang and Z. Jiang, European Polymer Journal, 2004, 40, 10, 2357. 28. J.D.D. Melo and D.W. Radford, Journal of Reinforced Plastics and Composites, 2005, 24, 5, 545. 29. M. Koh, B. Larin, J. Mackey and F. Tofan in Proceedings of the SPE GPEC Conference: Plastics Impact on the Environment, Detroit, MI, USA, 2002, Paper No.5. 30. H. Fan, Y. Gu and M. Xie, Journal of Polymer Science, Part A: Polymer Chemistry Edition, 2003, 41, 4, 554. 31. M. Siddiq and C. Wu, Journal of Applied Polymer Science, 2001, 81, 7, 1670. 32. G. Abraham, S. Packirisamy, S.S. Bhagawan, G. Balasubramanian and R.I. Ramaswamy, Journal of Materials Science, 2007, 42, 19, 8342. 33. J.P. Habas, J. Peyrelasse and M.F. Grenier-Loustalot, High Performance Polymers, 1996, 8, 4, 515. 34. S.I. Matsuda and S. Ando, Kobunshi Ronbunshu, 2004, 61, 1, 29. 35. Plastics Engineering, 2003, 59, 3, 8. 36. Y-W. Park, D-S. Lee and S-H. Kim, Journal of Applied Polymer Science, 2004, 91, 3, 1774. 37. F.P. La Mantia, Macplas, 2000, 25, 223, 35. 38. S.C. Tjong and Y.Z. Meng, Polymer, 1997, 38, 18, 4609.

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Mechanical Properties of Polymers 39. K. Tajima, T. Kanamoto and M. Itoh, Kobunshi Ronbunshu, 2004, 61, 6, 346. 40. P.J. Bates, C. Dyck and M. Osti, Polymer Engineering and Science, 2004, 44, 4, 760. 41. M. Gröning and M. Hakkarainen, Journal of Applied Polymer Science, 2002, 86, 13, 3396. 42. Y-T. Chern, H-C. Shiue and S.C. Kao, Journal of Polymer Science, Part A: Polymer Chemistry Edition, 1998, 36, 5, 785. 43. D. Leblanc and L.C. Sederel, Kunststoffe German Plastics, 1992, 82, 9, 31. 44. British Plastics and Rubbers, 2004, April, 10. 45. J. Van Ruiten, R. Riedel, R. Deblieck, R. Bronwer and J.P. Pennine, Journal of Materials Science, 2001, 36, 13, 3119. 46. M. Jakleweiz, A. Litak and M. Ostoja-Starzewski, Journal of Applied Polymer Science, 2004, 91, 6, 3866. 47. M-F. Lin, Y-C. Shu and J-L. Guo in Proceedings of the IUPAC Polymer Symposium: Functional and High Performance Polymers, Taipei, Taiwan, 1994, p.549. 48. M. Modesti and A. Lorenzetti, European Polymer Journal, 2003, 39, 2, 263. 49. Plastics Technology, 2003, 49, 8, 29. 50. A.P Gupta, U.K. Saroop, G.S. Jha and M. Verma, Polymer-Plastics Technology and Engineering, 2003, 42, 2, 297. 51. Reuse/Recycle, 1993, 23, 2, 12. 52. S. Mishra and N.G. Shimpi, Journal of Applied Polymer Science, 2007, 104, 3, 2018. 53. L. Huang, Q. Yuan, W. Jiang, L. An, S. Jiang and R.K.Y. Li, Journal of Applied Polymer Science, 2004, 94, 5, 1885. 54. P. J. Farrington and R.G. Speight in Proceedings of the 63rd SPE ANTEC Conference, Boston, MA, USA, 2005.

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Engineering Plastics 55. G.P. Karayannidis, D.N. Bikiaris, G.Z. Papageorgiou and V. Bakirtzis, Advances in Polymer Technology, 2002, 21, 3, 153. 56. M.Y. Keating, L.B. Malone and W.D. Saunders, Journal of Thermal Analysis and Calorimetry, 2002, 69, 1, 37. 57. A. Licea-Claverie, F.J.U. Carrillo, A. Alvarez-Castillo and V.M. Castaño, Polymer Composites, 1999, 20, 2, 314. 58. E. Klata, S. Borysiak, K. Van der Velde, J. Garbarczyk and J. Krucińska, Fibres and Textiles in Eastern Europe, 2004, 12, 3, 64. 59. R. Seldén, Polymer Engineering and Science, 1997, 37, 1, 205. 60. G. Gotzmann, Revue Generale des Caoutchoucs et Plastiques, 1996, 748, 37. 61. P.A. Toensmeier, Modern Plastics International, 2001, 31, 5, 108. 62. F.H. Gojny, M.M.G. Wichmann, B. Fiedler, W. Banhofer and K. Schulte, Composites Part A: Applied Science and Manufacturing, 2005, 36, 11, 1525. 63. Y. Nishitani, I. Sekiguchi, B. Hausnerova, N. Zdrazilova and T. Kitano, Polymers and Polymer Composites, 2007, 15, 2, 111. 64. M.R. Loos, L.A.F. Coelho, S.H. Pezzin and S.C. Amico, Materials Research, 2008, 11, 3, 347. 65. Plastics and Rubbers Weekly, 1997, 1698, 13. 66. S. Vidhate, E. Ogunsona, J. Chung and N.A. D’Souza in Proceedings of the 66th SPE ANTEC Conference, Milwaukee, WI, USA, 2008, p.74. 67. C-H. Chen and K-C. Lien, Polymers and Polymer Composites, 2006, 14, 2, 155. 68. V.A. Shelestova, O.R. Yurkevich and P.N. Grakovich, Polymer Science Series B, 2002, 44, 3-4, 94. 69. J.K.W. Sandler, S. Pegel, M. Cadek, F. Gojny, M. van Es, J. Lohman, W.J. Blau, K. Schulte, A.H. Windle and M.S.P. Shaffer, Polymer, 2004, 45, 6, 2001. 70. B. Wang, G. Sun, X. He and J. Lin, Polymer Engineering and Science, 2007, 47, 10, 1610.

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Mechanical Properties of Polymers 71. V.E. Yudin, V.M. Svetlichnyi, A.N. Shumakov, D.G. Letenko, A.Y. Feldman and G. Marom, Macromolecular Rapid Communications, 2005, 26, 11, 885. 72. S-M. Yuen, C-C.M. Ma, C-C. Teng, H-H. Wu, H-C. Kuan and C-L. Chang, Journal of Polymer Science, Part B: Polymer Physics Edition, 2008, 46, 5, 472. 73. D. Wu, L. Wu, Y. Sun and M. Zhang, Journal of Polymer Science, Part B: Polymer Physics Edition, 2007, 45, 23, 3137. 74. J.L. Abot, A. Yasmin, A.J. Jacobsen and I.M. Daniel, Composites Science and Technology, 2004, 64, 2, 263. 75. M.R. Loos, S.H. Pezzin, S.C. Amico, C.P. Bergman and L.A.F. Coelho, Journal of Materials Science, 2008, 43, 18, 6064. 76. Q. Yuan, W. Jiang, L. An and R.K.Y. Li, Polymers for Advanced Technologies, 2004, 15, 7, 409. 77. Z-K. Chen, J-P. Yang, Q-Q. Ni, S-Y. Fu and Y-G. Huang, Polymer, 2009, 50, 19, 4753. 78. Y.S. Song, Polymer Engineering and Science, 2006, 46, 10, 1350. 79. K.Q. Xiao, L.C. Zhang and I. Zarudi, Composites Science and Technology, 2007, 67, 2, 177. 80. M. Naroozi and S. Zebarjad, Journal of Vinyl and Additive Technology, 2010, 16, 2, 147. 81. B. Hausnerova, N. Zdhrazilova, T. Kitano and P. Saha, Polymeri, 2006, 51, 1, 33. 82. H-C. Kuan, C-C.M. Ma, W-P. Chang, S-M. Yuen, H-H. Wu and T-M. Lee, Composites Science and Technology, 2005, 65, 11-12, 1703. 83. S. Peeterbroeck, M. Alexandre, J. B. Nagy, N. Moreau, A. Destrée, F. Monteverde, A. Rulmont, R. Jérôme and P. Dubois, Macromolecular Symposia, 2005, 221, 115. 84. M. Lai, J. Li, J. Yang, J. Liu, X. Tong and H. Cheng, Polymer International, 2004, 53, 10, 1479.

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Engineering Plastics 85. S.H. Joo, C. Pak, E.A. Kim, Y.H. Lee, H. Chang, D. Seung, Y.S. Choi, J-B. Park and T.K. Kim, Journal of Power Sources, 2008, 180, 1, 63. 86. X. Xu, Y. Song, Q. Zheng and G. Hu, Journal of Applied Polymer Science, 2007, 103, 3, 2027. 87. Y.W. Leong, Z.A.M. Ishak and A. Arifin, Journal of Applied Polymer Science, 2004, 91, 5, 3327. 88. J-Z. Liang, Journal of Applied Polymer Science, 2007, 104, 3, 1692. 89. M. Oksuz and H. Yildirim, Journal of Applied Polymer Science, 2005, 96, 4, 1126. 90. S.C. Shit, Popular Plastics and Packaging, 2002, 47, 11, 81. 91. L. Shen, I.Y. Phang, L. Chen, T. Liu and K. Zeng, Polymer, 2004, 45, 10, 3341. 92. T. Liu, W.C. Tjiu, C. He, S.S. Na and T-S. Chung, Polymer International, 2004, 53, 4, 392. 93. Z.A. Kusmono, W.S. Mohdishak, T. Chow, T. Takeichi and Rochmadi, European Polymer Journal, 2008, 44, 4, 1023. 94. C.Y. Lew, W.R. Murphy and G.M. McNally in Proceedings of the 62nd SPE ANTEC Conference, Chicago, IL, USA, 2004, p.304. 95. Z. Liu, K. Chen and D. Yan, Polymer Testing, 2004, 23, 3, 323. 96. B.C. Kim, S.W. Park and D.G. Lee, Composite Structures, 2008, 86, 1-3, 69. 97. S. Tanoue, L.A. Utracki, A. Garcie-Rejon, P. Sammut, M-T. Ton-That, I. Pesneau, M.R. Kamal and J. Lyngaae-Jørgensen, Polymer Engineering and Science, 2004, 44, 6, 1061. 98. Y. Di, S. Iannace, E. Di Maio and L. Nicolais, Journal of Polymer Science, Part B: Polymer Physics Edition, 2005, 43, 6, 689. 99. H. Mirzazedeh A.A. Katbab and S. Bazgir in Proceedings of the 8th International Symposia on Polymers for Advanced Technologies Conference, Budapest, Hungary, 2005, Paper No.4. 100. E. Nazockdast, H. Nazockdast and F. Goharpey, Polymer Engineering and Science, 2008, 48, 7, 1240. 48

Mechanical Properties of Polymers 101. H. Ardhyananta, H. Ismail and T. Takeichi, Journal of Reinforced Plastics and Composites, 2007, 26, 8, 789. 102. L.N. Song, M. Xiao, D. Shu, S.J. Wang and Y.Z. Meng, Journal of Materials Science, 2007, 42, 4, 1156. 103. M.A. Kader, M-Y. Lyu and C. Nah, Composites Science and Technology, 2006, 66, 10, 1431. 104. G. Ramorino, F. Bignotti and R. DeSantis and T. Ricco in Proceedings of the IOM Conference – Elastomers for Engineering: Future Trends, London, UK, 2006, p.36. 105. K. Zheng, L. Chen, Y. Li and P. Cui, Polymer Engineering and Science, 2004, 44, 6, 1077. 106. Y. Hsing Hu, C-Y. Chen and C-C. Wang, Macromolecules, 2004, 17, 2411. 107. H. Ardhyananta, H. Ismail and T. Takeichi, Journal of Reinforced Plastics and Composites, 2002, 26, 8, 789. 108. G.A. Suryadiansyah, H. Ismail and B. Azhari, Polymer Composites, 2008, 29, 10, 1169. 109. V. Pascual-Sánchez and J.M. Martin-Martínez, Macromolecular Symposia, 2006, 233, 137. 110. C. Bartholme, E. Beyou, E. Bourgeat-Lami, P. Cassagnau, P. Chaumont, L. David and N. Zydowicz, Polymer, 2005, 46, 23, 9965. 111. O. Ruzimuradov, G. Rajan and J. Mark, Macromolecular Symposia, 2006, 245-246, 322. 112. T.P. Nguyen, S.H. Yang, J. Gomes and M.S. Wong, Synthetic Metals, 2005, 151, 3, 269. 113. D.S. Chaudhary, M.C. Jollands and F. Cser, Polymers and Polymer Composites, 2004, 12, 5, 383. 114. D.W. Chae and B.C. Kim, Journal of Materials Science, 2007, 42, 4, 1238. 115. D. Yun-Sheng, G. Hong-Wei and W. Seng-Shen, Polymer Materials Science and Engineering, 2005, 21, 5, 90.

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Engineering Plastics 116. K. Stoefler, P.G. Laleur and J. Denault, Polymer Engineering and Science, 2008, 48, 8, 1449. 117. Y.C. Kim, S.J. Lee, J.C. Kim and H. Cho, Polymer Journal (Japan), 2005, 37, 3, 206. 118. K. Stoefler, P.G. LaFleur and J. Denault in Proceedings of the 64th SPE ANTEC Annual Conference, Charlotte, NC, USA, 2006, p.263. 119. S.M. Lomakin, L.A. Novokshonova, P.N. Brevnov and A.N. Shchegolikhin, Journal of Materials Science, 2008, 43, 4, 1340. 120. Y-S. Ding and Z-C. Zhang, Polymer Materials Science and Engineering, 2005, 21, 4, 256. 121. W. Shao, Q. Wang and H. Ma, Polymer International, 2005, 54, 2, 336. 122. D-R. Yei, S-W. Kuo, Y-C. Su and F-C. Chang, Polymer, 2004, 45, 8, 2633. 123. B-Q. Zhang, G-D. Chen, C-Y. Pan, B. Luan and C-Y. Hong, Journal of Applied Polymer Science, 2006, 102, 2, 1950. 124. D-R. Yei, S-W. Kuo, H-K. Fu and F-C. Chang, Polymer, 2005, 46, 3, 741. 125. C.W. Shyang and L.S. Kuen, Polymers and Polymer Composites, 2008, 16, 4, 263. 126. E. Lezak, Z. Kulinski, R. Masirek, E. Piorkowska, M. Pracella and K. Gadzinowzka, Macromolecular Bioscience, 2008, 8, 12, 1190. 127. B. Pourabbas and N. Azimi, Journal of Composite Materials, 2008, 42, 23, 2499. 128. F. Gong, M. Feng, C. Zhao, S. Zhan and M. Yang, Polymer Degradation and Stability, 2004, 84, 2, 289. 129. Y. Deng, A. Gu and Z. Fang, Polymer International, 2004, 53, 1, 85. 130. H-T. Lee and L-H. Lin, Macromolecules, 2006, 39, 18, 6133. 131. Y-P. Wang, X-H. Gao, R-M. Wang, H-G. Liu, C. Yang and Y-B. Xiong, Reactive and Functional Polymers, 2008, 68, 7, 1170. 132. T. Mikolajczyk and M. Olejnik, Fibres and Textiles in Eastern Europe, 2007, 15, 2, 26.

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Mechanical Properties of Polymers 133. B. Mary, C. Dubois, P. J. Carreau and P. Brousseau, Rheologica Acta, 2006, 45, 5, 561. 134. J. Burghardt, N. Hansen, L. Hansen and G. Hansen in Proceedings of the SAMPE 06 Conference: Creating New Opportunities for the World Economy, Volume 51, Long Beach, CA, USA, 2006, Paper No.131. 135. A.S. Luyt, J.A. Molei and H. Krump, Polymer Degradation and Stability, 2006, 91, 7, 1629. 136. F. Bianchi, A. Lazzeri, M. Pracella, A. D’Aquino and G. Ligeri, Macromolecular Symposia, 2004, 218, 191. 137. K. Wang, J. Wu and H. Zeng, Polymers and Polymer Composites, 2006, 14, 5, 473. 138. S. Mohanty, S.K. Nayak, S.K. Verma and S.S. Tripathy, Journal of Reinforced Plastics and Composites, 2004, 23, 6, 625. 139. M. Abdelaziz, Journal of Applied Polymer Science, 2004, 94, 5, 2178. 140. D. Puryanti, S.H. Ahmad, M.H. Abdullah and A.N.H. Yusoff, International Journal of Polymeric Materials, 2007, 56, 3, 327. 141. C. Wrana and S. Pask, Rubber and Plastics News, 2007, 36, 17, 18. 142. J.S. Lyons, Polymer Testing, 1998, 17, 4, 237. 143. P.A. Toensmeier, Modern Plastics International, 2001, 31, 5, 108. 144. L. Reade, Asian Plastics News, 2001, January/February, 24. 145. L. Priya and J.P. Jog, Journal of Polymer Science: Polymer Plastics Edition, 2003, 41, 1, 31. 146. F. Barroso-Bujans, M. Arroyo, E. San Juan, I. Rodriguez-Ramos, M. Perez-Cabero, E. Rjande and M.A. Lopez-Manchado in Proceedings of the IOM Conference – Elastomers for Engineering: Future Trends, London, UK, 2006, p.30. 147. P. Mapleston, Modern Plastics International, 2002, 32, 7, 52. 148. A.T. Johnson, High Performance Plastics, 2002, June, 10.

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Engineering Plastics 149. J.H. Koo, S. Lao, W. Ho, K. Ngyuen, J. Cheng, and L. Pilato in Proceedings of the SAMPE Fall Technical Conference: Global Advances in Materials and Process Engineering, Volume 38, Dallas, TX, USA, Paper No.32. 150. C.Y. Tang, L.C. Chan, J.Z. Hiang, K.W.E. Cheng and T.L. Wong, Journal Reinforced Plastics and Composites, 2002, 21, 15, 1337. 151. M. Vincent, Composites Plastique Renforces Fibres de Verre Textile, 1997, No.22, July/August, 44. 152. C.Y. Lai, S.M. Sapuan, M. Ahmad, N. Yahya and K.Z.H.M. Dahlan, Polymer-Plastics Technology and Engineering, 2005, 44, 4, 619. 153. W.S. Chow and Z.A.M. Ishak, Express Polymer Letters, 2007, 1, 2, 77. 154. C. Zhonghai, L. Christiansen and T.T. Dahn, Journal of Applied Polymer Science, 2004, 91, 2949.

52

3

Thermal Properties of Polymers

3.1 Introduction Applications of polymers, which rely on good thermal properties are listed in Table 3.1. Important thermal properties of polymers are shown in Table 3.2.

Table 3.1 Thermal applications of polymers (in brackets - % glass-fibre reinforcement where applicable) Crosslinked PE PP (20%) Alkyd resins (30%) PPO PEEK (2%) PBT PBT (45% mineral and glass ibre) PA 11 (30%) PA 12 (30%) PEI PEI (10−20%) PEI (30%) PPS (30% carbon ibre) PPS (40% glass ibres) Perluoroalkoxyethylene PVDF PA: Polyamide PBT: Polybutylene terephthalate PE: Polyethylene PEEK: Polyether ether ketone PEI: Polyether-imide PP: Polypropylene PPO: Polyphenylene oxide PPS: Polyphenylenesulide PVDF: Polyvinylidene luoride Source: Author’s own iles

Heat resistant housings and heat shrinkable tubing Cooling systems and expansion tanks Microwave ovens Components for heating systems High temperature applications Heat resistant panels Heating appliances and oven grills Heat resistant components Heat resistant housings Microwave oven parts, high temperature switchgear High temperature connectors and heat exchangers Thermal protectors High heat applications High heat resistant applications Heater cables Heat shrinkable tubing

53

54

GP

GP

GP

GP

Mineral illed

GP

GP

GP

GP

PEEK

Polydiallyl isophthalate

Polydiallyl phthalate

Polyarylates

Alkyl resins

PC

PPO

PMMA

EVA copolymer

Glass ibre reinforced

GP

GP

Epoxy resins

PET

GP

Ethylene-propylene copolymer

GP

GP

Polymethyl pentene

GP

2% calcium carbonate illed

PP

PBT

2

GP

HDPE

Acetal

0.05

GP

Crosslinked PE

18

6

6

12

3.75

6.3

3

3

4.8

8

12

11

18

12

6

20

20

20

GP

LDPE

2

-

0.6

-

0.4

2.5

0.3

2

1.2

0.4

2

1.8

0.5

-

0.25

2.5

1.2

3

3

3

20

103

137

150

>260

171

>260

>260

>260

72

150

160

>260

>260

93

100

105

45

60

50

Heat distortion temperature at 0.45 MPa (°C)

20

90

129

60

220

170

210

280

160

70

60

110

200

230

54

41

68

37

60

35

Very good

Good

Poor

Good

Poor

-

Good

Good

Very good

Very poor

Poor

Good

Very poor

Very poor

Poor

Very poor

Very poor

Very good

Good

Very good

160−220

-

250−300

-

40-80

-

60−90

60−90

350−390

260−280

230−270

190−210

60−80

N/R

310−350

260−320

240−290

220−260

150−170

220−260

20−40

-

30−110

-

150−180

-

150−180

150−180

120−160

20−30

30−90

60−120

160−190

N/R

100−150

40−70

30−50

20−60

20−80

20−40

Heat Brittle Melt Mould distortion temperature temperature temperature temperature (°C) (°C) (°C) at 1.80 MPa (°C)

Table 3.2 Thermal properties of polymers Expansion Mould coefficient shrinkage (m/m/°C (%) × 10-5)

Grade

Polymer

50

70

80

120

130

130

160

180

250

60

120

90

130

130

60

75

100

50

90

50

Maximum operating temperature (°C)

-

-

200

-

-

-

180

180

250

-

120

-

-

170

-

-

-

-

-

-

Continuous use temperature (°C)

Engineering Plastics

GP

GP

GP

GP

GP

GP

GP

Thermoplastic 15 elastomer

GP

GP

PA 6

PA 11

PA 12

PA 6,12

PAI

PI

PEI

PU

PTFE

PVF

8

Glass ibre reinforced

PA 6,10

16

20

5

GP

EthyleneGP chlorotriluoroethylene copolymer

GP

30% carbon ibre reinforced

GP

GP

GP

Ethylenetetraluoroethyelene copolymer

Fluorinated ethylenepropylene copolymer

PPS

PSU

PES

Silicones

16

Perluorooxyethylene

6

5.5

5.5

2.8

21

GP

GP

PVDF

9

15

6.2

1.5

3.6

9

11

9

10

3

GP

PA 6,6

1.5

2

0.6

0.7

0.3

2.5

3

3

4

3

-

-

1.5

0.6

01

0.7

1.1

1.5

1

1.2

0.4

200

>260

>260

179

>260

70

115

105

74

121

121

121

20

210

>260

>260

160

150

150

250

220

100

300

203

174

244

50

76

71

30

82

82

54

20

200

360

274

80

55

55

80

210

Poor

Very good

Good

Good

Good

Very good

Good

Excellent

Good

Poor

Good

Excellent

Very good

Good

Good

Good

Very good

Good

Very good

Very good

Very good

200

60−80

320−380

310−390

315−360

340−360

270−300

310−350

74

280−320

-

-

195−230

340−420

-

315−360

160

190−210

200−280

230−280

250−280

100

180−200

90−160

90−160

40−140

50−200

90-100

50−200

30

80−90

-

-

20−55

70−170

-

180−220

80

90−60

40−60

40−60

60−100

80

240

180

150

200

150

130

160

170

130

150

180

70

170

360

210

70

70

70

80

70

-

-

180

-

190

-

-

180

-

-

-

-

-

170

-

-

-

-

-

-

Thermal Properties of Polymers

55

56

Source: Author’s own iles

PVF: Polyvinyl luoride

PU: Polyurethane

PTFE: Polytetraluoroethylene

PSU: Polysulfone

PP: Polypropylene

PMMA: Polymethyl methacrylate

PI: Polyimide

PET: Polyethylene terephthalate

PES: Polyether sulfone

PC: Polycarbonate

PAI: Polyamide imide

N/R: Not reported

LDPE Low-density polyethylene

GP: General purpose.

HDPE: High-density polyethylene

EVA: Ethylene-vinyl acetate

Engineering Plastics

Thermal Properties of Polymers

3.2 Thermal Expansion Coefficient This property can range from as low as 0.5 mm/°C × 10-5 in epoxy resins to as high as 20 mm/°C × 10-5 in low-density polyethylene (LDPE) or HDPE or some luorinated polymers. Not surprisingly, a high linear coeficient expansion is associated with high percentage mould shrinkage and conversely, polymers with a low coeficient of expansion have a low percentage shrinkage in the mould. Thermomechanical analysis (TMA) is the measurement of dimensional changes (such as expansion, contraction, lexure, extension, and calorimetric expansion and contraction) in a material. It is measured by the movement of a probe which is in contact with the sample in order to determine temperature-related mechanical behaviour in the temperature range of 180−800 °C. This occurs as the sample is heated, cooled (temperature plot), or held at a constant temperature (time plot). It also measures linear or volumetric changes in the dimensions of a sample as a function of time and force. TMA has been reviewed by many researchers including Riga [1] and Cebe and coworkers [2]. Subobh and co-workers [3] observed that the incorporation of ceramic powder iller into PTFE composites had no effect on polymer melting point but as the iller level increased the coeficient of thermal expansion reduced whilst the thermal conductivity increased. Sham and Kim [4] investigated the evolution of residual stresses during curing and thermal cycling of various epoxy resins by means of bi-material strip bending experiments within the chamber of dynamic mechanical test equipment. The resins tested were a neat epoxy resin, a silica-modiied underill epoxy resin and a rubbermodiied no-low underill epoxy resin. Changes in the viscosity and kinetics of curing of the resins with temperature were followed and related to residual stress evolution. The thermal expansion coeficients of the resins were determined using a constitutive equation relating residual stress to changes in elastic modulus with temperature and compared with those obtained from TMA. As the demand for smaller, more-sophisticated electronic telecommunications, automotive parts, appliances and lighting products has increased [5], so has the power density requirements needed to run them. To control heat build-up in such devices, designers commonly use ceramics, and metals such as aluminium, to draw heat away from the components. However, these materials add weight and limit design freedom. Conventional plastics, although lightweight and easily moulded, are good thermal insulators and, therefore, poor conductors. Thus, conventional plastic components overheat, often developing localised ‘hot spots’ as they cannot dissipate or spread heat effectively. These hot spots degrade the mechanical performance and

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Engineering Plastics the part may eventually fail. The recent development of thermally conductive plastics now allows designers to specify injection mouldable polymers that carry the same heat transfer capacity as metals and ceramics. Through part consolidation and more design freedom, these injection mouldable resins often produce parts that are half the weight of their aluminium counterparts. Thermally conductive plastics also have good chemical resistance and give up heat faster during moulding than conventional plastic, which decreases cycle times from 20 to 50%. An inherently low coeficient of thermal expansion boosts dimensional stability and lowers shrinkage rates. This allows the use of plastics to replace metals and ceramics in dimensionally critical parts for micro-electronic, optical, mechanical and medical applications. Fan and co-workers [6] found that a liquid crystalline PI prepared by copolycondensation of 3,5-diamino-benzoic-4ʹ-biphenyl ester, 4,4ʹ-diamino-biphenyl ether and 3,3ʹ,4,4ʹoxydiphthalic dianhydride film had a 40% decrease in expansion coefficient accompanying a 270% improvement in tensile strength and a 300% improvement in modulus. These factors give a polymer with good ilm processibility.

3.3 Mould Shrinkage This is the inherent shrinkage of a material during injection moulding. Moulding conditions, orientation of illers, orientation of low and other factors can all inluence the speciic level of immediate shrinkage but the inherent quality is material dependent. Crystallisation occurring after moulding inluences ‘dimensional stability’. The apparatus for the measurement of this property is described in DIN 53464 [7]. Bertacchi and co-workers [8] have reported computer-simulated mould shrinkage studies on talc-illed PP, glass-reinforced PA and a PC/acrylonitrile-butadiene-styrene (ABS) blend. It is seen from Table 3.2 that the shrinkage occurring during the moulding of polymers can range from as low as less than 1% for an ethylene-propylene copolymer, epoxy resins, polydimethyl phthalate, PPO, alkyl resins, PSU and PES, all of which do not cause much dificulty in the case of shrinkage values as high as 1.5%. These include PA 6,6 and PA 12. Polyarylates, polymethylpentene, alkyd resins and luorinated ethylene-propylene copolymers all have higher values of shrinkage and this can cause problems during polymer moulding. Kumar and Shit [9] point out that crystalline plastic materials such as PA, which are used to make many engineering components, suffer problems due to shrinkage. The shrinkage occurs because of the crystallisation of the polymer as it becomes solid

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Thermal Properties of Polymers from the liquid state in the mould. The extent of shrinkage of plastics processed by injection moulding is affected by many factors such as cylinder temperature, injection pressure, cooling time, hold time, and so on. Since crystalline material has an ordered structure, it occupies less volume. The decline in volume is indicative of the onset and degree of crystallisation. Since this varies with moulding conditions, it is usually more dificult to maintain uniform dimensional tolerances in the moulded part of a highly crystalline material. The moulding conditions also affect the other properties of the plastics material. Thus, optimisation of these moulding conditions for achieving minimum shrinkage without sacriicing the other properties of PA 6,6 is important.

3.4 Melting Temperature or Softening Point The Vicat method measures the temperature at which an arbitrary determination or a speciied needle penetration (Vicat) occurs when polymers are subjected to a standardised set of testing conditions. This property can also be measured by using TMA [plots of temperature versus compression (mm)]. Tang and co-workers [10] found that the Vicat softening temperature (Ts) of ABScalcium carbonate composites increased with the addition of iller which indicated the beneicial effect of the iller on the heat resistance of the terpolymer. A ring apparatus has been used to determine a suitable temperature range for the extrusion of LDPE/HDPE, LDPE/PP, HDPE/PP blends [11] and PPS-acrylonitrilebutadiene blends. The melting temperature (Tm) is deined as the temperature at which crystalline regions in a polymer melt. In semi-crystalline polymers, some of the macromolecules are arranged in crystalline regions, known as crystallites, whilst the matrix is amorphous. The greater the concentration of crystallites, the greater the crystallinity and the more rigid the polymer is, i.e., the higher the Tm value. The true melting points of crystalline polymers can be determined by plotting the differential scanning calorimetry (DSC) melting peak temperatures as a function of the square root of heating rate and linear extrapolations to zero heating rate. Differential thermal analysis (DTA) has been used to study the effect of side-chain lengthin polymers on the melting point and the effect of heating rate of polymers on their melting point. DSC has been used to evaluate multiple peaks in polymers [12, 13]. DSC has also been used to study the heat changes occurring in a polymer as it is cooled (plots of temperatures versus heat low).

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Engineering Plastics TMA has been used for determining softening in polymers by measuring the degree of probe penetration into a polymer at particular applied forces as a function of temperature. This technique allows determination of Tm and the evaluation of dimensional properties over the temperature range of use or under actual accelerated condition cycles (plots of temperature versus compression). Some engineering polymers with particularly high Ts are shown in Table 3.3, which also shows the maximum operating temperature recommended by the manufacturers of these polymers.

Table 3.3 Polymers with particularly high softening or Tm Polymers PEEK PAI PEI Ethylene-polytetraluoroethylene Fluorinated ethylene propylene PPS PSU PES PI

Tm (°C) 350−390 315−360 340−420 310−350 340−360 315−360 310−390 320−380 -

Maximum operating temperature (°C) 250 210 170 160 150 200 150 180 360

Source: Author’s own iles

3.4.1 Polyaryl Ether Ketone This polymer is used widely in engineering applications. Understanding its thermal and rheological behaviour is critical to predicting its moulding processability, post process properties and structural behaviour and properties. Such studies focus on the inluence of molecular weight on thermal and rheological properties of polyaryl ether ketones. Yuan and co-workers [14] used DSC, dynamic mechanical thermal analysis and capillary rheometry to compare Tm, crystallinites, crystallisation temperature and rheological properties of polyaryl ether ketones with different molecular weights.

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Thermal Properties of Polymers

3.4.2 Polyester Amide Tetsuka and co-workers [15] showed that the Tm of copolymers prepared by twostep polycondensation reactions of adipate, butane-1,4-diamine and linear diol homopolyesters were higher than those of polyesters consisting of the same ester units, and tended to increase with an increase in amide content of copolymers produced from adipate, butane-1,4-diol, and butane-1,4-diamine had especially high thermal stabilities compared to polytetramethylene adipate. They had Tm of more than 200 °C.

3.4.3 Polyimides and Polyamides Hsiao and co-workers [16, 17] compared glass transition temperatures (Tg) and Ts for PI [16] and luorinated PI [17]. These polymers had Tg in the range of 253−325 °C (measured by DSC) and Ts in the range of 250−300 °C (measured by TMA). Decomposition temperatures for 5% weight loss all occur above 500 °C in both air and nitrogen atmospheres. The dielectric constants of these polymers ranged from 3.17−3.64 at 1 MHz. The properties of these luorinated PI were also compared with those of PI. These PI showed Tg between 190−255 °C, depending on the diamine used in their manufacture. They also showed decomposition temperatures for 10% weight loss were above 420 °C.

3.5 Maximum Operating Temperature Maximum temperatures are based on the Underwriters Laboratories (UL) rating for the long-term (100,000 h) ability for a material to sustain mechanical, electrical and impact loads. Speciically the UL temperature is deined as that temperature which causes the tensile strength of the material to fall to half its initial value after exposure of 100,000 h. Particularly high temperatures that can be sustained without impairment of physical properties are exhibited by some plastics, which have engineering applications. A high, sustained melting temperature is often a particular requirement of such plastics. High maximum operating temperatures above 200 °C are possible with PEEK, PI, PAI and PPS (Table 3.3). GE Plastics developed a family of melt-processable, amorphous PI polymers that deliver ultra-high, thermal, chemical and mechanical properties [18]. According to GE, this family of PI resins will withstand high temperatures and harsh chemicals while remaining stiff and dimensionally stable. The Extem material also requires no

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Engineering Plastics post-moulding curing or crystallisation. Based on previously developed monomers, this resin line paved the way for developments in such industries as semi-conductor wafer handling, defence, oil and gas processing, aerospace, high-performance ibres, electronics and automotive applications. Sulfur containing polymers such as PPS, PES and PSU are particularly heat resistant and are suitable for high heat applications having maximum operating temperatures, of 200, 180 and 150 °C, respectively. PES and PSU are amorphous plastics with a high thermal durability that are used in engineering. They resist boiling water, organic solvents, chemical corrosion, and ignition and can easily be adapted for processing. This is the reason why they have recently been evaluated as possible replacements updated for conventional, thermally durable materials and for components used in aircraft, medical equipment, and automobiles. This means that more research and further evaluation are required: their pyrolysis behaviour and mechanisms are of paramount importance. PES is a semi-crystalline plastic with a high thermal durability used in engineering. It also resists organic solvents, chemical corrosion and ignition, and can be easily adapted for processing. This is the reason why it has been evaluated for the possibility of using it to replace conventional thermally durable materials and components used for packaging and in automobiles. The degradation study of PES is important because processing at high temperatures may produce changes that will affect the ultimate performance. Again, the studies of its pyrolysis behaviour and mechanism will be important for processing and performance evaluation.

3.6 Brittleness Temperature (Low Temperature Embrittlement Temperature) Brittleness temperatures are an assessment of the sub-zero temperature at which the material becomes brittle. A good or excellent rating indicates a low brittle temperature, i.e., it is serviceable at low temperatures. A poor rating indicates a high brittle temperature, i.e., it only has a limited sub-zero range of usefulness. An impact test for the measurement of brittleness is described in ASTM D746 [13]. It is important in some applications that the polymer does not embrittle outside a certain temperature range. Engineering plastics, which do not embrittle include LDPE, HDPE, PA, PTFE, ethylene-triluoroethylene copolymer, luorinated ethylenepropylene copolymer and silicones. PP, epoxy resins and polymethyl pentene are all subject to embrittlement.

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Thermal Properties of Polymers In cases of short-term exposure of up to a few hours, which would include sterilisation by autoclaving (typically 30 min at 134 °C), or paint drying (for example 20 min at 140 °C), then decisions taken on the basis of maximum operating temperatures may not be the most appropriate means of selecting candidate materials. For short exposure times there may not be any signiicant levels of oxidation or other chemical changes in the material that would lead to a loss in mechanical or physical properties. However, even short exposure to high temperatures can lead to loss of dimensional stability. In some cases, therefore, where the dimensional stability or stiffness of the materials at the maximum use temperature is more important, then it may be better to select materials on the basis of their heat distortion temperature (HDT).

3.7 Heat Distortion Temperature

3.7.1 Heat Distortion Temperature at 0.45 MPa (°C) The HDT at 0.45 MPa is the temperature, which causes a beam loaded to 0.45 MPa to delect by 0.3 mm. If the HDT is lower than the ambient temperature a value of 20 °C is given.

3.7.2 Heat Distortion Temperature at 1.80 MPa (°C) The heat distortion temperature at 1.80 MPa is the temperature which causes a beam loaded to 1.80 MPa to delect by 0.3 mm. If the HDT is lower than ambient temperature a value of 20 °C is given. Some polymers such as LDPE and HPDE, EVA copolymer, PU and plasticised polyvinyl chloride (PVC) distort at temperatures below 50 °C whilst others such as epoxies, PEEK, polyallylisophthalate, polydiallylphthalate, PC, alkyd resins, phenol-formaldehyde, PI, PEI, PPS, PES, PSU and silicones have remarkably high HDT in the range 150 to above 300 °C. TMA has been used to determine delection temperatures of polymers at selected temperatures and sample loading forces, i.e., plots of temperatures versus lexure. Nam and co-workers [19] used dynamic mechanical analysis (DMA) to measure the HDT of PPS/modiied ABS blends. The blend showed an enhanced thermal stability and an enhanced HDT when compared to a PPS/ABS blend. Rácz and co-workers [12] in their studies of PA 6-montmorillonite nanocomposites, measured HDT, tensile and impact strengths and deformation.

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Engineering Plastics

3.8 Thermal Conductivity Kazeminejad [20] has described the construction of an apparatus for the measurement of thermal conductivity accordingly to ASTM C177 [21] and DIN 52612-2 [22]. He describes a method of determining thermal conductivity of insulating materials, based on a copper-coated printed circuit board. Thermal conductivity values are reported for pure PE, pure PC, and PE and PC mixed with conductive illers such as aluminium powder and carbon black. Albrecht [23] used accelerated ageing processes to estimate the long-term change in thermal conductivity of a 10 year-old PU rigid foam board. The results provided safety increments to cover a lifetime which in practice is between 25−50 years. A research project was conducted to compare estimated increments with the change over time in thermal conductivity of real boards. Albrecht examined the thermal conductivity of the PU boards and the cell gas composition was determined over a period of 10 years. The shape of the curves and the measured values were compared with the typical diffusion coeficients and thermal conductivity of cell gases. The development of the curves showed that the ixed increments in the EN 13165 [24] standard for pentane blown PU foams had been correctly calculated. These ixed increments provided assurance for the users of PU rigid foam boards over very long periods e.g., 25 years, and gave conidence to builders and building supervisory authorities. Yu and co-workers [25] have reported the results of thermal conductivity measurements on polystyrene (PS)-aluminium nitride composites. Dos Santos and Gregorio, Jr., [26] measured the thermal conductivity of PA-PMMA, rigid PVC and PU foam. Prociak [27] studied the effect of parameters such as the method of sample preparation, the temperature gradient and the average temperature of measurement on the thermal conductivity of rigid PU foams blown with hydrocarbons and hydroluorocarbons (HFC). The thermal insulation properties of different cellular plastics, such as rigid and lexible PU foams and expanded PS, were compared. The thermal conductivity and thermal diffusivity of foams were correlated with the PU matrix structure to demonstrate the effect of cell anisotropy on the thermal insulation properties of the rigid foams blown with cyclopentane and HFC-365/227 (93 wt% pentaluorobutane/7wt% heptaluoropropane). Patton and co-workers [28] evaluated the ablation, mechanical and thermal properties of vapour grown carbon-ibre (VGCF; Pyrograf III from Applied Sciences Inc)/phenolic resin (SC-1008 from Borden Chemical Inc) composites to determine the potential of using this material in solid rocket motor nozzles. Composite specimens with

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Thermal Properties of Polymers varying VGCF loading (30-50 wt%) including one sample with ex-rayon carbonibre plies were prepared and exposed to a plasma torch for 20 s with a heat lux of 16.5 MW/m2 at about 1,650 °C. Low erosion rates and little char formation were observed, conirming that these materials were promising for use as rocket motor nozzle materials. When ibre loadings increased, mechanical properties and ablative properties improved. The VGCF composite had low thermal conductivities (about 0.56 W/m-K) indicating that they were good insulating materials. If a 65% ibre loading in VGCF composites could be achieved, then ablative properties were expected to be comparable with or better than the composite material currently used on the Space Shuttle reusable solid rocket motor. Researchers at LNP Engineering Plastics [29] reported use of a thermally conductive compound to encapsulate voice coil motors (VCM) in hard disc drives. LNP Engineering Plastics’ Konduit compound is a 55% ceramic-illed, 10% glass-reinforced PPS-based resin with a thermal conductivity of 1 W/mK, which is about three times the conductivity of unilled PPS. By encapsulating the VCM in the new compound, the device can handle more current, reducing seek time by 29%. Various other methods have been described for the determination of thermal conductivity. Capillarity has been used to measure the thermal conductivity of LDPE, HDPE and PP at various temperatures and pressures [30]. A transient plane source technique has been applied in a study of the dependence of the effective thermal conductivity and thermal diffusivity of polymer composites [31]. Transient hot wire methods are most extensively used to measure the thermal conductivity of polymers including PA, PMMA, PP, PVC, LDPE, and PS. This technique has been used by several researchers [26, 32-36]. Thermal conductivity studies have been conducted on a wide range of illed polymers and composites including carbon-ibres [2, 37-43], aluminium powder [40], aluminium nitride [41], magnetite, barite, talc, copper, strontium, ferrite [42], glass ibre illed PP [44] and manganese and/or iron illed polyaniline [42]. Chiu and co-workers [44] measured the cylindrical orthotropic thermal conductivity of spiral woven fabric composites using a mathematical model that they had devised previously. A parameter estimation technique was used to evaluate the thermal properties of spiral woven fabric composites to verify the predictability of the mathematical model. Good agreement was found between the temperatures measured in a transient heat conduction experiment and those calculated using the prediction equations formulated by the estimated parameters. Other polymers for which thermal conductivity data have been reported include PA

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Engineering Plastics 6,6, PMMA, rigid PVC, cellular PE [35], PVF [45], PTFE composites [3], PE ilms and PA ilms [46].

3.9 Specific Heat Sanderson and co-workers [47] measured the thermal properties of an epoxy shape memory polymer (SMP) foam, with a density of 18%, and found that the thermal diffusivity increased by an order of magnitude in going from fully expanded to fully compressed, while the thermal conductivity increased by almost as much. Under the same conditions, the speciic heat increased by less than 50% on average, while the density increased by a factor of about 3.5. Overall, the properties were, as expected, similar to those of a thermally-insulating material. A simple transient thermal analysis was then carried out to determine if this material could be used with an electric resistance heating element, as the skin of a morphing aircraft wing. At steady state, for a 9.5 mm thick SMP skin, the ratio of the maximum to minimum temperature within the material was found to be 21 for the compressed foam and 69 for the expanded foam, which was excessive for practical applications. A dense network of electric resistance heating elements embedded within the material would be required. The results presented emphasised the need to develop volumetric material heating systems if SMP were to be used extensively for morphing aircraft applications. Ranade and co-workers [48] showed that PAI-montmorillonite nanocomposites had a distinctly reduced speciic heat when compared to clay free polymer. Various techniques discussed in the next sections have been used to measure the speciic heat of polymers.

3.9.1 Hot Wire Techniques This technique has been used to measure the speciic heat of PA 6,6, PP, rigid PVC and cellular PU foam [26], epoxy resins, PTFE [49], PP [50], PMMA [51], HDPE, LDPE, PP, PS [52] and HDPE, LDPE, PP and PS [53].

3.9.2 Transient Plane Source Technique The laser lash technique has been used to measure the speciic heat of ibre-reinforced phenol-formaldehyde resins [31]. This technique has also been used to determine the speciic heat of PVDF [45, 52].

66

Thermal Properties of Polymers

3.10 Thermal Diffusivity Thermal diffusivity measurements have been reported for fibre reinforced phenol-formaldehyde resins [31], PA 6,6, PP, PMMA [54] and triluoroethylene nanocomposites [55]. Laser lash techniques have been used to determine the diffusivity of pyroelectric polymers such as PVDF [45, 52] whilst hot wire techniques have been used to determine the thermal diffusivity of HDPE, LDPE, PP and PS [36]. Nunes Dos Santos and co-workers [56] utilised the laser lash technique to study the effect of recycling on the thermal properties of some selected polymers. Since the thermal diffusivity expresses how fast heat propagates across a bulk material and the thermal conductivity determines the working temperature levels of a material, it is possible to state that these properties are important when a polymer is used as an insulator and also when it is used in applications where heat transfer is desirable. Five sets of virgin and recycled commercial polymers widely used in many applications, including food wrapping were selected for this study. Disc-shaped samples 10 mm diameter and 0.3-1 mm thickness were prepared by hot pressing the polymer pellets or powder, or by cutting discs from long cylindrical bars. Measurements were carried out from room temperature up to approximately 50 °C above the polymer crystalline melting point. Experimental results show different behaviour for the thermal diffusivity of recycled polymers when compared with the corresponding virgin material.

3.11 Thermal Insulation Index Kusan-Bindels and Friedrichs [57] have discussed the measurement of this property in rigid polyisocyanurate foams. An increase in the thermal insulation index of this polymer improves temperature stability and mechanical properties, even at 250 °C.

3.12 Glass Transition Temperatures The Tg is deined as the temperature at which a material loses its glass-like, more rigid properties and becomes rubbery and more lexible in nature. Practical deinitions of Tg differ considerably between different methods, therefore, speciication of Tg requires an indication of the method used. Amorphous polymers when heated above their Tg change from the hard to the soft state.

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Engineering Plastics During this process, relaxation of any internal stress occurs. At the Tg many physical properties change abruptly. Some of these are very important when considering the selection of polymers for engineering applications. These properties include Young’s Modulus and shear strength, speciic heat, coeficient of expansion, and dielectric constant. For hard polymeric material this temperature corresponds to the highest working temperature; for elastomers, it represents the lowest working temperature. Several methods exist for determining Tg, these include DTA, DSC, TMA, dilatometry, DMA and nuclear magnetic resonance (NMR), spectroscopic methods as discussed in the next sections. Each method requires interpretation to determine Tg. For this reason exact agreement is frequentlynotobtained between results obtained by different methods. The reported Tg of polymers cover a wide range of values ranging from -80 to -100 °C for polybutadiene and LDPE, and up to 100 °C for PMMA. Tg is shown by a change in the expansion coeficient and the heat capacity as a sample material is heated or cooled through this transition region. Sometimes more than one Tg value is obtained. Thus, 5-(N-carbazoyl methyl) bicyclo(2,2,1) hept-2-ene and 5-(phthalmimide methyl) bicyclo (2,2,1) hept-2enediblock copolymers gave two Tg values corresponding to the 5-(N-carbazoyl methyl (bicyclo (2,2,1)hept-2-2-ene and the 5-(phthalimide methyl) bicyclo (2,2,1) hept-2-ene segments before and after hydrogenation. The unhydrogenated diblock copolymer showed better oxidative stability and poorer heat stability than the hydrogenated copolymers. PEEK-polyaryl ether sulfone blends gave two Tg values corresponding to a PEEK rich blend and a polyaryl ether sulfone rich blend. Binary polylactide-polyvinyl pyrolidone blends also exhibited two Tg values. Numerous techniques have been applied to the measurement of Tg [58-75] including DSC, [76] thermogravimetric analysis (TGA), DTA, DMA, TMA, dielectric thermal analysis (DETA) and NMR spectroscopy. Figure 3.1 shows a TMA curve of epoxy resin measured in nitrogen at a heating rate of 5 °C/min - this indicates a Tg value of 125 °C. Dynamic mechanical thermal analysis (DMTA) [76] is more sensitive to material transitions than traditional thermal analysis techniques (e.g., DSC, DMTA). Detection of major transitions such as Tg, for example, by DMTA, is easier in highly illed or reinforced materials because the material’s modulus changes by several orders of magnitude at the Tg, while the material heat capacity (the basis of DSC detection) and expansion coeficient (the basis for DMTA detection) change

68

Thermal Properties of Polymers less signiicantly. Moreover, the detection of weak secondary transitions is possible only by DMTA.

0.10 0.09 0.08

Expansion (mm)

0.07

T1 112.020 °C T2 149.963 °C Onset 128.246 °C Y value 0.019 mm Glass transition (Tg)

0.06 0.05 0.04 0.03 0.02 0.01 0.00 75 Force = 10 mN

100

125 150 Temperature (°C)

175

200

Figure 3.1 TMA of epoxy resin measurements of Tg. Source: Author’s own iles

TMA is the measurement of dimensional changes (such as expansion, contraction, lexure, extension and volumetric expansion and contraction) in a material by movement of a probe in contact with the sample used to determine temperature related mechanical behaviour in the temperature range -180 to 800 °C as the sample is heated, cooled (temperature plot), or held at a constant temperature (time plot). It also measures linear or volumetric changes in the dimensions of a sample as a function of time and force. Plots of sample temperature versus dimensional (or volume) changes enable the Tg to be obtained. The Tg is obtained from measurement of sudden changes in the slope of the expansion curve. In the thermo-mechanical analyser, a quartz probe closely monitors dimensional changes in the sample being studied. The position of this probe is continuously monitored by a high-sensitivity, linear variable displacement transducer. The transducer itself is temperature controlled to provide excellent

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Engineering Plastics stability and reproducibility. The probe mechanism is controlled through a closed loop electromagnetic design circuit. This design allows precise probe control, computer controlled application of force to the sample and constant sample loading throughout the experiment. These features provide exceptional temperature control from -170 to 1,000 °C. Gómez-Elvira and co-workers [77], Schmidt-Rohr and Speiss [78] used DMTA to measure the Tg and α-relaxation of a metallocene polypropylene sample and an isotactic polypropylene sample, respectively. The spectra of the dynamic mechanical relaxations were obtained using rectangular sample strips (typical dimensions being 8 × 40.6 mm) with a DMA analyser in lexion mode. The temperature dependance of the loss modulus was determined with at 0.1 Hz, between -150 and 130 °C, at a heating rate of 5 °C/min and using a deformation amplitude of 1 mm. Relaxations obtained at a temperature of less than 90 °C are seen better by using DMA. The same three relaxations as in isotactic Ziegler-Natta PP appear [79], i.e., the low temperature of relaxation is at about -60 °C, the Tg at about 90 °C and the relaxation at 60 °C.

3.13 Alpha, Beta and Gamma Transitions In the dynamic mechanical loss spectra of polymers, the transitions that are related to different molecular motions within polymers are called α, β and γ transitions. The α transition involves long segments of the polymer chain where the movement causes other chain segments to move out of the way. These ‘cooperative main-chain motions’ are increasingly prevalent at the Tg and can be used to deine the Tg of a material. The β transition involves chain segments that are shorter than those in α transitions. For that reason, they occur below the Tg of the material. The motion producing the γ transition involves short chain segments. In many polymeric systems, the γ transition is caused by the ‘crankshaft rotation’ of the methylene (-CH2-) groups on a long polymer chain. Since the γ transition involves those molecular segments, it occurs below the α and β transitions. Six techniques have been used to detect transitions other than Tg in polymers. These include DTA, DMA, DETA, infrared (IR) spectroscopy, DSC and TMA.

70

Thermal Properties of Polymers

3.13.1 Dynamic Mechanical Analysis DMA is more sensitive to material transitions than traditional thermal analysis techniques (e.g., DSC, TMA). Detection of major transitions such as the Tg, for example, by DMA, is easier in highly illed or reinforced materials because the material modulus changes by several orders of magnitude at the Tg, while the material heat capacity (the basis for DSC detection) and expansion coeficient (the basis for TMA detection) changes less signiicantly. Moreover, the detection of weak secondary transitions is possible only by using DMA. DMA is sensitive enough to detect even weak secondary transitions such as α and β transitions in the resin matrix of a highly illed composite. In fact, all properties measured by this technique generate strong, well-deined signals that are not clouded by background noise or other interference. The shear storage modulus (g) versus temperature (Figure 3.2) demonstrates the three thermal induced transitions occurring in a semi-crystalline Nylon 6,6.

0.28

Tensile loss modulus (GPa)

0.24 0.20

γ

0.16

High density (linear)

0.12 0.08 0.04

α Low density (branched)

β

0.00 -140 -120 -100 -80

-60 -40 -20 0 Temperature (°C)

20

40

60

80

Figure 3.2 Shear storage modulus plot for semi-crystalline Nylon 6,6 demonstrating α, β and γ transitions. Source Author’s own iles

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Engineering Plastics Figure 3.3 compares the loss modulus (damping) at three different measurements of linear (HDPE) and branched (LDPE) polyethylene, showing three transitions, α at 80 °C, β at -5 °C and γ at -110 °C. Each of these transitions corresponds to speciic molecular motions which has signiicance in terms of structure-property relationships: •  The α transition is associated with crystalline relaxations occurring below the melting point of PE. •  The β transition is due to motion of the amorphous region side chains or branches from the main polymer backbone. The intensity of the β transition varies with the degree of branching. •  The γ transition is a result of crankshaft rotation of short methylene main chain segments and can inluence the low temperature impact stability of PE. Figure 3.3 shows a shear stress versus temperature plot for HDPE and LDPE.

Osc Amp: 0.20

4.0

0.12

0.10

2.8

0.08

β γ

2.4

0.06

2.0

0.04

1.8

0.02

] Shear loss modulus (GPa)

α 3.2

[

[

] Shear storage modulus (GPa)

3.6

0.14

1.2 -140

0.00 -120

-100

-80

-60

-40

-20

0

20

40

60

80

Temperature (°C)

Figure 3.3 DMA comparison of LDPE and HDPE. Source: Author’s own iles

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Thermal Properties of Polymers

3.13.2 Differential Thermal Analysis A linear high-pressure PE blend upon heating, undergoes three phase changes from its high-pressure form: the 115 °C peak is associated with the high-pressure PE, whereas the 134 °C is shown to be proportional to the linear content of the system. Clampit [80] also applied DTA to a study of the 124 °C peak which he describes as the co-crystal peak. His results appear to indicate that there are two classes of co-crystals in linear high-pressure PE blends with the linear component being responsible for the division of the blends into two groups. The property of the linear component that is responsible for the division is related to the crystallite size of the pure linear crystal.

3.13.3 Infrared Spectroscopy While thermal methods for the determination of polymer transitionspredominate, IR spectroscopy has been used to provide information on temperature transitions. Varob’yev and Vettegren [81] used IR spectroscopy to determine temperature transitions in PC. Thermal transitions in PC were determined from the concentration variations of the residual solvent or plasticiser. Structural transitions and relaxation phenomena of PC have been followed by plotting the absorbance at 8.13 µm (stretching vibration of C-O-C groups) and 10.64 µm against temperature [82].

3.13.4 Dielectric Thermal Analysis DETA, which measures a material’s response to an applied alternating voltage signal, provides an excellent means of characterising thermoplastics. DETA measures two fundamental electrical characteristics, capacitance and conductance, as a function of temperature, time and frequency. The capacitive nature of a material relects its ability to store an electrical charge and this property dominates the electrical response at temperatures below the Tg. The conductive nature is the ability to transfer electrical charge and generally dominates the electrical response at temperatures above the Tg or Tm. While these electrical properties are important in themselves, they acquire more signiicance when they are correlated to changes in the molecular state of the material. The actual properties monitored using dielectric analysis are ɛʹ (permittivity), which is a measure of the degree of alignment of the molecular dipoles to the applied electrical ield, and eʹʹ (loss factor), which represents the energy required to align the dipoles or to move trace ions.

73

Engineering Plastics The ultra-sensitivity of this technique makes it possible to detect transitions that are not seen by other techniques. Its ability to measure bulk or surface properties of materials in solid, paste, or liquid form makes DETA versatile and very useful. The α transition, which involves motion in long segments of the main polymer chain, is related to the Tg. The β transition involves rotation of short-chain ester side groups in PMMA and therefore occurs below the Tg. The frequency dependency of the β-Tg can be used to calculate the activation energy for the molecular motion, which provides important information for characterising the structure and predicting the performance of polymeric materials. In a dielectric experiment, the calculated activation energy for the β transitions in PMMA was 17.7 kcal/mol. This correlates well with the values calculated from DMA and creep experiments. Figure 3.4 shows α and β transitions obtained in DETA of PET. The α transition (Tg) is affected by the large scale micro-Brownian motion in the amorphous (noncrystalline) phase. The Brownian motion is observed as a peak in the 1 Hz loss factor curve at about 90 °C. The β transition is considered to be a result of main chain motion including the ester groups.

3.14 Developments in High Temperature Plastics

3.14.1 Introduction In certain applications of plastics in engineering there is a need for materials which have a very high resistance to temperatures of 500−600 °C whilst avoiding decomposition and retaining their original physical properties. Some particular applications that require such polymers include components in hot engine compartment, applications in electronics and, most recently, the development of materials for use in aircraft fuselages and parts used in the construction of jet engines, where prolonged exposure to temperatures exceeding 400−500 °C might be a consideration. Recently developed high temperature polymers, which can be considered for use in such applications include PI, luorinated PI, PAI, PEI, PPS and its disulide, PES and PSU, details of which are incorporated in Table 3.4.

74

Thermal Properties of Polymers 3.2

e′ (premium)

3.0 2.8

(a)

Parallel plate sensors Polyethylene terephthalate Heating rate = 3 °C/min Frequency = 1, 3, 10, 30, 100, 300 Hz 1, 3, 10, 30, 100 kHz

2.6

2.4

2.2 -150

-100

-50

0 50 Temperature (°C)

100

150

200

e′′ Loss factor

0.06

0.04

(b) Parallel plate sensors Polyethylene terephthalate Heating rate = 3 °C/min α Frequency = 1, 3, 10, 30, 100, 300 Hz 1, 3, 10, 30, 100 kHz β

0.02

0.00 -150

-100

-50

0 50 Temperature (°C)

100

150

200

Figure 3.4 Resolution of multiple transitions in amorphous PET by DETA (a) eʹcurves deining PET transistions, and (b) eʹʹ showing frequency of α-β transitions. Source: Author’s own iles

75

76 160 170 -

170 200 180 180 250 150

160

130 -

PEI PPS PES PSU PEEK Fluorinated ethylene-PP Ethylenetetraluoroethylene Epoxy composites Organosilicon compounds

Source: Author’s own iles

180 180 250 -

210

Fluorinated PI PAI

196-230 -

Greater than 200

PI

0.3 -

3

0.3 0.6 0.7 1.2 -

0.7

>260 -

105

150 >260 150 179 >260 70

>260

230 -

71

300 244 300 174 160 50

274

Continuous use Mould Heat distortion temperature (°C) shrinkage (%) temperature (°C) 0.45 MPa 1.8 MPa >260 230

Max operating temperature (°C)

Polymer

Weight loss occurs between 250−260 °C in air, and at 380−400 °C under nitrogen

-

No heat loss between 370−430 °C. At temperatures of 316−538 °C, there is asustained retention of physical properties 440−500 °C 1% weight loss under nitrogen at 575 °C 430 °C No weight loss between 450−470 °C 500°C 500 °C -

Temperature at which weight loss starts (°C)

Table 3.4 High temperature resistant engineering polymers

Engineering Plastics

Thermal Properties of Polymers Other polymers of possible interest in applications involving high temperatures include epoxy resin composites, PEEK, organosilicon compounds and highly luorinated ethylene-propylene and ethylene tetraluoroethylene polymers. TGA is a very useful technique for evaluating any weight changes in polymers as they are exposed to particular temperature rises for certain periods of time. Such weight changes might be due to (a) weight loss accompanying structural change in the polymer with exposure to heat, or (b) to loss of volatile components of the polymer such as water or solvents or to a combination of these two. Differential thermogravimetry thermograms obtained from various polymers are illustrated in Figure 3.5. Thermogravimetric curves for PE and PP-PE blends, shown in Figure 3.5a and Figure 3.5b, respectively, show inlections at approximately 375–380 °C. More heat resistant polymers are represented by curves shown in Figure 3.5c and Figure 3.5d for PTFE and PES, which show inlections at about 500 and greater than 600 °C, respectively. Other high heat resistant polymers include PPS, PSU, PES and PI.

Weight loss, mg

0

50

100

300

350

400 Temperature (°C)

450

487

77

Engineering Plastics

(i) HDPE Blend Blend Blend Blend Blend Blend Blend

60

Mass (%)

80

PP ×0 Calculated

×0 ×0 ×1 ×2 ×3 ×4 ×5 ×6

40

20

0

Temperature 340

360

380

400

420

440

460

480

500

°C

120 (ii)

100 Blend ×4 Blend ×3 Blend ×2 Blend ×1 Blend ×0

Mass (%)

80 60

Blend ×5

40

Blend ×6

PE ×0

20 0 200

PP ×0

250

300

350

400

Temperature (°C)

78

450

500

550

Thermal Properties of Polymers 0 10

Weight loss, mg

20

Air

30 40 50

Teflon 50% S1O2 (100.0 mg sample)

60 70

Teflon 10% S1O2 (101.0 mg sample) Teflon (102.0 mg sample)

80 90

Teflon 25% S1O2 (104.0 mg sample)

100

100 200 300 400 500 600 700 800 900 Temperature (°C)

60

50

SO2 Benzene Phenol Diphenylether Dibenzofuran

Yield (mol%)

40

30

20

10

0 400

500

600

700

800

900

1000

1100

Pyrolysis temperature(°C)

Figure 3.5 (a) Thermogravimetric curve for the degradation of PE at 133 MPa pressure. The sample weight was 100 mg and the heating rate was 5 °C/min. (b) TGA of PE-PP blends (i) under nitrogen, and (ii) under oxygen. (c) TGA of PTFE and polytetraluorosilica mixtures in air. (d) Pyrolysis gas chromatographic analysis curves of PES. Source: Author’s own iles

79

Engineering Plastics

3.14.2 Polyimides PI has been intensively studied since the 1960s because of its good thermal stability. TGA is one of the major characterisation techniques for such a study. PI are increasingly used in the electronics and telecommunications industries. However, the commercially available PI have some disadvantages, such as low optical transparency and a high dielectric constant. Considerable attention had been drawn to the synthesis and application of luorine-containing PI because of their unique properties. Thus, the incorporation of luorine groups, such as hexaluoroisopropylidene moieties, into the PI structures has been explored extensively in past decades. However, their thermal degradation mechanisms have been investigated less often. A PI based on a 2,2ʹ-dimethylbenzidine carbon ibre composition can endure service temperatures up to 335 °C whilst carbon nanotube formulations have an even higher service temperature of up to 800 °C and lexural shear strength up to 115 kg/ cm2 at 316 °C. McConnell [83] reports that composites based on PI have sustained temperatures in the range of 516−538 °C. Various researchers have discussed the thermal properties of PI [84-89].

3.14.3 Fluorinated Polyimides Decomposition temperature data has been reported for PI based on 2,2ʹ-bis(4-amino2-triluoromethylphenoxy)biphenyl or 2,2ʹ-bis(4-amino-2-triluoromethylphenoxy)1-1ʹ-binapthyl [90, 91] and PI based on 1,4-bis(4-amino-2-triluoromethylphenoxy) naphthalene [92]. The former had a decomposition temperature of 520 °C under air or nitrogen for a 10% weight loss (and the latter had a decomposition temperature above 500 °C under air or nitrogen for a 5% weight loss and a decomposition temperature which was above 400 °C for a 10% weight loss under air or nitrogen.

3.14.4 Polyamide-imide Various researchers have reported on the thermal properties of PAI derived from bis(4-trimellitimidephenyl) urea [93] and PAI-polydimethylsiloxane nanocomposites [94]. The former polymer had a decomposition temperature of 515 °C under nitrogen for a 10% weight loss.

3.14.5 Polyether-imide PEI has excellent mechanical properties and, in addition to high thermal stability,

80

Thermal Properties of Polymers remains stable during injection moulding operations carried out at temperatures above 300 °C [95].

3.14.6 Polyphenylene Sulfide PES and PPS are, amongst others, being used in the manufacture of aircraft, in high temperature under-the-bonnet applications, in medical equipment that requires sterilisation and in critical packaging applications and in the electronics and telecommunications industry. Perng [95] used thermogravimetry-mass spectrometry (TG-MS) under helium to investigate in detail, the nature of the decomposition products produced when PPS is heated to temperatures up to 700 °C. It is seen in Figure 3.6 that no volatiles are produced at temperatures below 450 °C indicating that the polymer structures remain unchanged up to this temperature.

120

1.0

533°C 0.81%/°C 100

80

0.6

60

0.4

Residue: 30.4% 40

(a)

Deriv. weight (%/°C)

Weight (%)

0.8

0.2

(b) 20 400

500

600 700 Temperature (°C)

800

0.0 900

Figure 3.6 TGA of PPS. Reproduced with permission from L.H. Perng, Polymer Degradation and Stability, 2000, 69, 3, 323. ©2000, Elsevier [95]

81

Engineering Plastics

3.14.7 Polyxylenyl Sulfide Montaudo and co-workers [96] investigated the thermal degradation of polyxylylene sulide and polyxylylene disulide and showed that these polymers decompose in two steps in the temperature ranges 250−280 °C and 600−650 °C leaving a high amount of residue (see Figure 3.7). Products released included benzenethiol and hydrogen sulide indicating that chain scission had occurred.

Thermogravimetry

% Residue

100 PXD

PXM

50 PXD

PXM

0 100

200

300 400 500 600 Temperature (°C)

700

Figure 3.7 Thermogravimetric curves for PXD and PXM. PXD: polyxylenyldisulide. Reproduced with permission from I.G. Montaudo, C. Puglisi, W. de Leeuw, W. Hartgers, K. Kishori and K. Ganesh, Macromolecules, 1996, 29, 6466. ©1996, ACS [97]

3.14.8 Polyether Sulfone and Polyphenylene Sulfide Figure 3.8 shows a distribution pattern of volatiles produced during the heating of PES as measured by a combination of TGA and stepwise pyrolysis-gas chromatographymass spectrometry [95], which indicates that the major products, sulfur dioxide and phenol, are not produced at temperatures below 450 °C.

82

Thermal Properties of Polymers (a)

Ion 110

Benzenthiol

10000 0

Abundance

Hydrogen sulfide

Ion 34

10000 0

Benzene

Ion 78 2000 0

0 400

Carbon disulfide

Ion 76

500

450

500

550 600 650 Temperature (°C)

(b) 1000

700

750

Ion 142

1.4-Benzenedithiol

Ion 124

4-Methylbenzenethiol

800

0

Abundance

200 0 Ion 186

2000

Diphenyl sulfide+biphenylthiol

0 Ion 154 500 0 400

450

(c)

500

550 600 650 Temperature (°C)

Ion 184

2000

Biphenyl

700

750

800

Dibenzothiophene

1500 1000

Abundance

500 0 Ion 218

600

4-Thiodiphenyl sulfide

400 200 0 400

450

500

550

600 650 Temperature (°C)

700

750

800

Figure 3.8 (a) Change of PPS pyrolysis products in TG-MS in helium at 10 °C/min: (1) benzenethiol; (2) hydrogen sulide; (3) benzene; and (4) carbon disulide; (b) change of PPS pyrolysis products in TG-MS in helium at 10 °C /min: (1) 1,4-benzenedithiol; (2) 4-methylbenzenethiol; (3) diphenylsulide + biphenyl thiol; and (4) biphenyl; (c) change of PPS pyrolysis products in TG-MS in helium at 10 °C/min: (1) dibenzothiophene, and (2) 4-thiodiphenylsulide. Reproduced with permission from L.H. Perng, Polymer Degradation and Stability, 2000, 69, 3, 323. ©2000, Elsevier [95]

83

Engineering Plastics

3.14.9 Organosilicon Polymers On the whole, organosilicon polymers do not have an especially high resistance compared to that which is available in other polymers. Thus, the decomposition of the trimethylsiloxy substituted polyoxadisilapentanylenes starts at 315 °C in nitrogen but is as low as 190 °C in air [97].

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Thermal Properties of Polymers 45. W. Nunes dos Santos, C.Y. Iguchi and R. Gregorio, Jr., Polymer Testing, 2008, 27, 2, 204. 46. H. Wu and J. Fan, Polymer Testing, 2008, 27, 1, 122. 47. T. Sanderson, M.A. Di Prima, K. Gall, J. Lamb and S. Arzberg in Proceedings of the SAMPE Fall Technical Conference – From Art to Science: Advancing Materials and Process Engineering, Cincinnati, OH, USA, 2007, Paper No.62. 48. A. Ranade, N.A. D’Souza and B. Gnade, Polymer, 2002, 43, 13, 3759. 49. A.J. Panas and S. Cudziło, Journal of Thermal Analysis and Calorimetry, 2004, 77, 1, 329. 50. V.P. Privalko, V.B. Dolgoshey, E.G. Privalko, V.F. Shumsky, A. Lisovskii, M. Rodensky and M.S. Elsen, Journal of Macromolecular Science Part B, 2002, 41, 3, 539. 51. C. Chaui, K. Almdal and J. Lyngaae-Jørgensen, Journal of Applied Polymer Science, 2004, 91, 1, 609. 52. C.Y. Iguchi, W.N. Dos Santos and R. Gregorio, Jr., Polymer Testing, 2007, 26, 6, 788. 53. B-C. Chern, T.J. Moon and J.R. Howell, Journal of Composite Materials, 2002, 36, 16, 1905. 54. Rubber Asia, 2003, 17, 93. 55. M. Aravind, C.W. Ong and H.L.W. Chan, Polymer Composites, 2002, 23, 5, 925. 56. W. Nunes dos Santos, J.A. Marcondes Agnelli, P. Mummery and A. Wallwork, Polymer Testing, 2007, 26, 2, 216. 57. J. Kusan-Bindels and W. Friedrichs, Polyurethane Magazine, 2004, 1, 37. 58. W.P. Yang, C. Wise, J. Wijaya, A. Gaeta and G. Swei in Proceedings of the Rad Tech ’96 North America Conference, Nashville, TN, USA, 1996, Volume 2, p.675. 59. F.R. Diaz, J. Moreno, L.H. Tagle, G.A. East and D. Radic, Synthetic Metals, 1999, 100, 2, 187

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Engineering Plastics 60. R.G. Ferrillo and P.J. Achorn, Journal of Applied Polymer Science, 1997, 64, 1, 191. 61. M.H. Alma and S.S. Kelly, Polymer Degradation and Stability, 2000, 68, 3, 413. 62. A.K. Sircar, M.L. Galaska, S. Rodrigues and R.P. Chartoff in Proceedings of the 150th ACS Rubber Division Fall Meeting, Louisville, KY, USA, 1996, Paper No.35. 63. H-Q. Zhang, W-Q. Huang, C-X. Li and B-L. He, European Polymer Journal, 1998, 34, 10, 1521. 64. S.C. Tjong and W. Jiang, Journal of Applied Polymer Science, 1999, 73, 11, 2247. 65. J. Reiger, Polymer Testing, 2001, 20, 2, 199. 66. X. Hu and L. Xu, Polymer, 2000, 41, 26, 9147. 67. M. Kluppel, R.H. Schuster and J. Schaper in Proceedings of the 151st ACS Rubber Division Spring Meeting, Anaheim, CA, USA, 1997, Paper No.54. 68. J.Z. Liang, R.K.Y. Li and S.C. Tjong, Journal of Thermoplastic Composite Materials, 2000, 13, 1, 12. 69. N.W. Johnston, Journal of Macromolecular Science: Part A - Chemistry, 1973, 7, 2, 531. 70. A.V. Savitskii and I.A. Gorshkova, Polymer Science Series A, 1997, 39, 3, 356. 71. A. Georgiades, I. Hamerton, J.N. Hay, H. Herman and S.J. Shaw, Polymer International, 2004, 53, 7, 877. 72. H. Wohltjen and R. Dessy, Analytical Chemistry, 1979, 51, 9, 1465. 73. C.L. Beatty and M.F. Froix, Polymer Preprints, 1975, 16, 2, 628. 74. J.B. Smith, A.J. Manuel and I.M. Ward, Polymer, 1975, 16, 1, 57. 75. E.J. Nelson, S.H. Foulger and D.W. Smith, Jr., High Performance Polymers, 2001, 13, 3, 101.

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Thermal Properties of Polymers 76. M. Thayumanaswamy and V. Rajendren, Journal of Applied Polymer Science, 2004, 93, 3, 1305. 77. J.M. Gómez-Elvira, P. Tiemblo, M. Elvira, L. Matisova-Rychla and J. Rychly, Polymer Degradation and Stability, 2004, 85, 2, 873. 78. K. Schmidt-Rohr and H.W. Spiess, Macromolecules, 1991, 24, 19, 5288. 79. P. Tiemblo, J.M. Gómez-Elvira, S. Garcia Beltrán, L. Matisova-Rychla and J. Rychly, Macromolecules, 2002, 35, 15, 5922. 80. B.H. Clampitt, Journal of Polymer Science, Part A: General Papers, 1995, 3, 2, 671. 81. V.M. Varob’yev and V.I. Vettegren, Polymer Science USSR, 1975, 17, 2, 520. 82. G.G. Andronikashivili, S.A. Samsoniya, M.G. Zhamierashvili and M. Soolesch, Akademii Nauk Gruz SSSR, 1977, 85, 73. [Chemical Abstracts, 1977, 86, 190545C] 83. V.P. McConnell, High-Performance Composites, 2009, 17, 4, 39. 84. J-Y. Lee, C.S. Baek and E-J. Park, European Polymer Journal, 2004, 41, 9, 2107. 85. D. Cho, S. Lee, G. Yang, H. Fukushima and L.T. Drzal, Macromolecular Materials and Engineering, 2005, 290, 3, 179. 86. M.L. Bessonove, M.M. Koton, V.V. Kudryavstev and L.A. Laius in Polyamides – A New Class of Thermostable Polymers, Nauka, Leningrad, Russia, 1983. 87. P.N. Gribikova, V.V. Rode, S.Y. Vygodskii, S.V. Virogradova and V.V. Korshak, Vysokomolekulyarnye Soedineniya Seriya, 1970, 12, 220. 88. B.M. Kovarskaya, A.B. Blyumenfeld and S.L. Levantovskau in Thermal Stability of Hetrochain Polymers, Kimiya, Moscow, Russia, 1977. 89. M.J. Turk, A.S. Ansari, W.B. Alston, G.S. Gahn, A.A. Frimer and D.A. Scheiman, Journal of Polymer Science, Part A: Polymer Chemistry Edition, 1999, 37, 21, 3943. 90. C-P. Yang, S-H. Hsiao, C-Y. Tsai and G-S. Liou, Journal of Polymer Science, Part A: Polymer Chemistry Edition, 2004, 42, 10, 2416.

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90

4

Electrical Properties of Polymers

4.1 Introduction Some of the electrical applications to which unreinforced and reinforced engineering plastics have been put are listed in Table 4.1 and Table 4.2, respectively.

Table 4.1 Electrical applications of unreinforced engineering polymers Polymer PP Epoxy resins PEEK, polydiallyl phthalate

Application Electrical insulation Electrical components Wire covering electrical connectors, switchgear housing and bush holders Electrical switchgear, electrical ittings and connectors Electrical components, switches and motor components Electrical connectors Electrical mechanical components Electrical and electronic applications, cable and wire covering Capacitors, cable insulation and printed circuit boards Electrical connectors Electrical connectors and printed circuit boards Electrical and electronic components Electrical and electronic components and switch housings Wire coatings and electrical components

PC, PET PBT PA 6 PA 11 PA 12 PA PEI PAI PES PSU Perluoroalkoxyethylene, luorinated ethylenepropylene PA: Polyamide PAI: Polyamide-imide PBT: Polybutylene terephthalate PC: Polycarbonate PEEK: Polyether ether ketone PEI: Polyether-imide PES: Polyether sulfone PET: Polyethylene terephthalate PP: Polypropylene PSU: Polysulfone Source: Author’s own iles

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Table 4.2 Electrical applications of reinforced engineering plastics Polymer Alkyd resin (long glass ibre) Alkyd resins (short glass ibre) Alkyl resins (mineral and glass ibre) Diallyl isophthalate (long glass ibre) Diallyl phthalate (long glass ibre) Diallyl phthalate (mineral) Diallyl phthalate (short glass ibre) Epoxy resins (glass ibre)

Epoxy resins (mineral and glass ibre) Epoxy resins (silica) Fluorinated ethylene-propylene (20% glass ibre) PA 11 (30% glass ibre) PA 12 (30−50% glass fibre) PA 6 (30% glass fibre) PA 6,10 (30% carbon fibre) PA 6,10 (30% glass fibre) PAI glass-fibre PBT (10−20% short glass fibre) PC (20−30% glass fibre) PEEK (20−35% glass fibre) PEI (10−30% glass fibre) PES (30% glass fibre) PET (30−45%) glass fibre

PI (40% glass fibre) PP (20% talc) PPS (40% glass fibre)

Application Switching and insulations Automotive ignition switches and relay bases Switches, relays bases and capacitor encapsulation Switchgear and brush holders Electrical connectors, relays and switches Relays and switches communicators Connectors, relays, switchgear and brush holders Encapsulated electronic and electrical devices, capacitor and resistor protection and switchgear insulation Encapsulation of electronics and electrical devices, protection of capacitors and resistors Transformers, capacitor case and electrical connectors Electrical components Electrical plugs Electrical coils and bobbins Electrical connections and plugs Electrical components Electrical plugs Terminal strips and insulators Lamp sockets, switches, motor housings and electrical parts Electrical enclosures and relay separators Electrical components and printed circuit boards Electrical components, fuses, electrical components, switches and printed circuit boards Electrical components and printed circuit boards Electrical components and terminal blocks

Terminal boards Electrical systems housing Boxes for electronic circuits, relays, circuit breakers, terminal blocks, connectors and electronic motor housings PSU (10% glass fibre) Electrical components, printed circuit boards and electronic ignition components PSU (30% carbon fibre) Switch devices Silicone (glass and mineral and glass fibre) Electronic components encapsulation Silicones (mineral and glass fibre) Electronic components encapsulation PI: Polyimide PPS: Polyphenylene sulfide Source: Author’s own files

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Electrical Properties of Polymers It can be seen that these polymers can be used in a very wide range of engineering applications ranging from wire and cable coverings, insulators, transformers, to use in the fabrication of electronics and electrical components. The importance of various electrical properties in relation to their applications cannot be overemphasised. Deinitions of important electrical properties are given in the next sections.

4.1.1 Dielectric Constant The dielectric constant of a material is deined as the ratio of the capacitance of a particular capacitor containing the material to that of the same capacitor when the material is removed and replaced by air, i.e., the ability of a substance to store electrical energy in an electric ield. The dielectric constant varies with frequency and generally increases with temperature.

4.1.2 Dielectric Strength (V/m) The dielectric strength is the voltage that an insulating material can withstand before dielectric breakdown occurs. Note that dielectric strength generally increases with decreasing specimen thickness. The values given in Table 4.3 are typical dielectric strength values at room temperature, for a 3 mm thick specimen.

93

94

PET PEEK Polyarylates Alkyd resins PPO Phenol-formaldehyde Styrene-maleic anhydride copolymer PMMA EVA

PBT PC 16 16 16 15 17 10 15

GP 14 25% vinyl 16 acetate

GP GP GP GP GP GP GP

15 14

2 15 14

GP GP GP phenyl polyester GP GP

18 27

40 19 15.1 13 21 12 12

20 20

20 13

3.3 2.9

3.5 3.2 3.13 6.1 2.6 8 2.5

3.2 3.2

3.7 5.0

2.2

GP

26

16

GP GP GP GP GP GP

LDPE Crosslinked polyethylene HDPE PP Polymethyl pentene Ethylene-propylene copolymer Styrene-ethylene-styrene copolymer Epoxy resins Polyacetals Polyesters

Table 4.3 Electrical properties of polymer Volume resistivity Dielectric Dielectric (ohm.cm) strength (mV/m) constant at 1 kHz 16 27 2.3 16 21 2.2 17 22 2.3 15 18 2.6 16 28 2.12 15 30 2.3

Grade

Polymer

0.02

0.01 0.0016 0.005 0.012 0.0004 0.05 0.001

0.002 0.03

0.0015 0.01

0.006

0.0003 0.0004 0.0005 0.10 0.0002 0.0005

Dissipation factor at 1 kHz

Excellent Poor

Excellent Very good Very good Very poor Very poor Poor

Good Very poor

Poor Poor -

Good

Very good Very good Excellent Excellent Very good Good

Surface arc resistance

Excellent Poor

Poor Good Good Poor Very poor Poor

Good Poor

Poor Very good -

Good

Excellent Excellent Excellent Excellent Very good Very good

Tracking resistance

Engineering Plastics

Perluoroalkoxyethylene

Styrene acrylamide copolymer ABS copolymer Acrylate-styreneacrylonitrile copolymer PTFE Polyvinyl luoride PVDF

PI PEI PU Urea-formaldehyde

18 13 5

GP GP 20% carbon ibre GP 18

13 14

GP GP

16 15 16 12

15

16

Glassreinforced GP GP GP GP

Nylon 6,10

15

14 14 14 15 14 17

14 15 15

GP

GP

Nylon 6,6

Nylon 6 Nylon 6,9 Nylon 11 Nylon 12 Nylon 6,12 PAI

GP GP Glassreinforced GP GP GP GP GP GP

Nylon-acrylonitrile alloy Nylon 6,6 Nylon 6,10

45

45 20 N/R

14 22

25

22 24 22 17

17

25

25 19 20 60 20 23

17 25 17

2.1

2.1 8 N/R

3.3 3.2

3

3.6 3.15 3.5 7

3.8

8

8 3.2 4.0 3.6 3.6 3.5

4.5 8 3.8

0.0002

0.0001 0.5 N/R

0.006 0.025

0.01

0.001 0.0013 0.008 0.04

0.15

0.2

0.2 0.02 0.05 0.05 0.02 0.01

0.05 0.2 0.015

Excellent

Excellent Very poor N/R

Poor

Good

Poor Very good Good Good

Good

Poor

Poor Poor Good Good Poor Very poor

Very poor Poor Good

-

Excellent Good N/R

Very poor

Poor

Poor Poor Good Good

Poor

Very good Poor Very good Poor Poor Very poor

Good Poor

Electrical Properties of Polymers

95

96 14 28

16.7 16. 15.8

14 18

GP GP

50

16 17.5 15

18

GP

40

14 30 13

15

GP

28

14 13 15.3

16

GP

GP GP Glassibre and bead reinforced Polysulfone GP PES GP Silicones GP ABS: Acrylonitrile-butadiene-styrene EVA: Ethylene-vinyl-acetate LDPE: Low-density polyethylene GP: General purpose N/R: Not reported PMMA: Polymethyl methacrylate PPO: Polyphenylene oxide PTFE: Polytetraluoroethylene PU: Polyurethane PVC: Polyvinyl chloride PVDF: Polyvinylidine luoride Source: Author’s own iles

Ethylene-tetraluoroethylene copolymer Ethylenechlorotriluoroethylene copolymer Fluorinated ethylenepropylene copolymer Chlorinated PVC Ultra-high molecular weight polyether Unplasticised PVC Plasticised PVC PPS

3.1 3.5 2.9

3.1 5 4.6

3.1 2.3

2.1

2.6

2.6

0.001 0.0021 0.001

0.025 0.06 0.017

0.02 0.0002

0.002

0.002

0.0008

Good Very poor Very good

Very poor Poor Very good

Good Very Good

Very good

-

Very poor

Poor Poor Excellent

Poor Poor Poor

Poor Excellent

Good

-

Very good

Engineering Plastics

Electrical Properties of Polymers

4.1.3 Volume Resistivity (ohm.m; Ω.m) The volume resistivity of a material is its resistance to the low of electrical current. Speciically it is the ratio of the potential gradient in the direction of the current to the current density. It is dependent upon moisture content and temperature and the values given in Table 4.3 are typical room temperature values.

4.1.4 Dissipation Factor The dissipation factor or (dielectric loss) is a measure of the loss rate of energy of a mode of oscillation in a dissipative system. A low dissipation factor implies eficient electrical insulation. The dissipation factor is deined as the ratio of in-phase power. It may also be deined as the tangent of the loss angle. It is frequency dependent. The lower the dissipation factor the more eficient the insulator system. Germer [1] has discussed the increasing use of PEEK for miniature electronics. Some examples of these are electrolytic capacitors, potentiomer components and microconnectors. He discusses the thermal, electrical and mechanical properties of this polymer and gives data on permittivity and dissipation factor and heat resistance.

4.1.5 Electrical Resistance and Resistivity Resistivity or speciic resistance (S) is deined as the electrical resistance (R) multiplied by the cross-sectional area of polymer test piece (A) and divided by its length (L):

S = R#A# 1 L

(4.1)

4.1.6 Surface Arc Resistance The arc resistance of a material is the time taken for the conductivity path to develop on the surface as the result of an arc passing between electrodes placed near the surface. Good arc resistance is necessary in conditions where high voltage discharges are unavoidable. Arc resistance is reduced by ire retardants. Arc resistance is highly

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Engineering Plastics dependent on the particular grade of material and this volume therefore ranks those materials that are inherently good or inherently poor. The advice of the raw material supplier should be sought to determine the optimum grade of any material.

4.1.7 Tracking Resistance The ability of an insulator to withstand surface discharge of electricity, tracking resistance is the electrical potential applied between two electrodes placed in contact with the surface that causes a conductive path to develop between them. Good tracking resistance is necessary in applications where surface contamination and degradation are unavoidable, for example in marine environments. Tracking resistance is highly dependent on the particular grade of material. Hazel [2] has discussed the phenomena of tracking and arcing in plastics used in electrical applications. He states that electrical tension may cause a tracking current to low on plastic surfaces, especially if they are contaminated with humidity, dirt or chemicals, and irregular interruptions can occur along this current path, which may be caused by evaporating liquids. At these points, small arcs are generated, whose thermo-mechanical effect erodes the material’s surface. Tracking resistance indicates how well the surface of a plastic material resists damage caused this way. Tracking resistance, or proof tracking index (PTI), measured according to the International Electrotechnical Commission TC112 [3], is the numerical value of the maximum test voltage at which there is no tracking between two electrodes while a test luid is dripped onto the surface. Arc resistance is closely connected with tracking resistance. Under the inluence of an arc (which in practice may be generated by a short circuit) the plastic should not form a conductive bridge and should, if possible vaporise, so as to extinguish the arc. Similarly, a glow-wire simulates a source of ignition. The glow-wire test according to VDE 0471-2-10 [4] provides information about whether an object, such as an overheating conductor, could be a ire hazard in an electrical apparatus. Dielectric properties must be taken into account when working in AC and highfrequency applications, such as data processing and information technology. They are important because the charges and dipoles of a plastic material change orientation in time with the cycles of the AC. This has two results, irstly, the electric ield strength is greater in the plastic than in the vacuum. The dielectric constant describes this parameter, whose value is mostly between 2.5−4, and may rise to 8−10 in conditioned Nylon. Secondly, the change of orientation requires energy: the dielectric loss factor

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Electrical Properties of Polymers describes this material feature, which with many engineering plastics, lies in the range of 0.1−1.10-3 but whose value varies with frequency, temperature and humidity content.

4.2 Typical Electrical Properties of a Range of Engineering Polymers It can be seen in Table 4.3 that electrical properties cover a wide range and thus the volume resistivity of various polymers is between 2 ohm.cm for epoxy resins to 10 ohm.cm for fluorinated ethylene-propylene copolymer. Similarly, dielectric strength is in the range from 12 mV/m for urea-formaldehyde resins to 55 mV/m for fluorinated ethylene-propylene copolymer and 60 mV/m for PA 12.

4.3 Effect of Reinforcing Agents on Electrical Properties For some electrical applications improvements in mechanical properties such as tensile strength of the polymer might be required, for example, impact resistant electrical plugs or housings for electrical gears. This can often be achieved by the incorporation of a reinforcing agent in the polymer formulation. Unreinforced PEEK, for example, has the electrical properties shown in Table 4.4.

Table 4.4 Electrical properties of PEEK Property Volume resistivity Dielectric strength Dielectric constant at 1 kHz Surface arcing resistance Tracking resistance Dissipation factor at 1 kHz

Value 16 ohm.cm 19 mV/m 3.2 Very good Good 0.0016

This makes the polymer very suitable for printed circuit board manufacture. However, the incorporation of 30% glass fibre into the PEEK formulation produces a pronounced improvement in tensile properties and flexural properties with some deviation in elongation properties as shown in Table 4.5.

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Table 4.5 Effect of glass fibre on mechanical properties of PEEK Properties Tensile strength (MPa) Flexural strength (GPa) Elongation of break (%) Strain at yield (%) Izod impact strength (kJ/m) Source: Author’s own iles

Unreinforced polymer 92 3.7 50 4.3 0.083

Reinforced polymer 151 10.3 2.2 0.09

Similar comments will apply, for example, to PES and PA 12, which have dielectric strengths of 16 and 60 mV/m, respectively. For PES the incorporation of 30% carbon ibre almost doubles the impact strength from 86 to 195 MPa and increases the lexural strength from 2.6 to 15.2%.

4.4 Applications of High Dielectric Strength Polymers In Table 4.6 the polymers are grouped in ranges of increasing dielectric strength. The polymers with the highest dielectric strengths between 30−70 mV/cm have been used in a range of critical applications as listed in Table 4.7. It is seen that these polymers, which also have excellent arcing properties, are used in the most critical electrical applications such as connectors, high temperature insulations, cable coverings, switch components and electronic components. This is to be contrasted with polymers having a low dielectric strength, which are used in much less critical applications.

Table 4.6 Comparison of dielectric strengths, dielectric content and resistance to arcing Polymer

PP Polyesters PEEK Polydiallylisophthalate Polydiallylphthalate Polyarylates

100

Dielectric strength Dielectric constant Arcing (mV/m) at 1 kHz resistance Dielectric Strength Range 10−20 mV/m 18 2.6 Excellent 13 5.0 19 3.2 Very good 14 4.1 Excellent 16 4.4 Very good 15 3.1 -

Tracking resistance Excellent Good Excellent Very good -

Electrical Properties of Polymers PC Alkyd resins Phenol formaldehyde Styrene-maleic anhydride PMMA PA 6,10 PA 6,9 Urea-formaldehyde Phenylene sulide Polysulfone PES Silicones

20 13 12 12

3.2 6.1 8 2.5

Very poor Very good Very poor Poor

Poor Very good Poor Poor

18 3.3 Excellent 17 3.8 Good 19 3.2 Poor 17 7 Good 13 4.6 Very good 16.1 3.1 Good 16 3.5 Very poor 15.8 2.9 Very good Dielectric strength range 20−30 mV/m 28 2.3 Very good

Excellent Poor Poor Good Poor Poor Poor Excellent

Excellent Good Good Very good Very poor Poor

Ethylene propylene Plasticised PVC

22 2.3 Excellent 28 2.1 Very good 26 2.5 Good 25 8 Poor 22 3.5 Very poor 24 3.1 Good Dielectric strength range 30−40 mV/m 30 2.3 Good 30 5 Poor

EVA

27

Poor

Ultra-high molecular weight polyethylene HDPE Polymethypentene Styrene-ethylene-styrene Nylon 6,11 PAI PEI

2.9 Poor Dielectric strength range 40−60 mV/m PET 40 3.5 Excellent Perluoroalkoxyethylene 45 2.1 Excellent Ethylene 40 2.6 Excellent trichloroluoroethylene PTFE

45

Fluorinated ethylene 50 propylene PA12 64 Polyoxymethylene 69 copolymer LDPE: Low-density polyethylene

Very good

Very good Poor

Poor Excellent

2.1

Excellent

Excellent

2.1

Very good

Good

3.6 3.7

Good Poor

Very good

Source: Author’s own iles

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Table 4.7 Applications of high dielectric strength polymers Polymer Perluoroalkoxyethylene PET Ethylene trichloroluoroethylene PTFE

Fluorinated ethylene propylene

Dielectric strength (mV/m) 45 40

Arc resistance Excellent Excellent

Tracking resistance Poor

40

-

-

45

Excellent

Excellent

50

PA 12 64 Polyoxymethylene 69 Source: Author’s own iles

Typical applications Insulation Electrical connections and terminal blocks Cable insulation

High temperature insulations and electronic relays Very good Good Terminal blocks, wire insulation and electronic components Good Electrical components Poor Very good Switch components

As an example, consider the selection of a suitable plastic for use in the fabrication of an electrical component, which has a dielectric strength exceeding 40 mV/m and a tensile strength above 50 MPa. It is seen in Table 4.8 that PET, PA 12 and polyoxymethylene all meet these requirements.

Table 4.8 Selection of polymers with high dielectric strength and tensile strength Polymer Perluoroalkoxyethylene PET Trichloroluoroethylene PTFE Fluorinated ethylene propylene PA 12 Polyoxymethylene Source: Author’s own iles

102

Dielectric strength (mV/m) 45 40 40 45 50 64 69

Tensile strength (MPa) 29 55 30 25 14 50 50

Good -

250 120 180

180 170 175

200 High 170 180 150 190

Thermal stability

17 15 15 16 17.5 16 15

14 2 16

16.7 15 13

21 60 24 22 16 16.7 13

16 28

19 20 14

Volume resistivity Dielectric (ohm.cm) strength (mV/m)

2.6 3.6 3.1 3.6 3.6 3.1 2.1 4.6

4.4 2.1

3.2 3.2 4.1

Dielectric constant (1 kHz)

Table 4.9 Outstanding thermal and electrical properties

Thermal properties Mould Continuous use shrinkage temperature (°C)

PEEK Good PBT Diallyl isophthalate Diallyl phthalate Epoxy resin Low Polymethyl pentene PPO PA 6 PA 12 PEI PI and PAI PES PSU PTFE PPS Source: Author’s own iles

Polymer

Poor Good Good Poor Poor Good Excellent Good

Very good Poor Good

Good Good Very good

Arc resistance

Poor Poor Poor Poor Poor Poor Excellent Poor

Very good Poor Good

Good Good Very good

Tracking resistance

Electrical Properties of Polymers

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Engineering Plastics Another combination of polymer properties that might be required is a good combination of electrical properties and thermal properties. An item, which operates at a high temperature would fall into this category. It is seen in Table 4.9 that three polymers, PEEK, PPS and PTFE meet the requirements of high continuous use temperature (250−180 °C), high dielectric strength (19−45 mV/m), high dielectric constant (2.1−4.6 at 1 kHz) high arc resistance (good to excellent) and high tracking resistance (good to excellent).

4.5 Effect of Reinforcing Agents on Electrical and Mechanical Properties

4.5.1 Glass Fibre Reinforcement In general addition of 10−60% glass fibre causes an improvement in the dissipation factor in PC and PA 6,6, and in surface arc resistance in PPO and epoxy resins but causes deterioration of dielectric constant in PA 6,6 and in tracking resistance of PP epoxies and phenylene oxide. Glass fibre caused an improvement in the dielectric strength of epoxies. Li and co-workers [5] investigated the effect on volume resistivity and percolation thresholds of the glass fibre and epoxy content of carbon black filled PP, PP/epoxy and PP/epoxy/glass fibre composites. The morphology of these conductive polymer composites was studied with scanning electron microscopy. The PP/epoxy/glass fibre/ carbon black composite exhibited a reduced percolation threshold when compared to that of the other composites. At a given carbon black content, the PP/epoxy/glass fibre/carbon black composite had a lower volume resistivity than the PP/carbon black and PP/epoxy/carbon black composites. The decreased percolation threshold and volume resistivity indicated that conductive paths existed in the PP/epoxy/glass fibre/ carbon black composite. The conductive paths were probably formed through the interconnection of glass fibre. Appropriate amounts of glass fibre and epoxy should be used to decrease the volume resistivity and provide sufficient epoxy coating.

4.5.2 Silica Resin Reinforcement Suwanprateeb and Hatthapanit [6] compared the use of black rice husk ash based silica as a filler in epoxy resins used for embedding electrical and electronic devices to the use of two commercial fillers, fused silica and crystalline silica, at different weight fractions between 20−60%. Increased mixing viscosity, thermal expansion

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Electrical Properties of Polymers and water absorption, with slightly lower tensile properties was observed, compared to commercial silica illers. It was suggested that the use of different combustion conditions for the rice husk ash, to lower the carbon content, may make the results more comparable.

4.5.3 Carbon Fibre Reinforced Plastics Only a limited amount of quantitative data is available on the electrical properties of 30% carbon ibre reinforced plastics as opposed to unreinforced plastics. Data for two such polymers are listed in Table 4.10.

Table 4.10 Effect of carbon fibre reinforcement on electrical properties Property PA 6,10 Dielectric constant at 1 kHz 4.8 (3.8) Dielectric strength (mV/m) 17 (17) Dissipation factor 1 kHz 0.015 Tracking resistance Poor Volume resistivity (ohm.cm) 12 (15) Very poor Data on virgin unreinforced polymer in parenthesis.

Epoxy resin 4.5 20 0.6 16

Source: Author’s own iles

In general, carbon ibres causes a deterioration of volume resistivity in epoxy resins or PTFE, and improves the dielectric strength and dielectric constant in epoxies but causes deterioration of surface arc resistance and tracking resistance in epoxies. PTFE causes deterioration in the dielectric constant and surface resistance in PA 6,6. Mineral illers also cause deterioration of the dielectric constant and surface arc resistance of PA 6,6.

4.5.4 Carbon Nanotubes As shown in Table 4.11 carbon nanotubes have now been studied in various polymers as a means of improving their electrical properties.

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Engineering Plastics

Table 4.11 Use of carbon nanotubes in polymer technology Polymer HDPE [7] PP [8] Epoxy resins [9] PU [10] Poly-p-phenylene vinylene [11] PEEK [12] PC [13] PEI [14] Epoxy [14] PA [15] Polylactide [16] PLA [17] PLA: Polylactic acid

Electrical properties studied Electrical conductivity Electrical Electrical resistivity Electrical conductivity Electrical conductivity Electrical conductivity Electrical properties Electrical properties Electrical properties Electrical conductivity Electrical properties Electrical conductivity

Source: Author’s own iles

Other substances, which have been used to modify the electrical properties of polymers include clay [18], carbon block [19], graphite [20], bentonite [21], carbon ibre [22], silica [23, 24] and montmorillonite [25].

4.5.5 Carbon Black and Carbon Fibre Tantawy and co-workers [26] investigated the effect of Joule heating on the electrical and thermal properties of conductive epoxy resin-carbon black composites. The Joule heating effect was shown to be an effective and promising method for enhancing the electrical and thermal stabilities of epoxy resin-carbon black composites for consumer use as heaters and in other electronic areas, such as effective electromagnetic shielding. Ying and co-workers [27] demonstrated very low electrical conductivity properties of PP/carbon black composites. Zhou and co-workers [28] measured the electrical conductivity/resistivity of carbon black illed linear low-density polyethylene (LLDPE) and blends of LLDPE with ethylene-methylacrylate (EMA). The percolation threshold of the blended polymer composite was signiicantly lower than that of the LLDPE composite, although in an EMA composite the threshold is higher. This effect was due to preferential absorption of the carbon black into the LLDPE due to phase separation and immiscibility in low-density polyethylene (LDPE)/EMA blends. The viscosity of polymers in the blend

106

Electrical Properties of Polymers appeared to determine distribution of the carbon black, indicating that choice of polymer viscosity could be used to control carbon black distribution. Çakmak and co-workers [29] used electrochemical synthesis to produce carbon ibre reinforced polydimethylsiloxane (PDMS)-polypyrrole (PPY) composites of various compositions using aqueous p-toluenesulfonic acid as an electrolyte. The composites obtained were characterised by thermal gravimetric analysis, SEM, conductivity measurements and mechanical tests. Conductivities of the composites were observed to be in the range of 2.2–4.0 S/cm. SEM studies showed that the carbon ibres were coated uniformly by PDMS/PPy matrix. In mechanical tests, the tensile strength of the composites increased with increasing carbon ibre content. A higher percentage elongation was achieved by the addition of PDMS. Highly lexible, foldable and mechanically strong conductive composites were obtained.

4.6 Electrical Properties

4.6.1 Dielectric Strength Cruz and Zanin [30] determined the dielectric strength of blends of virgin HDPE and up to 100% recycled HDPE. Introduction of the recycled polymer reduced the dielectric strengths by up to 17% because of the metallic impurities in the recycled polymer. Ramar and Alagar [31] compared the dielectric strengths of nanoclay reinforced blends of ethylene-propylene-diene monomer grafted with tris(2-methoxyethoxy)vinylsilane (EPDM-g-TMEVS) and EPDM-g-TMEVS/PMMA blends. The values of dielectric strength, volume resistivity, surface resistivity and arc resistance were all increased with increasing concentration of EPDM-g-TMEVS because of the presence of Si-OSi linkages. The blends illed with nanoclay showed improved dielectric properties because of the presence of the inorganic moiety.

4.6.2 Volume Resistivity Nedjar [32] has reported on the measurement of volume resistivity of crosslinked polyethylene (XLPE) grades used in high voltage cables and the effect of thermal aging on the electrical properties of the cable. Volume resistivity measurements have been reported on epoxy resin-polyaniline (PANI) blends resulting in the establishment of a correlation between a shoulder in

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Engineering Plastics the 1585 cm–1 band and the degree of volume sensitivity [33]. Naik and Mishra [34] found that the surface resistivity of natural ibre HDPE composites decreased with an increase in the natural ibre iller content in the composites, whilst the volume resistivity increased. Nishikawa and co-workers [35] investigated the electrical properties of a resin prepared with ABS terpolymer and crushed carbon ibre reinforced plastics. The resin was prepared by injection moulding. The electrical resistivity of the composites showed a percolation type of conduction behavior Measurement of alternating current impedance revealed that the conduction mechanism was attributed to the direct conductive paths generated by distributed carbon ibres, however, a strong frequency dependence of the impedance was observed for the carbon ibre reinforced plastic content near the critical one. The frequency dependence of the impedance was caused by the inter-iber connection and could be expressed as a simple equivalent circuit. The absorption component of the shielding effect was smaller than the expected value estimated from its resistivity. The decline of the shielding effect is thought to be caused by the decrease in effective thickness because of the ibre orientation. Gao and Zhao [36] investigated the resistivity of elastic gels based on gelatine containing starch particles. This research aimed to improve the stability of geometrical shape, mechanical performance, and particle dispersion of electrorheological hydrous elastomers. Gelatin water-based elastic gels containing starch particles were prepared under an applied DC electric ield, and their electrorheological effects were described using compression modulus and electrical resistivity. The results demonstrated that the mechanical and electrical properties of the electrorheological elastomers were dominated by an externally applied electric ield as well as the weight fraction of particles. The elastomer studied has a steady geometrical shape and mechanical performance because of the addition of glycerin into the matrix, and has a better dispersion of particles. Volume resistivities have been reported on phenol-formaldehyde [37], carbon ibre reinforced ABS terpolymer [35], natural rubber [38], polystyrene (PS) [35], HDPEnatural ibre composites [34], carbon black illed PP-epoxy-glass ibre composites [5], XLPE [32], nanoclay reinforced EPDM-g-TMEVS [31] and epoxy resin/PANI blends [33].

4.6.3 Dielectric Constant Tsuchiya and co-workers [39] discussed the dielectric properties of polybinaphthylene ether, which demonstrated particularly good insulating properties.

108

Electrical Properties of Polymers Dielectric constants have been reported for several polymers including PI [40-42], epoxy resins [43], PU [43], XLPE-PE [44], LDPE-zinc oxide nanocomposites [45], PANI nanoibres [46], doped polyimines derived from selenophene [40], PI-zirconium propoxide nanocomposites [47] and PANI-cerium oxide composites [48]. Insulating materials possess a dielectric constant (εʹ) characterising the extent of electrical polarisation that can be introduced in the material by an electric ield. If an alternating electric ield is applied, the polarisation lags behind the ield by a phase angle, δ. This results in partial dissipation of stored energy. The dissipation energy is proportional to the dielectric loss (εʹʹ) and the stored energy is proportional to the dielectric constant (εʹ) permittivity. The dielectric thermal analysis technique normally obtains data from thermal scans at constant impressed frequency. The glass transition temperature at which molecular motions become faster than the impressed timescale are recorded as peaks in εʹʹ and tan δ. It is a simple matter to multiplex frequencies over the whole frequency range of 20−100 kHz and under such conditions the peaks in εʹʹ are shifted to higher temperatures as the frequency is increased. A further option allows data to be obtained in the frequency plane under isothermal conditions. This technique is used principally for the rheological characterisation of polymers and measurement of the dielectric constant. The technique measures changes in the properties of a polymer as it is subjected to a periodic electric field. This produces quantitative data, which can be used to determine the capacitive and conductive nature of a material. Molecular relaxations can be characterised and flow and cure of resins can be monitored. While the theory of dielectric analysis is well known, its use has not been possible due to lack of effective instrumentation. Modern dielectric thermal analyses make the technique a practical reality.

4.6.4 Tracking Resistance Research has been reported on Kevlar para-aramid fibres, which possess three times the tracking resistance of glass reinforced plastic flame retardant compounds [49].

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Engineering Plastics

4.6.5 Failure of Electrical Properties Fournier and Preux [50] review polymeric materials used in varnishes for the insulation of electrical wiring wires, with particular reference to PU formulations. Ezrin and Lavigne [51] discussed the failure of electrical insulations, particularly cable insulation, during manufacture or in service. Failure during manufacture may be due to low mechanical or electrical properties, or unacceptable appearance of either the insulation or the conductor. Discoloration associated with volatiles from the plastic, or from sulfur cured polymers is described. Service failures include electrical failure of XLPE underground power cable, due to the combined effects of water, oxygen and electrical energy, oxidative degradation catalysed by copper, degradation by agricultural fertilisers or degradation by minerals in the soil.

4.6.6 Electrical Conductivity Electrical conductivity measurements have been reported on a wide range of polymers including carbon nanoibre reinforced HDPE [52], carbon black illed LDPE-ethylene methyl acrylate composites [28], carbon black illed HDPE [53], carbon black reinforced PP [27], talc illed PP [54], copper particle modiied epoxy resins [55], epoxy and epoxy-haematite nanorod composites [56], polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA) blends [57], polyacrylonitrile based carbon ibre/PC composites [58], PC/MnCl2 composite ilms [59], titanocene polyester derivatives of terephthalic acid [60], lithium triluoromethane sulfonamide doped PS-blockpolyethylene oxide (PEO) copolymers [61], boron containing PVA derived ceramic organic semiconductors [62], sodium lanthanum tetraluoride complexed with PEO [63], PC, acrylonitrile butadiene [64], blends of polyethylene dioxythiophene/ polystyrene sulfonate, PVC and PEO [65], EVA copolymer/carbon ibre conductive composites [66], carbon nanoibre modiied thermotropic liquid crystalline polymers [67], PPY [68], PPY/PP/montmorillonite composites [69], carbon ibre reinforced PDMS-PPY composites [29], PANI [70], epoxy resin/PANI dodecylbenzene sulfonic acid blends [71], PANI/PA 6,6 composites [72], carbon ibre EVA composites [66], HDPE carbon ibre nanocomposites [52] and PPS [73].

4.6.7 Electrical Resistance Electrical resistance measurements have been reported on PANI/cerium oxide composites [48], polyester ibres and carbon containing epoxy composites [74].

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Electrical Properties of Polymers Electrical resistivity has been measured on reinforced ABS terpolymers [75], jute illed phenol-formaldehyde resins [37] and carbon black PP composites [72].

4.7 Electrically Conducting Polymers

4.7.1 Polyaniline Polyaniline is a relatively recent development. Electronically conducting polymers have applications in the ield of electronics, micro-electric devices, computers, photographic equipment and, as discussed next, in developments such as electrically conducting electrochemical and fuel cells. Charge transport in electrically conducting polymers (ECP) is related to the role of easily polarisable delocalised p-electrons, which determines the electrical properties of conducting polymers [75]. Changes in molecular structure due to the localisation of p-electrons and electronic repulsion between the polycations inluence the operation of a conducting polymer micro-acutator [76]. The electrical conductivity properties of PANI make it probably the most frequently discussed ECP. Developments of this polymer are discussed next in date order [77-80]. Furukawa and co-workers [81] state that PANI is an interesting material because it is not only an ECP but is also a good material to use as an electrode of a secondary battery with aqueous or non-aqueous electrolytes. PANI polymerised from aniline in an aqueous acid solution is converted to several forms with different electrical properties by acid/base treatments and oxidation/reduction. The as-polymerised form gives high electrical conductivity (~5 S/cm). It becomes insulating when treated with an aqueous alkaline solution or is reduced electrochemically in an aqueous acid solution. Reduced-alkali-treated PANI is also insulating and is unstable in air; its colour changes from white to blue upon exposure to air. PANI doped with electrolyte anions is obtained by electrochemical oxidation [82]. It was found in this work to be a new conductivity form (σ = 5.8 S/cm). Recently, a secondary lithium battery with a reduced alkali pellet as the cathode, and non-aqueous electrolytes has been developed as a power source of memory back up and a maintenance-free power source combined with a solar battery. Furukawa and co-workers [81] elucidated the structure of each of these forms of PANI. Reduced alkali treated PANI was identiied as polyimino-1,4-phenylene [–(NHC6H4)n–)]. Acid treated, electrically reduced PANI is an imino-1,4-polyphenylene unit (–NHC2H4–) and its salt unit is [–NH2+A–C6H4– (A- anion)].

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Engineering Plastics Treatment of reduced alkali treated poly-PANI/[polyimino-1,4-polyphenylene (NHC6H4)] with oxygen converts part of the consecutive –NHC6H4NHC6H4– units to a nitrilo-2,5-cyclohexadiene-1,4-diylidenenitrilo-1,4-phenylene unit (–N=C6H4=NC6H4–). Semiquinone radical cations of –NHC6H4NHC6H4– units exist only in the conducting forms of PANI as polymerised and reduced alkali treated PANI indicating that the semiquinone radical cation plays an important role in the electrical conduction of PANI. The polymerised form of PANI referred to previously consists of a hybrid of the imino-1,4-phenylene unit (–NHC6H4–) and nitrilo-2,5-cyclohexadiene1,4-diylidenenitrilo-1,4-phenylene unit (–N=C6H4=NC6H4–) containing a quinone diimine structure (–N=C6 H4=N–). Rao and co-workers [82] used an inverted emulsion process for the synthesis of the emeraldine salt of PANI using a novel oxidising agent, benzoyl peroxide. The polymerisation was carried out in a non-polar solvent in the presence of four different protonic acids as dopants and an emulsiier (sodium lauryl sulfate). The polymer salts were characterised spectroscopically by ultraviolet-visible, Fourier-transform infrared, Fourier-transform Raman and electron paramagnetic resonance spectroscopy. Thermogravimetric analysis, was used to determine the stability of the salts and the activation energy for the degradation. The conductivity of the salts was found to be in the order of 10–1 S/cm. The conductivity values of the PANI salts measured as pellets are given in Table 4.12. The conductivity of the PANI salts are in the range of 0.3−0.9 S/cm. The higher conductivity of PANI obtained by the inverted emulsion method could be due to a more homogenous protonation of the imine nitrogen and a more ordered chain conformation of the polymer. The conductivity of the PANI-camphor sulfonic acid was found to be higher than the other salts (see Table 4.12).

Table 4.12 Conductivity and EPR data for PANI Salts Sample

Conductivity Spin concentration g value A/B ∆H (G) (× 10–1 S/cm) (spins g–1) PANI-H2SO4 2.95 1.3520 × 1019 2.0037 1.02 3.25 PANI-benzoyl peroxide 7.11 2.8789 × 1019 2.0019 1.00 3.50 PANI-camphor sulfonic acid salt 9.04 2.1478 × 1019 2.0029 1.00 3.25 PANI-p-toluene sulfonic acid salt 7.71 2.9041 × 1018 2.20025 1.06 2.75 PANI: Polyaniline A/B: Peak ratio AH (G): Heat of reaction Reproduced with permission from P.S. Rao, S. Subrahmanya and D.N. Sathyanarayana, Synthetic Metals, 2002, 128, 3, 311. ©2002, Elsevier [87]

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Electrical Properties of Polymers Rao and co-workers [82] reviewed several ways of synthesising PANI using electrochemical and chemical oxidative polymerisations. Oxidising agents that have been studied include ammonium persulfate, potassium dichromate, ferric chloride, potassium permanganate, potassium bromate, potassium chlorate [83], tetrabutyl ammonium phosphate [84] and hydrogen peroxide [85]. Emulsion polymerisation methods have several advantages, including [86-90]: •  High molecular weight polymers can be made at fast polymerisation rates. •  The continuous water phase is an excellent conductor of heat, which is used to  remove water from the system and this can increase the rate of reaction for may methods. •  The inal products can be used as is and does not usually need to be altered or  processed. Ruckenstein and Sun [89] have used inverted emulsion polymerisation for the synthesis of PANI rubber composites using an isooctane-toluene mixture and water to form the emulsion and using ammonium persulfate as the oxidant. Inverse emulsion polymerisation consists of an aqueous solution of the monomer, which is emulsiied in a non-polar organic solvent and the polymerisation is initiated with an oil-soluble initiator. The reaction is carried out in a heterogeneous system in which the reaction takes place in a large number of reaction loci dispersed in a continuous external phase. Tsotra and Friedrich [71] measured the electrical conductivity of epoxy resin/PANIdodecylbenzene sulfonic acid blends and found that the electrical conductivity increases with the addition of 10% of PANI dodecylbenzene sulfonic acid reaching a value higher than 10-7 S/cm. Tsotra and co-workers [33] showed that when blends of epoxy resin and PANI are doped with dodecylbenzene sulfonic acid and cured with various acidic and alkaline hardeners such as amine, imidazole, anhydride and boron triluoride a relationship is developed between the shoulder at the 1,585 cm-1 band in the spectral region 1,575−1,560 cm–1 with the degree of volume resistivity developed. Parvatikar and co-workers [48] measured the electrical resistance of PANI/cerium oxide composites and the change in this with relative humidity. The results showed that there was potential for these composites to be used as humidity sensors.

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4.7.2 Carbon Nanotubes A recent development in the production of ECP is based on the incorporation of carbon nanotubes and other substances in the polymer formulation. Work on the development of carbon nanotube based ECP and the theory behind their use is reviewed next. Fan and co-workers [91] used in situ polymerisation of pyrrole on to carbon nanotubes to produce carbon nanotube-pyrrole composites and showed that the electrical conductivity of the composites at room temperature was higher than that of pure PPY. Pure polypyrrol, carbon nanotubes and the nanocomposites all exhibited semiconductive behaviour. Polymers studied included HDPE [92], PP [93], epoxy resin [94], PU [95], PLA [96], poly-p-phenylene vinyl ether [97], PEEK [98], PC [99], PEI [100], polylactide [101] and PI [102].

4.7.3 Metal containing Electrically Conductive Polymers Bandara [103] has described the use of conducting polymers as additives enabling insulating polymers to form electrically conducting plastics or composites. In the frequency range 30 MHz to 1 GHz, electromagnetic emissions are a major concern, as they cause interference in broadcast communications. The most common method of isolating electromagnetic radiation is to attenuate the signal at the device’s structural housing. This is commonly achieved by fabricating the housing with conductive materials, which usually contain conductive metal illers of either a particulate or ibrous nature. However, attractive features of the plastics host material such as low density, corrosion resistance and ease of formation of complex housing shapes are lost or reduced when metallic illers are introduced. The introduction of metal illers into polymers to produce conducting polymer composites has stimulated interest in a different strategy: the use of ECP as the conductive component in composite materials. A similar and related requirement exists for anti-static materials. Anti-static agents are substances used to reduce the tendency of polymeric products to acquire or maintain a surface charge. The build-up of surface charge can often result in a spark discharge, which can be hazardous. Aspects covered in this paper include the effect of interaction between iller particles and host matrix, network formation between iller particles, and conductive composites and their applications. Lin and Chiu [55] studied the effects of silver or copper particle composition (silver coated or uncoated copper), on particle shape (lake or spherical), particle size and oxidation temperature on the electrical properties of copper-illed epoxy resin electrically conductive adhesives. They also studied pressure dependent conduction behaviour of compressed copper particles. The silver-coated copper particles showed signiicantly greater oxidation resistance than un-coated copper particles because the

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Electrical Properties of Polymers silver coating provides good oxidation resistance at temperatures lower than 175 °C. The electrically conductive adhesives illed with lake-shaped copper particles offered better electrical conduction than those illed with spherical copper particles. Pourabas and Peyghambardoost [53] showed that copper illed epoxy resin composite had electrical conductivity properties. Afzal and co-workers [104] studied the electrical properties of PANI/silver nanocomposites. The silver nanoparticles in PANI reduced the charge trapping centres and increased the conducting channels of the polymer.

4.7.4 Other Conducting Polymers Many other types of ECP have been described. These include PS-block-PPO [61], boron containing PVA [62], polyethylene dioxythiophene/polystyrene sulfonate [65], PC-ABS composites [64], PEO composites [64], PEO complexes with sodium lanthanum tetraluoride [63], chlorine substituted PANI [70], PVP-PVA coupled with potassium bromate [57], PANI-PA 6,6 composite ilms [72], talc-PPY composites [54], epoxy resin alpha-haematite nanorod composites [56], PP-montmorillonite composites [69], magnetite containing polymers [105], LDPE [27], PC-acrylonitrilebutadiene composites [106], sodium ion conducting PEO complexed with sodium lanthanum tetraluoride [63], PVDF [107], PANI composites [108], PP novolac resins [109], dendrimers containing light switchable azobenzene [110], PVP/PVA [107] and PPY [111].

4.8 Fire Retardant Plastics for the Electrical Industry Because of the possible toxic effects of antimony and halogen containing ire retardant polymers in the event of an electrical ire, efforts are now being made to produce ire retardant plastics for the electrical industry, which do not contain these types of ire retardants. Red phosphorus containing PA 6,6 has an excellent performance for lame retardence, electrical insulating properties, heat aging behaviours, toughness and rigidity [112]. This polymer has been used in the construction of circuit breakers, terminal blocks and switches. Organophosphorus, or organic nitrogen compounds can also be used in these applications but are more expensive.

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Miscellaneous Polymer Properties

5.1 Abrasion Resistance and Wear Wear is deined as the damage to a solid surface, generally involving progressive loss of material, due to relative motion between that surface and a contacting substance or substances. The mechanisms of wear are abrasion, adhesion, erosion, fatigue and fretting. Abrasive wear has a contribution of at least 60% of the total cost due to wear [1]. Abrasive wear is caused by hard particles that are forced and moved along a solid surface [2]. In design there are two main characteristics, which make use of polymers and reinforced polymers attractive compared to use of conventional metallic materials. Such polymers have a relatively low density and reliable tailoring capability to provide the required strength and stiffness. In fact abrasion involves the tearing away of small pieces of material, therefore the tensile strength, fatigue life and hardness are important factors in determining the wear characteristics of a polymer. However, there is a need to understand the basic phenomenon of two and three body abrasion tests [3-7] and the movement pattern of the dry and loose abrasive particles [8]. The abrasive wear of polymers is the subject of quite a lot of literature. In the past much research has been carried out on the abrasive wear mechanism of polymers in general and polymer composites in particular [9-13]. Most test programmes have used two body abrasion tests. In a review of some of the literature concerning abrasive wear of polymers, Evans and Lancester [14] tested about 18 polymers: low-density polyethylene (LDPE) exhibited the lowest wear rate in abrasion against a rough mild steel but the highest wear rate was for abrasion with coarse corundum paper. Shipway and Nago [15] investigated the abrasive behaviour of polymeric materials at a micro-scale level. They concluded that the wear behaviour and wear rates of the polymers critically depended on the polymer type. Furthermore, the wear was associated with indentation type morphology in the wear scar and low values of tensile strain to failure. Harsha and Tewari [3] investigated the abrasive wear behaviour of polyaryl ether ketone and its composites against silicon carbide (SiC) abrasive paper. They concluded that the sliding distance, load and abrasive grit size all have a signiicant inluence on abrasive wear performance.

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Engineering Plastics Liu and co-workers [16] investigated the wear behaviour of ultra-high molecular weight polyethylene (UHMWPE) polymer. They concluded that the applied load is the main parameter and the wear resistance improvement of iller reinforced UHMWPE was attributed to the combination of hard particles, which prevent the formation of deep, wide and continuous furrows. Bijwe and co-workers [17] and Xu and Mellor [18] tested polyamide 6 (PA), polytetraluoroethylene (PTFE) and their various composites in abrasive wear under dry and multi-pass conditions against SiC paper on a pin-on-disc tribometer. They concluded that the polymers without illers had better abrasive wear resistance than their composites. Rajesh and co-workers [19] studied the behaviour of PA 6,6. They concluded that the water absorption and thermal properties affected the morphology of PA, which in turn affected the tribological properties of PA. Furthermore, the speciic wear rates showed fairly good correlation with various mechanical properties such as ductility, fracture surface energy, tensile modulus and the time of failure under tensile stress. Rajesh and co-workers [20] also investigated the inluence of illers on abrasive wear of a PA composite. They compared polymer composite wear with the wear of the unilled polymer. They evaluated the results by using tensile strength and elongation to break properties of the materials. Apart from experimental studies several models have also been proposed that attempt to relate the abrasive wear resistance of polymers to some mechanical properties of the material such as hardness and tensile strength. Ozel [21] studied the abrasive wear behaviour of liquid crystal polymer, 30% glass-reinforced PA 4,6 and 30% glass ibre reinforced polyphenylene sulide (PPS) engineering polymers under atmospheric conditions. Pin-on disc wear tests were carried out at 1 m/s test speed and load values of 4, 6 and 8 N. Test durations were for 50,100 and 150 m sliding distances. Emery paper grit varying from 70−400 grit was used as an abrasive disc surface. After each test the mass loss of the pin was recorded. Finally the specific wear rates were calculated from the wear volume of the pin for test duration distances of 50, 100 and 150 m. The results showed that the highest wear rate is for liquid crystal polymer with a value of 4.43 × 10-1 mm3/Nm and the lowest wear rate is for 30% glass-reinforced PA with a value of 1.63 × 10-2 mm3/Nm. Furthermore, for all materials the wear rate increased linearly with increasing duration distance and decreased with the increase in load value. Ozel [21] reached the following conclusions: •  The  speciic  wear  rate  for  liquid  crystal  polymers,  30%  glass  ibre  reinforced  PA 4,6 and 30% glass fibre reinforced PPS increased with the increase in sliding resistance. •  The speciic wear rate for the liquid crystal polymer decreased with the increase 

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Miscellaneous Polymer Properties in load value while the speciic wear rate of 30% glass ibre reinforced PA 4,6 and 30% glass ibre reinforced PPS increased with the increase in load values. •  The wear rate of liquid crystal polymer, 30% glass ibre reinforced PA 4,6 and 30%  glass ibre reinforced PPS increased with the increase in abrasive grit resistance (lower grit). •  The highest wear rate is for liquid crystalline polymer and the lowest wear rate  is for 30% glass ibre reinforced PA 4,6. •  The speciic wear rates of liquid crystalline polymer, 30% glass ibre reinforced  PA 4,6 and 30% glass ibre reinforced PPS range from 3 × 10-2 to 4.43 × 10-1 mm3/Nm, 1.63 × 10-2 to 1.1 × 10-1 and 2.4 × 10-2 to 2.1 × 10-1 mm3/Nm, respectively. •  The speciic wear rate is inluenced by the mechanical properties of material such  as tensile strength x elongation to break value. The higher this value then the lower is the wear rate. Demir [22] studied the dry sliding wear behaviour of commercially available polyetherimide (PEI) containing 20% glass ibre reinforced composites and polysulfone (PSU) containing 20% glass ibre reinforced composites used in electrical contact breaker components using a pin-on-disc rig. The disc materials used were steel (Figure 5.1) and PA 4,6/30% glass ibre reinforced composites (Figure 5.2). Wear tests were conducted at 0.5 and 1.0 m/s sliding speeds and 20, 40 and 60 N load values and under atmospheric conditions of temperature and humidity. Different combinations of rubbing surfaces were examined and the dynamic friction coeficients and speciic wear rates determined and compared. Polymer pin worn surfaces were examined by optical microscopy and the wear mechanisms identiied as being a combination of adhesive and abrasive wear. For all material combinations, the coeficient of friction shows little sensitivity to sliding speed and applied load values and a large sensitivity to combinations of materials. For speciic wear rate, the PEI composite showed little sensitivity to change in load, speed and materials combination, whereas PSU composites how a large sensitivity to the change in load and material combinations. The friction coeficient of 20% glass ibre reinforced PEI and 20% glass ibre reinforced PSU rubbing against a AISA 4140 steel disc was around 0.3 and was about 0.12 when rubbing against a 30% glass ibre reinforced PA 4,6. The speciic wear rates for PEI and PSU composites were in the order of 10-15 to 10-14 mm3/Nm. The wear mechanisms were a combination of abrasive and adhesive wear.

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Engineering Plastics 0,5 0,45 Friction coefficient

0,4 0,35 0,3 0,25 0,2 0,15 0,1 0,05

PSU+20%GFR v1=0,5 m/s PSU+20%GFR v2=1,0 m/s PEI+20%GFR v1=0,5 m/s PEI+20%GFR v2=1,0 m/s

0 20

40 Load (N)

60

Figure 5.1 Relationship between the friction coeficient and load of 20% glass ibre reinforced PEI and 20% glass ibre reinforced PSU ibre composites against AISI 4140 steel, at different sliding speeds. Reproduced with permission from Z. Demir, Journal of Polymer Engineering, 2009, 29, 8-9, 549. ©2009, De Gruyter Publishing [22]

0,5

PSU+20%GFR v1=0,5 m/s PSU+20%GFR v2=1,0 m/s PEI+20%GFR v1=0,5 m/s PEI+20%GFR v2=1,0 m/s

0,45 Friction coefficient

0,4 0,35 0,3 0,25 0,2 0,15 0,1 0,05 0 20

40 Load (N)

60

Figure 5.2 Relationship between friction coeficient and load of 20% glass ibre reinforced PSU composites and 20% glass ibre reinforced PEI composites against a 30% glass ibre reinforced PA 4,6 composite of different sliding speeds. Reproduced with permission from Z. Demir, Journal of Polymer Engineering, 2009, 29, 8-9, 549. ©2009, De Gruyter Publishing [22]

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Miscellaneous Polymer Properties Table 5.1 shows fatigue index, abrasion resistance and coeficient of friction for a range of polymers. This information is useful when combined with the major mechanical requirements of the polymer in reaching a decision on any compromises that need to be made when choosing a polymer that is suitable for a particular application. Polymers, which for example, have a combination of a very good category for all three characteristics include high-density polyethylene (HDPE), polypropylene (PP), various PA, PTFE and polyvinylidine luoride, polyurethane (PU) and perluoroalkoxyethylene.

Table 5.1 Comparison of fatigue index, abrasion and coefficieint and friction for a range of polymers Polymer

Fatigue index

LDPE XLPE HDPE PP Polybutylene Polymethyl pentene Ethylene-propylene copolymer Epoxy resins Acetate copolymer Polyesters Polybutylene terephthalate PET PEEK PE PC PPO ABS terpolymer (30% glass ibre) Phenol-formaldehyde Perluoroalkoxyethylene Styrene-maleic anhydride copolymer PMMA EVA copolymer PA 11 PA 12 PA 6,6 PA 6,10 PA 6

Very good Good Very good Excellent Very good Very good Excellent Poor Very good Good Good Poor Very good Good Poor Very poor Poor Poor Very good Poor Poor Very good Very good Very good Very good Very good Very good

Abrasion or wear resistance Poor Good Good Good Very good Good Good Good Poor Good Good Good Poor Poor Very poor Poor Good Very poor Very poor Good Poor Good Good Good Good Good

Coefficient of friction Very poor Very poor Good Good Very poor Poor Very poor Very poor Very poor Poor Very poor Good Very poor Poor Good Very poor Very poor Poor Very poor Very poor Very poor Good Good Good Good Good

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Engineering Plastics PA 6,9 PA 6,12 PAI PI PEI PU Polyesteramide Styrene-acrylonitrile copolymer Acrylate-styrene-acrylonitrile terpolymer PTFE Polyvinyl luoride PVDF Perluorooxyethylene (20% glass ibre) Ethylene chlorotriluoroethylene (glass ibre) Fluorinated ethylene-propylene copolymer PPS (glass ibre) PES PSU (10% glass ibre) Silicones ABS: Acrylontrile-butadiene-styrene EVA: Ethylene-vinyl acetate PAI: Polyamide-imide PC: Polycarbonate PE: Polyethylene PEEK: Polyether ether ketone PES: Polyether sulfone PET: Polyethylene terephthalate PI: Polyimide PMMA: Polymethyl methacrylate PPO: Polyphenylene oxide PPS: Polyphenyl sulide XLPE: Crosslinked polyethylene Source: Author’s own iles

Very good Very good Good Poor Very poor Excellent Very good Very poor Very poor Very good Very good Excellent Good Very good Very good Poor Very poor Poor Poor

Good Good Very good Very good Poor Very good Very good Very poor Very poor Very good Poor Good Poor Poor Very poor Good Good Good Very good

Good Good Poor Good Poor Very good Very poor Very poor Very poor Excellent Good Very good Good Very good Poor Good Good Good Very good

5.2 Fatigue Index This is an assessment of the ability of materials to resist oscillating (or dynamic) load or delection controlled deformation. An excellent rating indicates excellent resistance to fatigue loading. A very poor rating indicates poor resistance to fatigue loading. ATS FAAR supply lexing machines for the measurement of resistance to dynamic

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Miscellaneous Polymer Properties fatigue to ASTM D430 [23] and ASTM D813 [24]. These test methods are utilised to test the resistance to dynamic fatigue of rubber-like materials when subjected to repeated bending. The tests stimulate the stresses either in tension or in compression of inlection or in a combination of the three modes of load application to which the materials will be subjected when in actual use. The failure of the tested specimens is indicated by cracking of the surface or as prescribed by ASTM D813 [24], by the dimensional increase of a nick made on the specimen before starting the test. In the case of composite materials the failure can show up as separation of the different layers. Lin and co-workers [25] also investigated the static tensile strength and fatigue behaviour of long glass ibre reinforced semi-crystalline PA 6,6 and amorphous PC composites. The static tensile measurement at various temperatures and tensiontension fatigue loading tests at various levels of stress amplitudes were studied. The two-parameters, Weibull distribution function and the pooled Weibull distribution function were applied to obtain the statistical probability distribution of experimental data of static tensile strength and fatigue life under different stress amplitude tests. The phenomenon of the increasing dynamic creep property and the temperature under tension-tension fatigue loading are compared between semi-crystalline and amorphous composites. Results show that the static tensile strength of PA composites is higher than that of PC composites, with lower fatigue life and more sensitivity to temperature. The slope of S-N0 curves of long glass ibre reinforced semi-crystalline PA and amorphous PC composites were found to be almost identical.

5.3 Coefficient of Friction This is an assessment of the coeficient of friction of material in terms of dynamic (sliding) friction against steel. It should be remembered that friction is inluenced by temperature, surface contamination and most importantly by the two material surfaces. An excellent rating indicates a low coeficient of friction (see Table 5.1). A very poor rating indicates a high coeficient of friction. Miyata and Yamaoka [26] used scanning probe microscopy (SPM) to determine the micro-scale friction force of a silicone-treated polymer ilm surface. PU acrylates cured by an electron beam were used as the polymer ilms. The micro-scale friction force obtained by SPM was compared with macro-scale data, such as surface free energy determined by the Owens-Wendt method and the macro-scale friction coeficient determined by the ASTM D1894 method [27]. These comparisons showed that a good linear relationship existed between the surface free energy and the friction force, which was insensitive to the nature of the polymer specimens or to the silicone

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Engineering Plastics treatment methods. Good linearity was also observed between the macro-scale and the micro-scale friction force. It was concluded that SPM could be a powerful tool in this ield of polymer science. Evrard and co-workers [28] reported coeficient of friction measurements for nitrile rubbers. Zsidai and co-workers [29] reported results of a series of test carried out to determine the friction properties of engineering plastics by the measurement of small and large test specimens on a steel and diamond-like carbon coating surface. The objective was to compare the friction properties of a surface provided with a diamond-like carbon coating with measurements obtained on a steel surface as a function of the engineering plastic used, and to examine the practical possibilities of the diamond-like coating. The plastics tested included PA, polyacetals and PET/PTFE. Taylor and Pollet [30] reported the results of a study of friction between fabrics used for clothes, including cotton, wool, polyester ibre and acrylic ibre, and aluminium, Formica and rubber under zero or low applied normal forces. The effects of various factors, such as surface roughness, directionality, nature of table surface, pressure and velocity, on frictional force are discussed and an empirical law proposed to model the dependence of friction on velocity. SPM initially provided three-dimensional visualisation of a surface down to the atomic scale using scanning tunnelling microscopy and atomic force microscopy (AFM). A range of imaging modes and spectroscopic techniques can be used to obtain additional information on the physical, chemical and thermal properties of polymeric materials, including surface friction and force modulation. A pulsed force mode enables both of these properties to be displayed simultaneously. Intermittent contact AFM (tapping mode) combined with phase imaging provides fast imaging of soft polymers combined with simultaneous material contrast based on surface viscoelastic properties. Hence, the spatial distribution of multi-component polymers can be determined. Micro-thermal analysis combines the visualisation power of AFM with the characterisation ability of thermal analysis.

5.4 Surface Hardness There is no single technique for measuring hardness which covers the range of hardness values available in plastics. Therefore, it is necessary to quote four different hardness scales. In decreasing order of hardness they are: RM123: Rockwell 123 (hard) RR112: Rockwell R112 (intermediate hardness)

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Miscellaneous Polymer Properties SD75: Shore D 75 (intermediate hardness) SA65: Shore A 65(soft) Various types of hardness meters are available from ATS FAAR including International Rubber Hardness Degree, Shore, Rockwell, and Fiat for testing against ASTM, ISO, UNI, DIN and FIAT speciications. The Martin Instrument Company is also a supplier of Shore hardness meters. Hardness measurements have recently been reported on methacrylate dental resins [31], polymeric coatings based on polyester resin, PU and acrylic acid [32], polyacrylamide [33] and aged PE [34]. Polymers range in hardness from relatively soft such as LDPE (Shore hardnesses of SD48 to SD58) to relatively hard polymers such as polyesters (Shore hardness of RM 125).

5.5 Haze, Glass and Surface Roughness Several workers have discussed these phenomena [35-38]. Sukhadia and co-workers [36, 37] characterised linear LDPE by measuring melt rheology and molecular weight. Film was characterised using AFM, small-angle light scattering, and haze measurements. There was a complex parabolic relationship between the haze, which was primarily caused by surface roughness, and the logarithm of the recoverable shear strain parameter (log RSSP). At low RSSP values, the haze increased as a consequence of increasing surface roughness due to the formation of optically anisotropic spherulite-like superstructures. With increasing RSSP the superstructures reduced and an oriented, row-nucleated stacked lamellar texture developed, which decreased surface roughness and total haze. At even higher log RSSP values, ine scale surface roughness caused by high melt elastic instabilities developed, which increased surface roughness and total haze. Spherulitic superstructures were formed at low shear strains and an oriented, rownucleated stacked lamellar texture developed with increasing shear strain. At higher recoverable shear strain values, a ine surface roughness developed due to high melt elastic instabilities. The bulk haze contribution was measured by applying a very thin layer of silicone oil to the ilm surface prior to measurement. The predominant contribution to the haze was from the surface, and was the result of surface roughness. The surface haze of metallocene-catalysed PE ilms was increased by the development of spheruliticlike surface features, which increased the surface roughness. However, Ziegler-Natta catalysed PE, exhibited relatively low total and surface haze values, which were attributed to the relatively smooth surface texture.

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Engineering Plastics Krishnaswamy and Stark [38] used a continuous method to count and size optical defects (gels/isheyes) of clear ilms of LDPE using high-speed cameras and image processing electronics. The results obtained clearly showed that the quantitative analysis of defects in clear ilms was very sensitive to factors such as line speed, ilm inspection width, instrument threshold settings and wrinkles. These factors should, therefore, be kept constant and/or reported along with the optical quality (defect count) results. This was essential for consistency in lab-to-lab and sample-to-sample analysis, while automatic inspection was a large step forward from visual inspections, it was evident that such gel counts were qualitative at best. They were by no means an absolute measure of the number of gels in the ilm. Extreme caution should, therefore, be exercised in interpreting such data, i.e., the gel count numbers should only be used as a qualitative indicator of the overall ‘cleanliness’ of a resin lot. Bafna and co-workers [39] also studied optical properties such as haze, gloss and transparency of blown PE ilm and investigated the structural factors affecting these optical properties. Two HDPE blown ilms were studied, one prepared using a ZieglerNatta single catalyst and a STAR α ilm synthesis with a single site catalyst. The STAR α ilm showed high clarity and gloss and the Ziegler-Natta ilm was turbid. The ilms were blown under similar conditions and both were transparent on extrusion, but the Ziegler-Natta ilm turned hazy at a well-deined frost line. Small-angle X-ray scattering, small-angle light scattering and optical microscopy were used to study the structure and orientation of the ilms. Both ilms had similar lamellar structures, the main difference was the degree of orientation. The Ziegler-Natta ilm had regularly arranged lamellae which were oriented normally along the with machine direction of the ilm. The orientation was linked to the formation of micrometer scale, rod-like structures, which gave a rough surface leading to scattering of light and haziness. The STAR α ilm showed lower orientation, less surface roughness and was clearer. Kuboky and co-workers [40] used transmission electron microscopy (TEM) to study ‘block’ and white crazes in high impact polystyrene (PS). They examined the mechanism of block craze formation and found that the rubber molecules were not necessarily diffused into the entire crazes. The length of the block crazes varied before they turned to white and in some cases only white crazes were generated from the rubber particles. TEM should thus be used with caution in examining stained rubber-toughened polymers to ensure that all crazes, including the white crazes, were considered for evaluation of the extent of the deformation behaviour [41]. Woods and Pocius [42] prepared commercial polyolein plastomer ilms, containing slip and antiblock, were blown with and without the addition of commercial polymer processing additives, at levels of 600, 1,200, or 2,000 ppm. Possible detrimental affects on the ilms were evaluated by determination of surface tension, gloss, haze, clarity, transmittance, hot tack, heat seal, coeficient of friction and block, and the surface

134

Miscellaneous Polymer Properties composition of the ilms was characterised using electron spectroscopy for chemical analysis and static secondary ion mass spectrometry. The addition of additives at typical dose levels had no detrimental effect on the plastomer ilm surface or their optical properties. Zhang and co-workers [43] tested poly-n-butylacrylate (PBA) ilms with a sapphire indenter with a spherical tip with uncrosslinked PBA ilm, the surface of which was sticky. The horizontal or scratching force decreased with decreasing normal load and had a residual value (about 6 mN) as the normal load approached zero. The relationship between the scratching force and the normal load could be determined by inite element calculations based on the Johnson-Kendall-Roberts theory under the assumption that the scratching force was proportional to the contact area, which is dependent on the normal load. With increasing driving speed, the scratching force showed a power relationship with the speed indicating a rate process. For crosslinked PBA ilm, which behaved as an elastomer, the horizontal force approached zero at zero normal load. Below a critical normal load, which depended on the thickness of the ilm, the crosslinked ilm recovered elastically after being scratched. Above the critical load, the ilm was damaged and, depending on its thickness, showed two distinct damage mechanisms.

5.6 Weathering Properties of Engineering Plastics Weathering tests can be carried out either as an accelerated test in the laboratory, for example using an Atlas xenon arc Weather-Ometer® according to ASTM D822/ D822M [44] or ASTM G155 [45] or it can be carried out using a natural outdoor weathering test. Accelerated test results have been reported on several polymers including HDPE [46], PA 6,6 [47], and a cyanate ester resin/carbon ibre composite [48]. For outdoor natural weathering, the site chosen would usually be a hot climate such as the Arizona desert (USA) or Miami (FL, USA) or Curaçao (a Caribbean Island off the North coast of Venezuela). Miami, greatly differs from Arizona and Curaçao in atmospheric conditions. Because of the elevation (6,000 m above sea level) and the clear daytime atmosphere (38% relative humidity as the annual average), the percentage of ultraviolet (UV) in the solar radiation is higher in Arizona and Curaçao than it is in the humid climate at sea level in Miami. Arizona has 4,000 sun hours compared to the UK with 1,000−1,400 sun hours. Thus, with natural unstabilised, unpigmented polymers the outdoor life in sunlight for PP is 135 h in Curaçao, 50 h in Arizona, compared to 590 h in the UK. Protecting PP with an intervening layer of glass, as for example, automobile windscreen facias exposed to sunlight, improves

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Engineering Plastics the outdoor life of PP from 135−380 h in Curaçao and from 50−880 h in Arizona, i.e., better than the performance of PP in the UK when not protected by glass. In contrast to ferrous metals, plastic materials do not suffer from the disadvantages of corrosion, but in common with most organic materials they are degraded by sunlight. The chemical basis of such photodegradation consists, in polyolefins, of chain scission accompanied by oxidation. This results in deterioration of the mechanical and electrical properties and of the surface appearance of polymer. Resistance to photodegradation varies and the following groups of polymers show decreasing light stability in the order LDPE>HDPE>PP>PS. It is, of course, well known that opaque pigments can have a valuable screening effect when incorporated into a plastic and can help to confine the photodegradation to the extreme surface layers, thus protecting the inner layers of the material. The most effective of such pigments is carbon black, although care has to be exercised in the choice of the grade of carbon black and the concentration used to ensure maximum protection while avoiding any side effects on other polymer characteristics. The addition of 2% by weight of a well dispersed carbon black of fine particle size should extend the outdoor life of most LDPE and HDPE to as much as 20 years in temperate climates, whilst even the addition of 0.2% should give 10 years life in temperate climates and three years in tropical climates. PP pigmented with 2% carbon black has shown such resistance to photodegradation that no obvious adverse effects could be detected after two years exposure under conditions found in Curaçao. The effect on the life of a PP in which contains various coloured pigments is judged by comparing polymer life for the unpigmented and the pigmented polymers both alone and in conjunction with a UV stabiliser. It is natural to expect that the polymer degradation resulting from sunlight exposure will be most acute at the surface of the plastic and this is borne out by all the experimental evidence. UV stabilisers, apart from reducing the rate of photodegradation, also restrict the depth to which photodegradation can occur (effectively 0. 05 cm for natural PP). These intense surface effects must be clearly borne in mind when considering the effect of outdoor weathering on all mechanical properties involving a flexural type of stress. For example, although PP shows powdering rather than gross surface crazing after sunlight exposure, minute surface cracks are visible under microscopic examination. Under certain circumstances these micro-cracks can act as points of stress concentrations similar to the sharp notch used in the Izod test. For example, where the unexposed surface is struck and the exposed surface is thereby placed in tension, surface micro-crazing can substantially reduce the impact strength of the component. Conversely, where the exposed micro-crazed surface is struck and placed in compression, the reduction in impact strength is considerably less. It is fortunate

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Miscellaneous Polymer Properties that the latter generally happens in practice. The rate of loss impact strength on exposure to sunlight has been found to be approximately independent of thickness for sections in excess of 0.3 cm thick up to 0.6 cm thick. However, while the impact strength of very thin sections is highly inluenced by surface degradation effects, this phenomenon is of relatively small practical importance for sections greater than 0.3 cm, provided it is the exposed surface that is struck. In any discussion of the application of standard test piece exposure results to the prediction of the exposure life of an actual component, consideration must, of course, be given to geometric and environmental factors. The most important factors to be taken into account in estimating the outdoor service life of an article are: •  Whether or not the article will be exposed continuously outdoors.  •  The position of the article relative to the horizon and the latitude of exposure.  •  Whether the article will be exposed in the open or in partial shade.  •  The thickness of the article in relation to impact strength requirements.  •  The importance of surface appearance.  As an example of the type of testing that can be carried out in weather tests, Severini and co-workers [49] investigated the suitability of an ethylene-carbon monoxide copolymer by carrying out tests over a wide range of weathering times. Photodegradation of the polymer and loss of mechanical properties is accompanied by the conversion of methyl groups to C-O-C groups.

5.7 Chemical Resistance The following polymers have a good resistance to chemicals: epoxy resins, LDPE, PC, PMMA, PPS, glass ibre reinforced ethylene chlorotriluoroethylene (with or without perluoroalkoxy glass ibre reinforcement), perluoroalkoxyethylene (with or without glass ibre reinforcing agents), PVF (20% carbon ibre reinforced), chlorotriluoroethylene, luorinated ethylene-propylene (with or without glass ibre reinforcing agents) and silicones.

5.8 Detergent Resistance In an assessment of the resistance of the material to industrial and domestic detergents at room temperature an excellent rating indicates excellent resistance to detergents. A very poor rating indicates poor resistance to detergents. 137

Engineering Plastics It is shown in Table 5.2 that polymer resistance to detergents can range from poor (HDPE) to excellent (e.g., crosslinked PE, polyoxymethylene, PEEK, diallyisophthalate, diallyl phthlate, PA 6,11 and PA 6,12, PEI and luorinated polymers). Thus, HDPE is not a serious contender for packaging detergent whereas PE provides a combination of detergent resistance and low cost.

5.9 Solvent Resistance Solvent and chemical resistant engineering polymers are of particular importance in applications such as storage containers, chemical plants and vehicles. Polymers with particularly good solvent resistance include PEEK, epoxy resins, polymethylpentene, PP, HDPE, LDPE, PI, PA 4,6, PA 11, PAI, polyether sulfone, PPS and PTFE.

Table 5.2 Detergent resistance, hydrolytic stability and water absorption of polymers Polymer

Detergent resistance ABS terpolymer Good Acrylate-styrene-acrylonitrile terpolymer Very good Alky resins (mineral illed) Very good Chlorinated PVC Excellent Diallyl isophthalate Excellent Diallyl phthalate Excellent Epoxies Very good Ethylene chlorotriluoroethylene Excellent Ethylene-propylene polymer Good EVA copolymer Good Fluorinated ethylene-propylene copolymer Excellent HDPE Poor LDPE Poor PA 11 Very good PA 12 Very good PA 6 Very Good PA 6,10 Excellent PA 6,11 Excellent PA 6,12 Excellent PA 6,6 Very good PAI Very good

138

Hydrolytic stability Very good Very good Poor Very good Poor Very good Good Excellent Excellent Very Good Excellent Excellent Excellent Good Very good Good Good Good Good Poor Poor

Water absorption Good (0.4%) Poor (0.5%) Good (0.20%) Very good (0.01%) Good (0.25%) Poor (0.2%) Good (0.2%) Excellent (0.01%) Excellent (0.01%) Very good (0.05%) Excellent (0.01%) Excellent (0.02%) Excellent (0.01%) Poor (0.3%) Good (0.25%) Very Poor Poor Poor (0.45%) Good (0.25%) Poor (1.2%) Good (0.28%)

Miscellaneous Polymer Properties PC PEI Perluoroalkoxyethylene PES PET Phenol-formaldehyde PI Plasticised PVC PMMA Polyacrylamide Polybutylene Polyether ketone Polymethyl pentene Polyoxymethylene PP PPO PPS PS PSU PTFE PVDF Polyvinyl luoride Silica Styrene-acrylonitrile copolymer Styrene-butadiene copolymer Styrene-butylene-styrene terpolymer Styrene-malic anhydride copolymer UHMWPE Unplasticised PVC Urea-formaldehyde XPE PVC: Polyvinyl chloride Source: Author’s own iles

Good Excellent Excellent Excellent Very good Very good Very good Excellent Very good Very good Very good Excellent Very good Excellent Very good Very good Excellent Very good Excellent Excellent Excellent Excellent Very good Good Very good Very good Excellent Excellent Excellent Very good Excellent

Poor Good Excellent Very good Poor Poor Poor Very good Poor Very good Excellent Very good Very good Very good Very good Good Very good Excellent Very good Excellent Excellent Excellent Very good Very good Very good Good Poor Excellent Very good Good Excellent

Poor (0.11%) Good (0.26%) Very good (0.03%) Very good (0.1%) Very good (0.1%) Very poor (0.08%) Good (0.3%) Poor (0.3%) Poor (0.3%) Good Excellent (0.01%) Very good (0.15%) Excellent (0.01%) Good (0.22%) Very good (0.04%) Poor (0.12%) Very good (0.03%) Very good (0.5%) Very good (0.1%) Excellent (0.01%) Very good (0.04%) Very good (0.05%) Very good (0.1%) Good (0.25%) Very good (0.08%) Poor (0.03%) Very good (0.1%) Excellent (0.01%) Very good (0.1%) Poor (0.6%) Excellent (0.01%)

The Automobile Association in the UK [50] has reported a study on the effect of unleaded petrol on the use of plastics in cars, particularly car engines. It was found that the alcohols, solvents and high aromatic fractions used as replacements for lead additives in petrol will have a detrimental effect upon plastic components, which will come into contact with the fuel, such as fuel lines and PU loats.

139

Engineering Plastics Researchers at ICI Engineering Plastics [51] have shown that PA 6,6 diluted with up to 15% methanol or ethanol or certain mixtures of methanol and acetone, all of which are being considered as newer types of fuels, can be used satisfactorily in contact with petrol. This is of considerable importance when considering storage tanks for such fuels. Lagaron and Powell [52] made measurements of the permeation rates of methanol, toluene and a 50:50 toluene:isooctane fuel (fuel C) and fuel C with addition of 10% ethanol or 15% methanol through ethylene-vinyl alcohol (EVOH) ilms. Large scale methanol and water-induced plasticisation was suggested by the large solvent uptakes and conirmed by the observation of a considerable decrease in the glass transition temperature. The permeability of fuel C increased signiicantly when methanol was present, while the high barrier properties of EVOH by hydrocarbons was maintained for fuel C containing ethanol.

5.10 Hydrolytic Stability and Water Absorption Water absorption represents the tendency of the materials to absorb moisture. Absorption of moisture usually results in changes in electrical and mechanical properties and also in physical dimensions. The ratings are based on the weight gain of a sample after immersion in water at room temperature for 24 h. It is shown in Table 5.2 that water absorptions range from 0.5−1.2% (poor), for example, PA 6,6,10 and 6,11, to below 0.02% (excellent), for example, HDPE, PTFE and other fluorinated polymers. Very few polymers exhibit a combination of low water absorption and excellent hydrolytic stability. Those that do include PTFE, ethylene chlorotrifluoroethylene copolymers and fluorinated ethylene-propylene copolymer. ASTM D570 [53] and DIN 7708 [54] test methods are for the determination of the water absorption of polymers. Adriaensens and co-workers [55] studied the water uptake of PA 4,6 based copolymers by magnetic resonance imaging relaxometry. These tests showed that increasing the copolymer alkyl chain length reduces the rate of water absorption and water molecular mobility because of a combination of reduced crystallinity and improved coupling of the amide groups in the amorphous phase. Annealed samples showed reduced water absorption and this indicated the importance of the amorphous phase morphology on water absorption properties. Water uptake mechanisms are discussed. Water uptake studies have also been carried out on PA11 [56] and PI [57] (see also Table 5.2). For both these the polymers water absorption was about 0.3%.

140

Miscellaneous Polymer Properties Kint and co-workers [58] studied the hydrolytic degradation of a series of PET copolymers containing nitrated units at 80 °C. These polymers degraded more rapidly than semi-crystalline and amorphous PET and the degradation rate increased with the concentration of nitrated units. Differential scanning calorimetry (DSC) measurements showed that the melting point of the semi-crystalline samples increased slightly with hydrolytic degradation, while the degree of crystallinity remained essentially unchanged. Nuclear magnetic resonance spectroscopy showed that hydrolysis occurred preferentially by cleavage of the ester groups of the nitrated units and that most of the degradation products remained in the degraded polymer samples.

5.11 Gas Barrier Properties of Plastics The use of polymer-based structures as packaging materials for foodstuffs has been increasing over the 15−20 years. The main commercial appeal of these materials lies in their ability to offer a broad variety of tailor-made properties and yet be inexpensive, and easily processed and conformed into a myriad of shapes and sizes. Given the diversity of food products and the various packaging requirements of these, a large number of packaging technologies have also been put into place for example, multilayer structures, modified and equilibrium modified atmosphere packaging, active packaging, and so on [59]. Nevertheless, one of the limiting properties of polymeric materials in the food packaging field is their inherent permeability to low molecular weight substances, including permeable gases, water and organic vapours. This has boosted the interest for developing new resins with higher gas barrier properties and in carrying out research aimed at understanding the structure/barrier properties relationship. The most efficient and widely used higher barrier polymeric materials are the EVOH copolymers, and to a lesser extent, aliphatic polyketones and thermoformable EVOH-based blends [60]. As stated previously, barrier properties in polymers are by necessity associated with their inherent ability to permit the exchange, to a greater or lesser extent, of low molecular weight substances by mass transport processes such as permeation. The permeation of low molecular weight chemical species usually takes place in the polymer amorphous phase and is generally envisaged as a combination of two processes, sorption and diffusion. A permeate gas is first sorbed into the upstream face of the polymer film, and then, undergoes a molecular diffusion to the downstream face of the film where it desorbs into the external phase again. A sorption-diffusion mechanism is thus applied which can be formally expressed in terms of permeability (P), this being the product of solubility (S) and diffusion (D) coefficients, as defined by Henry’s and Fick’s laws, respectively.

141

Engineering Plastics For food packages, polymeric materials should exhibit an adequate carbon dioxide:oxygen ratio (generally lower than 7). The process of permeation involves dissolution of the gas in one side of the membrane, diffusion of the gas through it and release of the gas from the other side of the membrane. A conventional method for determining permeability and diffusion coeficients in polymers involves the measurement of membrane weight gain versus time until the inal mass equilibrium mass is reached. Active packaging has been used for years in Japan, and to some extent, in Europe and the US. Europe does not have many commercial products on the market because of legislative restrictions. However, in 2003, the European Commission accepted amendments to the framework directive for food contact materials that will allow the use of active and intelligent packaging. In the US, regulatory issues limit anti-microbial use, but other areas in which active packaging can add value are growing. Active packaging has good growth potential in single-serve and fresh cut produce packaging where higher value, higher margin products support the use of more sophisticated packaging systems that extend shelf life. Auras and co-workers [61] studied the variations in the oxygen diffusion solubility, permeability coefficients and water sorption of polylactide films at different temperatures (5, 23, and 40 °C) and water activities (Aw = 0-0. 9). The results were compared with the oxygen diffusion, solubility and permeability coeficients obtained for PET ilms under the same experimental conditions. Diffusion coeficients were determined using the half-sorption time method. Oxygen underwent Fickian diffusion in the polylactide ilms. The permeability coeficients were obtained from steady-state permeability experiments. With polylactide ilms very low amounts of water were absorbed, and no signiicant variation of the absorbed water with temperature were found. The oxygen permeability coeficients obtained for polylactide ilms (2−12 × 10-18 kg m/m2-s Pa) were higher than those obtained for PET films (1−6 × 10-18 kg m/m2-s Pa) at different temperatures and Aw. Furthermore, the permeability coefficients for polylactide and PET films did not change significantly with changes in the Aw at temperatures lower than 23 °C. A typical plot of oxygen permeation as a function of time is shown in Figure 5.3 for PET films at 5, 23 and 40 °C at Aw = 0.9. Techniques used to determine the diffusion of oxygen and carbon dioxide through PE film were applied to the determination of diffusion coefficients for LDPE. The methodology involved the monitoring of diffused gas by a photoacoustic analyser. Diffusion coefficients measured for carbon dioxide and oxygen were 2.77 × 10–8 cm2/s and 1.68 × 10–7 cm2/s, respectively. To support the gas diffusion results, thermal properties were studied using photoacoustic spectroscopy and

142

Miscellaneous Polymer Properties crystallinity was determined using X-ray diffraction. Values obtained for thermal diffusivity and speciic heat capacity of PET were 1.65 × 10–3cm2 and 2.33 J/cm3/K, respectively, which were in good agreement with the values available in the literature for pure LDPE and this assured the reliability of the diffusion coeficient values.

Flow fraction, φ

1.00 0.80 0.60 5 °C, exp. 5 °C, calc. 23 °C, exp. 23 °C, calc. 40 °C, exp. 40 °C, calc.

0.40 0.20 0.00 0

1000

2000 Time, s

3000

4000

Figure 5.3 Permeation low fraction versus time for oxygen permeation experiments for PET ilms at 5, 23 and 40 °C (Aw = 0. 9). Reproduced with permission from R. Auras, B. Arte and S. Selke, Journal of Applied Polymer Science, 2004, 92, 3, 1790. ©2004, Wiley [61]

Permeation studies of carbon dioxide and oxygen were performed using a sample holder which, has its sides sealed off one from another. The permeate gas being studied was introduced on one side and kept at a constant pressure of 0.10 MPa. On the other side the concentration of the gas was measured using photoacoustic gas analyser. The gas concentration (C), in these conditions, is given by [62]:

(5.1)

Where: C0: Gas concentration at saturation; 143

Engineering Plastics τi: 1s2/2D = gas diffusion time; D: Gas diffusion coeficient; and 1: Sample thickness (40 µm in this case). When the gas concentration is plotted against time, equilibrium is reached at a concentration of 2% for carbon dioxide and at 22% for oxygen. The values obtained for diffusion coeficients of LDPE to oxygen and carbon dioxide were 1.68 × 10–7 cm2/s and 2.77 × 10–8 cm2/s, respectively. These values are in reasonable agreement with those in the literature for LDPE (6.9 × 10–8 cm2/s for carbon dioxide and 4.6 × 10–7 cm2/s for oxygen). Diffusion coeficients have been measured for carbon dioxide, oxygen and water vapour though polyoleins [62-65], EVOH [66-69] and PET ilms [70].

5.12 Prediction of Polymer Service Lifetimes A practical and accurate method for predicting the useful service life of polymers has long been sought. The need has become increasingly critical with the development of new materials and demanding applications, particularly those in which engineering plastics and composites are substituted for metals. The proliferation of materials gives scientists and engineers new design freedom. It also represents a considerable challenge. Before the best material for an application can be selected, the required performance properties (such as rigidity, strength, impact resistance, and creep) and the environment in which the product will operate must be deined. Then, the desired life expectancy for the product must be determined. Only then can the material selection process begin. Traditional evaluation procedures are generally laborious, time consuming, and expensive because they require fabrication of prototype parts and testing under actual end-use or simulated service conditions. These processes are more empirical than analytical, making the results of questionable value. The processes are generally impractical because they require months or years to produce results. Sichina [71] has discussed the applications of the dynamic mechanical analysis (DMA) to the prediction of polymer lifetimes and long-term performances, e.g., creep in gaskets, stress relaxation in snap-it parts, modulus decay in composite structural beams, creep in bolted plates and heat deformation frequencies in structural parts. The ability of this system to generate master curves makes the prediction of product

144

Miscellaneous Polymer Properties performance fast and easy and facilities the correlation of DMA data with evaluations performed by traditional time and labour intensive methods. Haschki [72] has conducted a study of the use of DMA in helping designers of plastic parts build products with increased durability. The technique measures the mechanical response of materials subjected to periodic stress at their operating temperature. Tests can be conigured for pure tension or compression, single or dual cantilever, and three-point bend modes. Details are given of the test procedure, capabilities of the test method and typical testing applications. Dedecker and co-workers [73] discuss the extensive efforts that have been made to deine a method, which can be used to declare aged thermal conductivity, which is described in Annex C of the EN13165 [74] standard. Quality data on long-term thermal conductivity (lambda) values are quite rare, especially for foams made with blowing agents such as pentane, which have only been used commercially for about 10 years. As a result, the design of this standard was based mainly on calculations and modelling. A lambda ageing predictive model (AgeSim), developed by Huntsman Polyurethanes, was used extensively to design the standard. The intention of EN13165, Annex C is to provide an estimate of the average lambda value during 25 years of use under operational conditions. The board producer can choose between two basic routes to get to this value. The irst route is called the ixed increment method. This is based on initial lambda measurement followed by the addition of a ixed increment, which depends on blowing agent, board thickness and diffusion tightness of the facing. A test showing that the product has a normal ageing behaviour (called the normality test) needs to be passed before using this ixed increment method. A second route is called the accelerated ageing method. It is based on a lambda measurement after storing the board for 25 weeks at 70 °C, followed by the addition of a safety increment. This safety increment can be reduced, depending on the outcome of an acceleration test. Special attention has been given to new experimental test conditions, such as the 25 weeks at 70 °C ageing test and the acceleration test, which were not used previously. This paper shows what range of declared lambda values are to be expected using this new method. These declared lambda values are then compared to 25-year predictions using the Huntsman Polyurethanes lambda ageing predictive model. Erzin [75] reviewed the inluence of material, (compression, molecular weight and intermolecular order), design and processing on the failure of plastic products and discusses failure analysis and testing. This involved measurements of rheological

145

Engineering Plastics properties and the application of thermogravimetric analysis, DSC, thermal desorption/gas chromatography/mass spectrometry, X-ray photoelectron spectroscopy, acoustic emission and ultrasonic spectroscopy to these problems. The service lifetime of a polymer at various temperatures can be estimated from kinetic data. Ozawa [76] observed that the activation energy of a thermal event could be determined from a series of thermogravimetric runs performed at different heating rates. As the heating rate increased, the thermogravimetric change occurred at higher temperatures. A linear correlation was obtained by plotting the logarithm of the heating rate or scan speed against the reciprocal of the absolute temperature at the same conversion or weight loss percentage. The slope was directly proportional to the activation energy and known constants. To minimise errors in calculations, approximations were used to calculate the exponential integral i.e., the relationship between the rate constant and half-life [77-79]. It was assumed that the initial thermogravimetric decomposition curve (2–20% conversion) obeyed irst order kinetics. Rate constants and pre-exponential factors could then be calculated and used to examine relationships between temperature, time and conversion levels. The thermogravimetric decomposition kinetics could be used to calculate: 1. The lifetime of the sample at selected temperatures. 2. The temperature, which will give a selected lifetime. 3. The lifetime at all temperatures at known percentage conversion. Glass ibre/resin reinforced bars used for the reinforcement of concrete are subject to alkali corrosion by the alkali present in concrete and this is a major cause of deterioration of the tensile properties of reinforced concrete. Chen and co-workers [80], Bank and co-workers [81] and Gonenc [82] developed a procedure based on the Arrhenius relationship to predict the long-term behaviour of glass-reinforced resin bars in concrete structures, based on short-term data from aging tests. Glass ibre-reinforced plastics (GFRP) reinforcing bars were exposed to simulated concrete pore solutions at 20, 40, and 60 °C. The tensile strength of the bars determined before and after exposure were considered to be a measure of the durability performance of the specimens (Figure 5.4 and Figure 5.5). Based on the short-term data a procedure was developed and veriied to predict the long-term durability performance of GFRP bars. A modiied Arrhenius analysis was included in the procedure to evaluate the validity of the accelerated ageing tests before the prediction was made. The accelerated test and prediction procedure used in this study can be a reliable method to evaluate the durability performance of ibre-reinforced plastics composites exposed to solutions or in contact with concrete.

146

In (time in days to reach a given tensile strength of GFRP1 bars)

Miscellaneous Polymer Properties 8 80% Retention 70% Retention

7

60% Retention 6

50% Retention

5 4 3 2.9

3

3.1

3.2

3.3

3.4

3.5

1/T × 1000 (1/K)

In (time in days to reach a given tensile strength of GFRP2 bars)

Figure 5.4 Tensile strength retention of GFRP bars exposed to Solution 1 (NaOH: 2.4 g/l, KOH: 10.6 g/l, Ca(OH)2: 29 g/l) at 20, 40 and 60 °C. Reproduced with permission from Y. Chen, J.F. Davalos and I. Ray, Journal of Composites for Construction, 2006, 10, 4, 279. ©2006, ASCE [80]

8 80% Retention 70% Retention 60% Retention 50% Retention

7 6 5 4 3 2.9

3

3.1

3.2

3.3

3.4

3.5

1/T × 1000 (1/K)

Figure 5.5 Tensile strength retention of GFRP bars exposed to Solution 2 (NaOH: 0.69 g/l, KOH: 19.5 g/l, Ca(OH)2: 0.037 g/l) at 20, 40 and 60 °C. Reproduced with permission from Y. Chen, J.F. Davalos and I. Ray, Journal of Composites for Construction, 2006, 10, 4, 279. ©2006, ASCE [80]

147

Engineering Plastics It is seen in Figure 5.5, that the tensile strength of test bars decreased with increase in exposure time for the bars at all temperatures and as expected degradation was more severe for specimens in solutions at higher temperatures. Because the basic steps of this procedure would apply to many polymer lifetime studies they are discussed next in some detail. In the Arrhenius relationship, the degradation rate is expressed as [83]:

k = A exp ` - E a j RT

(5.2)

Where: k: Degradation rate (1/time); A: Constant of the material and degradation process; Ea: Activation energy; R: Universal gas constant; and T: Temperature (˚K). The primary assumption of this model is that the single dominant degradation mechanism of the material will not change with time and temperature during the exposure, but the rate of degradation will be accelerated with the increase in temperature. Equation 5.2 can be transformed into:

1 = 1 exp E a ` j k A RT

(5.3)

From Equation 5.3, the degradation rate k can be expressed as the inverse of time needed for a material property to reach a given value. From Equation 5.4 one can further observe that the logarithm of time needed for a material property to reach a given value is a linear function of 1/T with the slope of Ea/R:

ln ` 1 j = E a 1 - ln ^ Ah k R T

148

(5.4)

Miscellaneous Polymer Properties For the irst step, the relationship between the tensile strength retention (the percentage of residual strength over original tensile strength) of glass ibre reinforced concrete bars and the exposure time for the accelerated test was deined as:

Y = 100 exp c - 1 m xi

(5.5)

Where: Y: Tensile strength retention value (%); and τ: 1/k, as expressed in Equation 5.4. The form of this equation was modiied from a study by Phani and Bose [84] by assuming that the GFRP bars degraded completely at ininite exposure time. This data was used in Equation 5.5 to obtain the coeficient τ by regression analysis. Corresponding τ values and correlation coeficients (r) are summarised in Table 5.3, with all the regression lines having a correlation coeficient above 0.93. Thus, the time to reach a given tensile strength retention at different temperatures can be calculated approximately through Equation 5.4.

Table 5.3 Coefficient of regression equations for GFRP tensile strength retention Temperature (°C)

GFRP bars in solution 1 GFRP bars in solution 2 r r τ τ 60 143 0.93 222 0.99 40 200 0.98 714 0.96 20 256 0.96 1,667 0.94 Solution 1: NaOH 2.4 g/l, KOH 19.6 g/l, Ca(OH)2g/l Solution 2: NaOH 0.6 g/l, KOH12.4 g/l, Ca(OH)2 0.037 g/l Reproduced with permission from Y. Chen, J.F. Davalos and I. Ray, Journal of Composites for Construction, 2006, 10, 4, 279. ©2008, ASCE [80]

149

Engineering Plastics In the second step, the Arrhenius relationships were obtained by plotting the natural log of time to reach 50, 60, 70 and 80% tensile strength of GFRP bars versus 1/T (the inverse of exposure temperature). Straight lines were itted to the data with the assumption that the degradation rate was a function of temperature as expressed in Equation 5.3. Equation 5.2 was also itted to the data of Table 5.3 to obtain Ea/R. From the analysis, the regression coeficients (Ea/R and correlation coeficients (r) are listed in Table 5.4). The correlation coeficients for all the regression lines were close to one, and straight lines in Arrhenius plots for different strength retentions were nearly parallel to each other (the slopes of straight lines are Ea/R). This implies that the Arrhenius relationship can be used to describe the degradation rate of GFRP bars, as the degradation mechanism may not change with temperature and time during exposure in the range tested. Furthermore, Equation 5.4 can be used to deine the time and temperature dependence of tensile strength for GFRP bars exposed to alkaline solutions

Table 5.4 Coefficient of regression equations for Arrhenius plots Tensile strength retention (%)

GFRP bars in solution 1 Ea/R r 1,420 0.99 1,423 0.99 1,420 0.99 1,420 0.99 1,415 0.99

GFRP bars in solution 2 Ea/R r 4,891 0.99 4,892 0.99 4,891 0.99 4,892 0.99 4,899 0.99

50 60 70 80 Equation 5.3 Ea: activation energy Solution 1: NaOH 2.4 g/l, KOH 19.6 g/l, Ca(OH)2 2 g/l Solution 2: NaOH 0.6 g/l, KOH 1.4 g/l, Ca(OH)2 0.037 g/l Reproduced with permission from Y. Chen, J.F. Davalos and I. Ray, Journal of Composites for Construction, 2006, 10, 4, 279. ©2008, ASCE [80]

For the third step, the acceleration factor (AF) for the same solution at two different temperatures can be obtained from previous Arrhenius plots. The AF can be expressed as:

- Ea A exp c m RT1 E t clk k 0 0 1 = = AF = = = exp ; a c 1 - 1 mE R T0 T1 E t1 clk 1 k0 a A exp c m RT0

150

(5.6)

Miscellaneous Polymer Properties Where: AF: Acceleration factor; t1 and t0: Time required for acceleration factor to reach a given value at temperatures of T1 and T0, respectively; c: Constant; and k1 and k0: Degradation rates at temperatures of T1 and T0, respectively, as expressed in Equation 5.2. Compared to the procedures proposed by other researchers [85], the procedure in this study can be used to obtain short-term data for GFRP bars successfully and eficiently. The proposed procedure can easily be carried out by deining simple plots and performing regression analysis. The results indicated that increasing the number of exposure temperatures and using longer exposure durations in accelerated tests can lead to more precise predictions. From the master curves shown in Figures 5.4 and 5.5 the tensile strength retention of GFRP bars drops to 50% after only a half-year exposure to Solution 1 consisting of NaOH (2.4 g/l), KOH (10.6 g/l) and Ca(OH)2 (2 g/l) at 20 °C, and for GFRP bars exposed to Solution 2 consisting of NaOH (0.69 g/l), KOH (19.5 g/l), Ca(OH)2 (0.037 g/l) at 20 °C, the tensile strength retention is 50% after about three years. But in a recent study by Mufti and co-workers [86], much less degradation was found for GFRP bars in concrete structures used in the ield. In the work of Chen and coworkers [79] GFRP reinforcing bars were directly exposed to simulated pore solutions. The reported short-term results and the predicted tensile strength retention should be considered conservative. Note also that the master curves in this work are only applicable to the GFRP bars tested to the speciic simulated pore solutions that they were exposed to in this study. To investigate the durability of GFRP bars in concrete, specimens embedded in concrete should be tested. To predict long-term behaviours of GFRP bars based on the shortterm data, the correlation between the degradation of GFRP bars in accelerated tests and real applications needs to be investigated. Long-term data, including those in real applications, should be collected to validate accelerated tests and prediction models. Furthermore, the coupling effects of sustained load and environmental exposures should also be included in future studies to simulate real-life conditions. Schröder and co-workers [87] have described a method for evaluating the expected lifetime of polyoleins to long-term atmospheric oxidation. Over expected lifetimes of 25−100 years this method is a departure from conventional methods of determining

151

Engineering Plastics the oxidation resistance of polymers which involves long-term testing at atmospheric pressure with forced air circulation at temperatures signiicantly higher than 80 °C. Schroder and co-workers [87] instead developed a method of assessing oxidative stability duration based on autoclave immersion at 60 and 80 °C and 1.2 and 5 MP oxygen concentration. Results of such accelerated tests were evaluated by means of a modiied Arrhenius equation. With autoclaving, results can usually be obtained in a period of time not exceeding 12 months as opposed to the many years of testing needed by conventional testing at 0.1 MPa. The basis for the calculation of polymer lifetime is based on exposure duration for 50% loss of residual maximum tensile load.

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Miscellaneous Polymer Properties 47. P.N. Thanki and R.P. Singh, Polymer, 1998, 39, 25, 6363. 48. K. Chung and J.C. Seferis, Polymer Degradation and Stability, 2001, 71, 3, 425. 49. F. Severini, R. Gallo, L. Di Landro, M. Pegoraro, L. Brambilla, M. Tommasini, C. Castiglioni and G. Zerbi, Polymer, 2001, 42, 8, 3609. 50. Chemistry and Industry, 1985, 1, 5. 51. The Effect of Petrol Additives on Maranyl Nylons, ICI Engineering Plastics, Wilton, UK, 1987. 52. J. M. Lagaron and A. K. Powell, Revista de Plasticos Modernos, 2001, 81, 536, 244. 53. ASTM D570, Test Method for Water Absorption of Plastics, 2010. 54.

DIN 7708-1, Plastics – Moulding Materials – Deinition of Terms, 1980.

55. P. Adriaensens, A. Pollaris, R. Rulkens, V.M. Litvinov and J. Gelan, Polymer, 2004, 45, 8, 2465. 56. A. Meyer, N. Jones, Y. Lin and D. Kranbuehl, Macromolecules, 2002, 35, 7, 2784. 57. I.K. Spiliopoulos and J.A. Mikroyannidis, Macromolecules, 1998, 31, 2, 515. 58. D.P.R. Kint, A.M. de Ilarduya and S. Muñoz-Guerra, Polymer Degradation and Stability, 2003, 79, 2, 353. 59. J.M. Lagaron, R. Catalá and R. Gavara, Materials Science and Technology, 2004, 20, 1, 1. 60. R. Gavara, R. Catala, J.M. Gimenez, J.M. Lagaron and S. Sanz in Proceedings of the 13th IAPRI Conference on Packaging - WorldPak 2002, East Lansing, MI, USA, 2002, Volume 1, p.400. 61. R. Auras, B. Harte and S. Selke, Journal of Applied Polymer Science, 2004, 92, 3, 1790. 62. L.H. Poley, A.P.L. Siqueira, M.G. de Silva and H. Vargas, Polimeros: Ciencia e Tecnologia, 2004, 14, 1, 8.

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Engineering Plastics 63. J.J. Wooster and B.A. Cobler in Proceedings of the 1994 TAPPI Polymers Laminations and Coatings Conference, Nashville, TN, USA, 1994, Book 2, p.153. 64. E. Epacher, J. Tolvélty, C. Kröhnke and B. Pukánszky, Polymer, 2000, 41, 23, 8401. 65. J.W. Qian, J.W. Cho and T. Lan in Proceedings of the SPE Polyoleins 2001 Conference, Houston, TX, USA, 2001, p.553. 66. J.C. Grunlan, A. Grigorian, C.B. Hamilton and A.R. Mehrabi, Journal of Applied Polymer Science, 2004, 93, 3, 1102. 67. M.L. Cerrada, Revista de Plasticos Modernos, 2001, 81, 536, 236. 68. J-T. Yeh S-S. Huang, W-H. Yao, I-J. Wang and C-C. Chen, Journal of Applied Polymer Science, 2004, 92, 4, 2528. 69. W. Michaeli, S. Göbel and R. Dhalmann, Journal of Polymer Engineering, 2004, 24, 1-3, 107. 70. R.M. Patel, P. Saavedra, J. de Groot, C. Hinton and R. Guerra in Proceedings of the TAPPI Polymers, Laminations and Coatings Conference, Toronto, Ontario, Canada, 1997, Book 1, p.239. 71. W.J. Sichina, International Laboratory, 1988, 181, 4, 36. 72. P.C. Haschke, Machine Design, 2001, 73, 16, 61. 73. K. Dedecker, M. Baes and S.N. Singh in Proceedings of the Crain Communications UTECH Europe 2003 Conference, The Hague, The Netherlands, 2003, Paper No.36. 74. EN 13165 Annex C, Thermal Insulation Products for Buildings - Factory Made Rigid Polyurethane Foam (PU) Products Speciication, 2013. 75. M. Ezrin in Proceedings of the 60th SPE ANTEC 2002 Conference, San Francisco, CA, USA, SPE, Brookield, CT, USA, Paper No.202. 76. T. Ozawa, Bulletin of the Chemical Society of Japan, 1965, 38, 11, 1881. 77. J.H. Flynn and L.A. Wall, Polymer Letters, 1966, 4, 5, 323. 78. C.D. Doyle, Journal of Applied Polymer Science, 1961, 5, 15, 285.

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Miscellaneous Polymer Properties 79. J. Zascó and J. Zascó, Jr., Journal of Thermal Analysis and Calorimetry, 1980, 19, 2, 333. 80. Y. Chen, J.F. Davalos and I. Ray, Journal of Composites for Construction, 2006, 10, 4, 279. 81. L.C. Bank, T.R. Gentry, B.P. Thompson and J.S. Russell, Construction and Building Materials, 2003, 17, 6-7, 405. 82. O. Gonenc in Durability and Service Life Prediction of Concrete Reinforcing Materials, University of Wisconsin, Madison, WI, USA, 2001. [MSc Thesis] 83. W.B. Nelson, Accelerated Testing – Statistical Models, Test Plans and Data Analysis, Wiley, New York, NY, USA, 1990. 84. K.K. Phani and N.R. Bose, Composites Science and Technology, 1987, 29, 2, 79. 85. A. Caceres, R.M. Jamond, T.A. Hoffard and L.J. Malvar in Accelerated Testing of Fibre Reinforced Polymer Matrix Composites – Test Plan, SP2091-SHR, Naval Facilities, Engineering Service Center, Port Hueneme, CA, USA, 2000. 86. A. Mufti, M. Onofrei, B. Benmokran, N. Banthia, M. Bouliza, B. Bakht, G. Tadros and P. Brett in Proceedings of the 7th International Symposium on Fiber-Reinforced Polymer (FRP) Reinforcement for Reinforced Concrete, Eds., C.K. Shield, J.P. Busel, S.L. Walkup and D.G. Gremel, American Concrete Institute, Farmington Hills, MI, USA, 2005, Paper No.77. 87. H.F. Schröder, M. Munz and M. Böhning in Proceedings of the 13th International Plastics Additives and Compounding Conference – Addcon World 2007, Frankfurt Germany, Paper No.7.

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Plastics in Automotive Engineering

6.1 Applications A wide range of plastics are now being used in interior, exterior and under the bonnet applications in the manufacture of automobiles. Some of the major applications are shown in Table 6.1.

Table 6.1 Automobile applications of plastics Plastic

Parts/components

PP

Under bonnet applications

PP, 20% talc illed

Under bonnet applications

PP, 20% glass ibre illed

Under bonnet applications

Ethylene-propylene copolymer

Car bumper applications

Ethylene-propylene elastomer

Car fascias

PPO

Automotive grills, fascia automotive panels

PPO, 10% glass ibre reinforced

Automotive instrument panels

PEEK, 20% glass ibre reinforced

Automotive applications

PEEK

Automotive engine parts

PMMA

Automotive components

PBT

Under-body parts

PBT, 10−20% glass ibre reinforced

Distributor caps

PET, 36% glass ibre reinforced

Exterior body parts, casings and housings of wiper arms

PET, 45−55% glass ibre reinforced

Automotive bumpers

PET (unreinforced)

Automotive mouldings

PET, 45% mineral and glass ibre reinforced (ire retardant)

Automotive ignition

PA 6

Fuel tanks, automotive door closures

PA 6, 30% glass ibre reinforced

Automotive parts

PA 6,6

Automotive applications

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PA 6,1, 40% mineral reinforced

Under bonnet mechanical parts

PA 6,6 (high impact)

Automotive parts

PA 6,6 carbon ibre reinforced

Connecting rods

PA 11

Hoses for automotive use

PA 11, 30% glass ibre reinforced

Fan blades

PA 12

Injection moulded automotive parts, fuel lines and air brakes

PA – PPO alloy

Automotive applications

Polyimide, 40% glass ibre reinforced Gear boxes PEI

Under bonnet applications

PEI, 10−30% glass ibre reinforced

Cooling fans, gears, under body components and fuel systems

Polyamide-imide

Parts for internal combustion engines: valves, gears and bearings

Chlorotriluoro ethylene

Chemical resistant O-rings

Chlorinated ethylene-propylene

Non-stick valves

PPS, glass ibre and bead reinforced

Headlamps, under bonnet applications and parts exposed to oil, petrol and hydraulic luid

PPS, 40% glass ibre reinforced

Headlamps, petrol, oil, and hydraulic luid resistant parts, exhaust emission and control valves

PPS, 20% PTFE lubricated

Anti-friction gears

PES

Under bonnet applications, gear box, air ducting and car heating fans

PSU

Under bonnet applications

PSU, 10% glass ibre reinforced

Under bonnet applications, electronics and ignition components

PSU, 30% carbon ibre reinforced

Under bonnet applications

PA: Polyamide PBT: Polybutylene terephthalate PEEK: Polyether ether ketone PEI: Polyether-imide PES: Polyether sulfone PET: Polyethylene terephthalate PMMA: Polymethyl methacrylate PP: Propylene PPO: Polyphenylene oxide PPS: Polyphenylene sulide PSU: Polysulfone Source: Authors’ own iles

Some applications of plastics in the automotive industry are reviewed in the next sections.

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6.1.1 Polypropylene and Polyethylene Polypropylene is used for large automotive exterior applications requiring durability, ductile impact properties at low temperature, excellent paintability and easy processability. Applications include bumpers and other large exterior parts. Botkin and co-workers [1] state that improvements in the performance of mechanical properties of the PP used in automotive engineering applications can be achieved through the use of nucleating agents. These additives function by promoting the crystallisation of PP during moulding, providing a wide range of beneits including improved moulding productivity, increased modulus without sacriicing impact strength, enhanced thermal properties and improved clarity for special visual effects. An overview is presented of the various types of nucleating agents and the effects they provide are compared. Glass ibre reinforcement of PP has been discussed by several workers [1-3]. PP formulations with exceptional properties have been developed [2]. This is because of the good overall properties of magnetite such as its thermal and electrical conductivity, its ferrimagnetism and its high density and hardness that have been developed. Apart from these speciic properties, it is particularly important in many applications, for example, in the automotive industry, for a illed plastic to have very good mechanical characteristics and to comply with the recycling requirements. Trials have shown that it is relatively easy to compound magnetite into a PP matrix and to use injection moulding with the resultant compound. Mechanical property data are presented. Pahl and Miklos [3] state that one of the driving forces behind PP acceptance by car designers is its ‘monomaterial construction’. For example, instrument panel parts and fascias can include a long glass ibre PP (LGF-PP) for the structure and a talcilled a PP for ductwork and a thermoplastic olein (TPO) for the outer skin. One recent advancement in LGF-PP is the Verton MTX concentrate. The heat-stabilised masterbatch is 75% LGF by weight and is available in 13 and 25 mm long pellets. It is speciically formulated for machine-side blending using neat PP. Verton MTX is based on a commingled ibre technology called Twintex from Saint-Gobain Vetrotex America. Pahl and Miklos compared the performance properties of a fully compounded heat-stabilised 30% LGF-PP to a 75% LGF-PP masterbatch diluted to a comparable 30% glass ibre ill. The tests helped to verify that the key performance properties were not compromised by the masterbatch approach. Engineering polymers, such as PP can be reinforced at the macroscopic level with a variety of higher modulus materials such as ibres, beads, and cement, to form heterogeneous composites [4, 5]. Thus, reinforcing PP with glass ibres as a co-woven mat has many advantages. Alternatively, reinforcement can also take place at the molecular level. These researchers have reported on the beneits of simultaneous

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Engineering Plastics molecular and macroscopic reinforcement. Low fractions of polymer liquid crystal interlayers increase the damping energy and also increase the glassy plateau modulus. Long-term dimensional stability is mainly inluenced by the presence of the woven glass ibre fraction in the co-woven mat. However, higher loadings of polymer liquid crystal interlayers have detrimental effects on the dimensional stability, causing interply slip at lower temperatures. The beneits of using a polymer liquid crystal interlayer, inter-ply between the co-woven mats are mainly associated with the weight savings to be gained by using a material with a lower speciic gravity. The crystallisation kinetics of the composites are affected by the nucleating effects of the polymer liquid crystal interlayer and the glass ibre. When both components are present the glass ibres dominate the nucleation kinetics. This is also relected in the degradation kinetics, where complete degradation of the matrix occurs at lower temperatures for the glass reinforced materials. Basell (USA) [6] have reported on the development of a family of high-density polyethylene (HDPE) resins which have a high resistance to bio-diesel fuels and it is currently being developed for use in automotive fuel tanks. Exposure of fuel tanks to biofuel for 11 years at 40 °C has, to date, produced no signiicant deterioration of the polymer properties and it is signiicantly better than the deterioration that occurs with current low-density polyethylene (LDPE) grades used in fuel tanks. Polyethylene (PE), PP and ultra-high molecular weight polyethylene have been used in gears at lower temperatures in aggressive chemical and high wear environments [7].

6.1.2 Ethylene-propylene-diene Ethylene-propylene-diene terpolymer (EPDM) is a rubbery polymer which has been applied to polymeric composites for automotive window seals which are generally exposed to complex service environment conditions [8]. Different EPDM rubber compounds (control, bulk modiied and surface modiied), coated with polyurethane were exposed to controlled ultraviolet (UV) irradiation. The higher the adhesion, the lower the extent of UV penetration through the interface was. The photooxidation mainly takes place from the surface, as the energy gets consumed and the intensity of the UV decreased on its passage through the strongly adhered layers to the rubber compound. The coating layer, being on the surface, is more affected and photodegraded by the UV irradiation than the rubber compound. The sample being multi-phasic in nature and with a strong interface, can scatter the UV strongly and thus shows the best weatherability among all the systems.

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Plastics in Automotive Engineering Delaval and co-workers [9] examined the effects of two pollutants (engine oil and ethylene glycol) and recycling on the thermal and rheological properties of two talc containing PP-based materials used in the automotive industry. The PP-based materials were a copolymer of PP and ethylene-propylene rubber (EPR) used for front bumper face bars and PP-EPR-talc used for back bumper face bars. The results showed that the pollution and recycling did not decrease the intrinsic properties of these PP-based materials. Indeed the presence of engine oil improved the thermal stability, indicating that engine oil may act as a lame retardant in this particular case.

6.1.3 Polyether Ether Ketone Hufenbach and co-workers [10] and researchers at LNP Engineering Plastics [11] have discussed the use of polyketones in engineering plastics. This included a study of the damage to high speed impellers in fabricated carbon ibre reinforced PEEK. Researchers at LNP Engineering Plastics [11] have developed a series of formulations of aliphatic ketone based, thermoplastic compounds containing glass and carbon ibre reinforcement and polytetraluoroethylene as a lubricant. These polyketones are targeted at the automotive market and are characterised by good impact performance over a broad temperature range and also high chemical resistance, good hydrolytic stability and superior resilience.

6.1.4 Polyesters Krigbaum [12] has reported on the use of glass ibre reinforced composites, both from Cytec Industries, based on Cyglas 685 unsaturated polyester [bulk moulding compound (BMC)] and Cyglas 695 vinyl ester resin (BMC) in automotive valve covers and other engine cover applications. The recycling of these valve covers is also discussed.

6.1.5 Polyethylene terephthalate Polyethylene terephthalate (PET) usually incorporating glass ibre reinforcement has been used extensively in automotive body mouldings, bumpers and housings [13-15]. Sepé and co-workers [13] found that automotive components consisting of a metal insert over-moulded with impact modiied glass ibre reinforced PET cracked adjacent to the insert following thermal shock testing (100 cycles at – 40 to 180 °C). The melt low index of the material increased by 140% on drying prior to moulding,

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Engineering Plastics suggesting a molecular weight reduction because of polymer degradation. However, the intrinsic viscosities before and after drying, and after moulding were similar, indicating minimal degradation. This anomaly was attributed to the melt viscosity and intrinsic viscosity techniques being more sensitive to low molecular weight fractions and high molecular weight fractions, respectively. Gel permeation chromatography measurements conirmed a bimodal molecular weight distribution, the bimodal nature of which increased with increasing exposure to elevated temperatures. Gobernado and co-workers [14] have discussed the use of PET to produce thermally bonded vehicle roof liners by thermoforming. Renaud [15] has reviewed developments by the DuPont European Technical Centre in the design and production of automotive components using advanced blow moulding techniques. Examples are presented of automotive hoses manufactured in DuPont’s engineering plastics and Hytrel polyesters elastomers. PBT gears have extremely smooth surfaces and have a maximum operating temperature of 150 for unilled and 170 °C for glass reinforced grades. PBT works well against polyacetals and other plastics as well as against metal and is utilised in engine housings [7].

6.1.6 Polyamides Various PA, particularly PA 6 and PA 6,6 have been used in the manufacture of parts for automotive applications including radiator tanks [15-20], engine covers in Audi cars [20-22], a pedal box [23] and various other components [24-26]. Usually glass ibre reinforcement is included in the formulations [27, 28]. The requirements for radiator tanks are good heat stability, vibration resistance and resistance to coolant additives [18]. Audi use 25% glass ibre, 15% mineral reinforced Nylon 6,6 for the fabrication of rubber covers for their Audi A4 and VW Passat engines. These covers have good dimensional stability even at elevated temperatures, which ensures a low creep tendency that contributes to a long in-service life of the part [27]. Di Pasquale and co-workers [29] have discussed the recycling of glass reinforced PA 6,6 used in the automotive industry. DSM Engineering Plastics [30] is developing a high performance PA 4,6, called Stanyl for the production of tumble valve bearings and chip carriers for the latest generation of Mercedes Benz V6 and V8 engines. Resistance to high loading, good wear and friction properties play an important role in the lifetime of this component.

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Plastics in Automotive Engineering Tumble valve bearings are an integral part of the manifold optimising air low in the combustion chamber. It is the irst time that such tumble valves have been produced by assembly moulding and, according to DCM, Stanyl played an important role in making this possible. With the in-mould assembly technique, components are assembled inside the mould in a two shot (2K) process. This results in signiicant cost savings compared to traditional processes in terms of assembly, tooling and machinery [31]. For in-mould assembly to work a combination of materials is required which can meet both the in-mould process demands as well as the performance under the operating conditions throughout the life of the engine. In the moulding process, says DCM Engineering, Stanyl has outstanding stiffness at high temperatures – even close to its melting point – which enables 2K over-moulding without distortion of the initial moulding. As the assembly has a bearing function, free movement of the two components is required after production. This requires that no adhesion occurs between the two materials during the moulding process and the shrinkage coeficients are such that free movement is maintained after moulding and at engine operating conditions and temperatures up to 150 °C. In addition, wear and friction behaviour of the component materials is very important. The tumble valve bearings have to resist high loads. Good wear and friction properties play an important role in the lifetime of the component itself and subsequently of the engine. A grade, selected from the Stanyl portfolio of materials that are optimised for stiffness and improved tribological performance, gave the correct performance against the PPS mating material in the assembly [31].

6.1.7 Polyacetal A polyacetal, Delrin 300CP, from DuPont Engineering Polymers (Wilmington, DE, USA) [6] combines high impact and mechanical performance with high low, which improves weld-line strength. Its cost is equivalent to standard grades. Delrin 300CP is designed for use in automotive fasteners, as seat-belt components, levers, brackets, and hardware for window and doors. Delrin 300CP offers consistent impact performance over a broad temperature range. For example, notched Charpy impact of 10.5 kJ/m2 at 23 °C only falls to 10 kJ/m2 at 30 °C. High elongation at yield (22%), high stiffness (440 MPa) and high creep resistance help extend the use of the products in continuously loaded, spring-elastic components. Use of polyacetal gears is increasing because of their high performance, dimensional stability, high fatigue, chemical resistance at temperatures up to 90 °C, and excellent lubricity against metals and plastic materials in automotives and precision gears [7].

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6.1.8 Polyphenylene Sulfide A 40% glass ibre reinforced PPS is used in for automotive fuel rails [28]. This engine component conveys fuel from the injection pump to the cylinders and is required to withstand rapid changes of pressure, service temperatures of up to 120 °C, engine vibrations, and direct contact with aggressive fuels. Details are given of the chemical resistance tests carried out on the Fortron grade and also on a branched PPS grade and two PA 6,6 grades. Test fuels were ASTM reference fuel C, two aggressive fuels with differing methanol proportions, and an auto-oxidised fuel containing peroxide and copper additives. Fortron 1140L4, a linear partially crystalline PPS, exhibited the highest impact resistance and dimensional stability. PPS offers high stiffness, dimensional stability, and fatigue and chemical resistance at temperatures as high as 200 °C. It is used in demanding automotive applications. Liquid crystalline polymers such as thermoplastic elastomer copolyesters are being used in lower power, higher speed gears because it allows them to tolerate inaccuracies and reduce noise while providing suficient dimensional stability and stiffness [7].

6.2 Acoustic Properties of Polymers Treny and Duperray [32] have pointed out that issues of human comfort relating to noise and vibration are one of the major priorities for materials structural research and development in the ield of transportation. Dynamic mechanical analysis (DMA) testing provides a way to characterise in an accurate manner the viscoelastic properties of all the material used in vehicle interiors. Using a unique database software allowed easy material selection according to their viscoelastic properties. An approach for the optimisation of materials through the combination of selective database software and speciic numerical calculation methods, to predict the inal acoustic behaviour during the materials selection and systems development period are presented. A further consideration in sensory studies is the evaluation of tactile properties of automotive components reported by Giboreu and Bardot [33]. Plastic covers for gasoline and diesel engines have become generally established [34]. The trend is towards the use of increasingly high-quality, multi-functional designs. Modern engine covers typically feature combinations of different materials and surface inishes and integrate widely diverse functions such as sound deadening. Blinkhorn and co-workers [35] developed a new glass ibre reinforced PP substrate for use in car interiors as a semi-structural and acoustic material. It is available in a number of weights per unit area and with various proportions of glass. The composite

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Plastics in Automotive Engineering is claimed to have exception expansion properties, which allow components of varying thickness to be moulded. Palmer [36] discusses Thinsulate™ sound absorbing materials made by 3M for the automotive sector. These materials have enabled design engineers to totally rethink their approach to acoustic absorption in many areas of motor vehicles. Janisch and co-workers [37] and Browell and Jyawook [38] studied the acoustic properties of automotive weather sealing using a thermoplastic vulcanisate for body sealing applications. EPDM sponge was compared with JyFlex (thermoplastic vulcanisation). The study was performed using multiple acoustic tests (road noise and component noise), supported by inite element analysis as a diagnostic tool. It was shown that primary seal acoustic performance is stiffness controlled at low frequencies and mass controlled at higher frequencies. A series of studies are reported which demonstrate the extent of the acoustic advantage by using higher density material for automotive weather strip sealing applications.

6.3 End of Life of Vehicles The automotive industry faces worldwide pressure to help ind environmentally friendly ways of disposing of end-of-life vehicles [39]. Most national governments have some form of proposed legislation to cover vehicle disposal and the European Union has designated vehicle scrap as a priority waste stream. There are questions of economic viability, environmental balance and lowest energy use, which must be considered, alongside the necessity to satisfy other legal and customer requirements. Cost estimates for the recovery and recycling of plastic material tend to ignore the time and cost associated with identifying the material. Most dismantling studies start with a knowledge of the materials that make up the parts to be removed. In practice the cost of material identiication by non-automated systems, such as referring to dismantling manuals or inding and reading material identiication marks, may well tip material recycling into the non-economical category. Mistakes in material identiication can also have serious consequences on the later stages of the recycling process, where contamination by non-compatible polymers can ruin whole batches of recylate. The development of two different types of automated material identiication equipment is described together with some of the other techniques evaluated during the development process. Viera [40] has discussed the reuse of the waste produced from edge trimming in the extrusion of TPO sheets and inal inspection of TPO skin/crosslinked PE (XLPE) foam laminates. Different analysis techniques were used to evaluate the effects of the recyclate on the inal product performance. The DMA results show no signiicant

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Engineering Plastics changes of the viscoelastic properties for different percentages of recylate. Adding TPO/XLPE foam scrap into the virgin TPO causes a signiicant increase in viscosity of the compound. Results from oxidation induction time measurements show that over 50% of recycled material may cause some failure in the thermal stability of the compound. Therefore, recycled TPO skin can be reutilised for the sheet extrusion process, without affecting the functionality and quality of the inal product performance. The incorporation of TPO/PE foam laminates into some injection moulding applications has proved to be a cost effective way of improving impact resistance plastic applications of the car, such as the wheel arch cover.

6.4 Miscellaneous Applications

6.4.1 Interiors Traugott and co-workers [41] have discussed the emergence of thermoplastics as primary material choices in automotive interiors. This brings numerous challenges. Increasingly, cost and performance balances are closely scrutinised to maximise the value for the consumer. Careful comparisons and rapid material development aid applications calling for structural rigidity and impact resistance. Great importance is placed on the ability of automotive thermoplastics to be fabricated with durable, low gloss irst surfaces. This requirement motivates the development of advanced fabrication processes, mould designs (including grain) and materials. Traugott and co-workers [41] place the emphasis on aspects of PP, acrylonitrilebutadiene-styrene (ABS) and polycarbonate (PC) blends with ABS or impact modiiers. Material development beneits from a host of recent technical advancements such as catalysis, reaction engineering, impact modiication and compatibilisation. Some examples of these are fourth generation Ziegler-Natta and metallocene polyolein catalysts, highly eficient solution processes (PP and ABS) and copolymer modiiers.

6.4.2 Seals Leone and Oliver [42] have discussed the applications of luoroelastomers, nitrile rubber (NBR) and hydrogenated NBR in seals for automotive air-intake manifolds. They review the properties required for such seals including mechanical and low temperature properties, heat and fuel resistance, and design requirements for the seals used in conjunction with the engineering plastics components in this application.

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6.4.3 Tyres ‘Smart’ or ‘intelligent’ tyres, equipped with under-tread sensors are capable of measuring tyre forces directly [43]. Supplied with this information rather than having to presume or infer it, a new generation of suspension, brake and stability control systems promise iner control over vehicle dynamics than has been possible before. However, just as engine performance is not determined solely by engine management electronics, so the fastest microprocessors and cleverest software can only do so much to inluence ride, braking and handling. They may exploit the tyre better, but the tyre itself still determines the ultimate performance envelope, and a great deal more besides. It is not possible to make a tyre run-lat using electronics, or lower its rolling resistance, or increase its load rating, or alter its packaging ramiications. For progress in these areas the tyre itself, and ultimately both tyre and rim, must be examined.

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Engineering Plastics 11. Plastics and Rubber Weekly, 1997, 1698, August, 13. 12. R.S. Krigbaum, Composites Plastiques Renforces Fibres de Verre Textile, 1997, 22, July/August, 60. 13. M.R. Sepé, J.A. Jansen and M.K. Kosarzycki in Proceedings of the 60th SPE ANTEC Technical Conference, San Francisco, CA, USA, 2002, Paper No.204. 14. I. Gobernado, J.C. Merino and P. Soto, Revista de Plasticos Modernos, 2000, 79, 525, 313. 15. M.C. Renaud, Revista de Plasticos Modernos, 2001, 81, 538, 444. 16. Plastiques Flash, 1997, 294/295, January/February, 54. 17. R. Schouwenaars, S. Cerrud and A. Ortiz, Composites Part A: Applied Science and Manufacturing, 2002, 33, 4, 551. 18. Plastics and Rubber Weekly, 1984, 1063, 25. 19. A.S. Lunin, T.V. Ponomareva and O.B. Lunina, International Polymer Science and Technology, 2002, 29, 5, T/52. 20. European Plastics News, 2001, 28, 8, 64. 21. Plastics and Rubbers Weekly, February 1997, 1674, 7. 22. Plastics Additives and Compounding, 2001, 3, 7-8, 14. 23. M. Youson, Engineering, September 1999, 240, 8, 50. 24. Plastiques Flash, 1998, 307, May/June, 70. 25. I. Linazisoro, Plast’21, 1996, 49, February, 50. 26. Revisita de Plasticos Modernos, 2002, 83, 549, 283. 27. T. Malek and B. Koch, Revista de Plasticos Modernos, 1999, 78, 518, 164. 28. Fortron for the Fuel Rail, Hoechst AG, Frankfurt am Main, Germany, 1999. 29. G. Di Pasquale, A.D. La Rosa, A. Recca, S. DiCarlo, M.R. Bassani and S. Facchetti, Journal of Materials Science, 1997, 32, 11, 3021.

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Plastics in Automotive Engineering 30. Plastics Technology, 2009, 55, 1, 23. 31. S. Ottewell, European Chemical Engineer, 2007, December, 40. 32. C. Treny and B. Duperray in Proceedings of the SPE ANTEC’97 Conference, Toronto, Ontario, Canada, 1997, Volume 3, p.2805. 33. A. Giboreau and A. Bardot, Revue Generale de Caoutchoucs et Plastiques, 2000, 77, 789, 43. 34. T. Zipp and H. Schmidt, Kunststoffe Plast Europe, 2000, 90, 3, 36. 35. A. Blinkhorn, L. Barsotti, T. Cheney, E. Haque and G. Knoll, International Polymer Science and Technology, 2006, 33, 10, T/1. 36. D. Palmer, Eureka, 2005, 25, 5, 14. 37. R. Janisch, S. Jyawook, J. Browell, M. Steward and R. Richardson in Proceedings of the 9th International Rapra Technology Conference on Thermoplastic Elastomers, Munich, Germany, 2006, Paper No.7. 38. J.T. Browell and S. Jyawook in Proceedings of the 65th SPE ANTEC Conference, Cincinnati, OH, USA, SPE, 2007, p.900. 39. D.F. Gentle in Plastics in Automotive Engineering, Eds., H.G. Haldenwanger and L. Vollrath, Carl Hanser, Munich, Germany, 1994, p.261. 40. C. Vieira in Proceedings of the ARC 2000 Conference: Where Innovative Ideas Merge with Reality, Dearborn, MI, USA, 2000, p.7. 41. T. Traugott, L. Novak and G. Meyers in Proceedings of the SPE Automotive TPO Conference, Troy, MI, USA, 1999, Paper No.30. 42. P. Leone and P. Olivier, Revue Generale de Caoutchoucs et Plastiques, 1998, 75, 770, 69. 43. K. Howard, Tire Technology International, 1999, September, 42.

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Plastics in Aerospace

7.1 Applications Some of the applications of plastics in aerospace engineering are listed in Table 7.1.

Table 7.1 Aerospace applications of plastics Polymer Epoxy, Kevlar prepeg Epoxy resins, carbon ibre reinforced PEEK PEEK, 20% glass ibre reinforced PEEK, 30% glass ibre reinforced PEEK, 40% glass ibre reinforced PI Polyamide-imide Polyether sulfone, 30% glass ibre reinforced PSU, 10% glass ibre reinforced PSU, 30% carbon ibre reinforced Polyvinyl luoride PEEK: Polyether ether ketone PI: Polyimide PSU: Polysulfone Source: Author’s own iles

Applications Aerospace applications Aerospace applications - fuselages, helicopter blades Aerospace applications Aerospace applications Aircraft and missile noses cones Structural aerospace applications Parts of aerospace engines Jet engine parts Nose cones Aerospace applications Aircraft exterior and interior components Aircraft interiors

It is seen that many of these formulations are available in glass ibre or carbon ibre reinforced forms. Thus, polyether ether ketone (PEEK) is available in a 30% carbon ibre or in 20 or 30% glass ibre reinforced forms. Similarly, polysulfone (PSU) is available in a 30% carbon ibre or 10% glass-reinforced form.

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7.2 Glass fibre Reinforced Plastics The aerospace industry has long recognised the major beneits associated with using ibre reinforced composite materials [1]. The more popular techniques available for composite production are the traditional wet lay-up or autoclave and resin transfer moulding. Efforts to further reduce processing time and improve part quality have focused on improved process control. To date this has been based on offline techniques. The need for on-line cure monitoring was recognised and suitable in-mould sensors were developed. The Engineering Composites Research Centre has investigated and concentrated on the speciic problems encountered in the aerospace industry. Of the available cure monitoring methods, parallel plate dielectric analysis offered the greatest potential for determining the through-thickness cure state of the resin during cure. A laboratory dielectric instrument was used to simulate resin transfer moulding and autoclave cure cycles for composite structures containing non-conductive and conductive ibres and for different resin systems used in the aerospace industry. Key resin cure stages were identiied by an appropriate dielectric signal and correlated with data from other thermal and mechanical techniques. Insulated parallel plate dielectric sensors were developed for use in the laboratory instrument with the potential for incorporation into composite production tooling. Buehler and co-workers [2] found that several prepreg materials from different suppliers meeting the same airplane material speciications were found to yield cured parts of various quality levels even when they were fabricated according to the standard processing methods. While the speciications dictate the mechanical properties of the cured structure and some physical properties of the prepreg material, they place few requirements on handling and manufacturing behaviour. Some parts, such as honeycomb structures, experience core crush and several have a high level of porosity. Because of these defects the parts are rejected and thus, manufacturing cost is increased. In addition, these parts can also result in some service-related problems, especially water ingression problems due to skin porosity. Accordingly, the main focus was to develop a better understanding of the physical characteristics of prepreg systems and to identify the appropriate evaluation procedures required to reduce the number of rejected parts. Four glass ibre commercial prepreg materials, which had been cured at 121 °C from different suppliers but corresponding to the same material speciication were evaluated by various techniques and methods. These include test methods such as resin content, gelation time, volatile content and resin low. Additional evaluation techniques, such as Fourier-Transform infrared and thermal analysis, were also incorporated, and comparison to similar prepreg systems was also included. Handling properties and manufacturing behaviour were evaluated by measuring prepreg tack and frictional resistance. Special emphasis was placed on correlating prepreg properties with inal part quality to identify key prepreg characteristics necessary to guarantee the manufacture of high quality parts.

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Plastics in Aerospace Roy and co-workers [3] investigated thermal transport phenomena in ibre reinforced composites, composite joints and the composite material interface. It was shown through inite element analysis and molecular dynamics simulations that interface impedance plays an important role in dictating the thermal transport through the interface and that through materials modelling, parameters can be identiied to guide the processing for tailoring the interface performance.

7.3 Carbon Fibre Reinforced Nanocomposite Plastics Earlier research [4-6] was concerned with the mechanical and thermal properties of carbon ibre reinforced nanocomposite plastics. Patton and co-workers [6] reported on the ablation, mechanical and thermal properties of vapour grown carbon ibre (VGCF)/phenolic resin (Pyrograf® III from Applied Sciences Inc./Durite®SC-1008 from Borden Chemical Inc.) composites. These were evaluated to determine the potential of using this material in solid rocket motor nozzles. Composite specimens with varying VGCF loading (30−50 wt%) including one sample with ex-rayon carbon fibre plies were prepared and exposed to a plasma torch for 20 seconds with a heat flux of 16.5 MW/m2 at about 1,650 °C. Low erosion rates and little char formation were observed, confirming that these materials were promising for use as rocket motor nozzle materials. When fibre loadings increased, mechanical properties and ablative properties improved. The VGCF composites had low thermal conductivities (about 0.56 W/m-K) indicating that they were insulating materials. If a 65% fibre loading in VGCF composites could be achieved, then ablative properties were expected to be comparable with or better than the composite material, which was used on the Space Shuttle Reusable Solid Rocket Motor. The first mention of the use of carbon fibre nanocomposites in aircraft construction was in 2004 when aircraft designers began to take advantage of the high strengthto-weight ratio associated with composites by replacing aluminium parts with others made from the newer materials [7]. In today’s F-22 fighters, carbon fibre composites form nearly one-third of the jet’s structure. Composites have been adopted in terrestrial applications rather slowly. The primary obstacles have been the high cost of the materials and the labour-intensive operations and expensive fabrication equipment needed to process them. Scientists at the Air Force Research Laboratory at Wright Patterson Air Force Base have studied nanocomposites, to determine ways of modifying the polymer composites with nanoscale materials to produce composites that exhibit unconventional combinations of properties. McConnell [8] has described how in the field of complex, high-performance aerospace components, carbon fibre/epoxy composites are able to meet the multiple-functional

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Engineering Plastics requirements at prolonged service temperatures of up to 121 °C and how they can withstand short-duration spikes up to 204 °C. However, design goals for space vehicles, new commercial aircraft and ifth-generation military ighters have pushed sustained service temperatures into the range of 316−538 °C or more, well beyond the capabilities of epoxies. McConnell discusses the progress in the formulation and processing of the earliest and most widely used of the high-temperature alternative, namely the polyimides (PI). A few years ago, these high-temperature materials were still in the early stages of development. Since that time polymeric research and system commercialisation have progressed significantly. The need for reduced weight provided the primary impetus for producing cost-effective, raw materials. This led to the development of processes to ensure eventual production deployment. That deployment is now under way on flight-critical components in high rate production at McConnell and other companies. Thirty years ago, the first PI were formulated in the US Air Force and the National Aeronautics and Space Administration (NASA) funded programs. These polymerised monomeric reactant (PMR) resins based on aromatic dianhydride ester acid and aromatic diamine chemistry were polymerised through solvent addition, and eventually became the aerospace industry standard PMR 15 and PMR II-50 formulations. Carbon fibre/PMR composites outperformed metals because of their greater strength-to-weight properties in aircraft engine nozzles and nacelles, helicopter gear cases and missile fins when operating in the range of 242−342 °C. Although they are still in use today, PMR resins contain methylene dianiline (MDA) a hazardous compound and suspected liver carcinogen. About 80% of the composite parts made with PMR are autoclave cured with the balance being compression moulded. Several formulations have been developed as alternatives to PMR by scientists at NASA’s Langley R&D Centre (Hampton, VA, USA) and at NASA’s Glenn Research Centre (Cleveland, OH, USA). One of these resins, RP-46 was patented in 1991, and offers similar chemistry but uses a different diamine (3,4ʹ-oxydianiline) to reduce toxicity. RP-46 resin has a glass transition temperature of 393 °C and it demonstrates particularly high corrosion resistance in composites. An alternative to PMR, is offered commercially by the resin supplier and NASA licencee, Moltech Corporation (Blue Ash, OH, USA). Its formulation replaces MDA with 2,2ʹ-dimethyl benzidine and it can endure service temperatures in carbon fibre composites as high as 335 °C. NASA developed another resin based on phenylethynyl terminated PI oligomers for use as engine components. Further improvements in polymerised monomeric reactants were achieved by end capping the ethynyl terminated imide with resin precurser agents such as

176

Plastics in Aerospace 4-phenylethynylphthalic anhydride or biphenyl dianhydride based PI which offer toughness and lexibility up to 316 °C in carbon ibre nanocomposites. Newer carbon nanocomposite PI formulations have even higher service temperatures up to 816 °C with high lexural strength.

7.4 Pitched Fibre Cyanate Ester Composites It was announced in 2002 that the Mercury Surface, Space, Environment, Geochemistry and Ranging (MESSENGER) spacecraft would be the irst spacecraft to orbit the planet Mercury [9]. Designed and built by the Johns Hopkins University’s Applied Physics Laboratory (APL), the spacecraft will orbit the planet for one year. In order to reduce the costs of this NASA Discovery Mission, the solar arrays needed to be constructed of conventional, space-qualiied materials. System thermal, mass and stiffness requirements dictated that the panel facings be fabricated from a high thermal conductivity and stiffness pitch ibre composite material capable of withstanding shortterm temperatures as high as 270 °C. A toughened, cyanate ester composite material resin system which was cured at 177 °C was chosen, with a post-cure used to extend the glass transition temperature closer to the maximum predicted temperature. A lengthy development program was conducted at APL to provide assurance that the materials and processes chosen were capable of performing under such a demanding thermal environment [10]. The results of this programme will be applicable to other high temperature spacecraft applications, which use advanced pitch ibre cyanate ester composite structures. Loos and co-workers [11] have discussed the use of a carbon ibre uni-weave fabric with a tackiier coating as a potential replacement for tailored composite aerospace structures. The ibre was impregnated with epoxy resin and oven cured. Composite laminates that were fabricated using the modiied process. These had higher mechanical properties than the composite laminates fabricated using a traditional process.

7.5 Recent Developments In 2007 Boeing launched their Boeing 787 Dreamliner in which pre-impregnated carbon ibre is used for polymer-matrix composite structural components [10]. Toughened polyacrylonitrile-based ibres and other polymeric construction materials were used. The Boeing 787 contains about 50% by weight of plastic components including nose, fuselage, wing box, landing gear, horizontal stabilisers, passenger doors, wing tips, ice protection system, windows, nacelle, tail assembly and hydraulic clamps.

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Engineering Plastics The Boeing 737 Dreamliner utilises carbon ibre reinforced epoxy resin composite in its construction (Figure 7.1).

Figure 7.1 Boeing 737 Dreamliner

In 1994 an Airbus 380 belonging to American Airlines crashed. Golfman [13] carried out an investigation into the accident. Investigators focused on air turbulence as a possible factor in the crash of the American Airlines Flight 587. This plane appears to have lown through the wake of a large plane that was much closer than originally thought. This lead to a failure due to general micro-buckling otherwise known as ibre kinking, which generally occurs, in part, due to incomplete curing of the epoxy resin, or, to a deiciency in the hardening agent during the manufacturing process. Separately the National Transportation Safety Board conirmed that the plane, which crashed after losing tail pieces and both engines, was the same Airbus A300 that ran into heavy turbulence in 1994. Structural experts checked it to determine, whether the aluminium and plastic composite materials that were part of the tail assembly had been weakened by microscopic cracks and then broken by a later event. The purpose of this research was to investigate the dynamic stability of the leading/trailing panels and avoid parametric resonance. Studies of the leading/trailing panels as part of the tail structures considered that in cases of turbulence, the left load will be signiicant

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Plastics in Aerospace increased. In the case of loss stability the free and force vibration frequencies will occur at the same time. Carbon ibre/epoxy composites are used extensively in the A380 Airbus composite structures to reduce the weight ratio and costs. Using a lightweight carbon ibre composite airframe instead of an aluminium shell improves the vibration conditions. The vertical leading edge section and the trailing edge panels are a sandwich construction with a honeycomb core and glass ibre/epoxy prepreg skins. The single piece composite rudder is assembled into a hollow triangle from three honeycomb sandwich panels with carbon ibre/epoxy skins. The main failure mode of a leading edge panel attached fuselage includes both the bending of structure and the failure due to general buckling. It was shown in this investigation that the conical lattice structures were not stable. The failure was due to micro-buckling. Micro-buckling generally occurs because of a weak matrix, which is due in part to the epoxy not curing completely or a deiciency of hardening agent during the manufacturing process. Frequencies of force and free vibration are shown, in Figures 7.2 and Figure 7.3, respectively.

600 400 200 0 1:02 1:02 1:02 1:04 1:04 1:04 1:08 1:08 1:08 1/2.5 1:05 1:10 1/2.5 1:05 1:10 1/2.5 1:05 1:10 Various geometrical parameters and compression loads Series 1

Series 2

Figure 7.2 Boeing Airbus - Frequencies of force vibrations of heading trailing panels of carbon ibre/epoxy composites. Reproduced with permission from Y. Golfman, Journal of Advanced Materials, 2010, 42, 1, 28. ©2010, SAMPE [13]

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Frequencies

Frequencies of free vibrations the leading/trailing panels 1200 1000 800 600 400 200 0

1/2.5 1:05 1:10

1

2

3

Coefficient of chord to height relation

Figure 7.3 Boeing Airbus - Free vibrations of carbon ibre/epoxy composites. Reproduced with permission from Y. Golfman, Journal of Advanced Materials, 2010, 42, 1, 28. ©2010, SAMPE [13]

References 1.

A.T. McIlhagger, S.T. Matthews, D. Brown and B. Hill in Proceedings of the IOM CAC-99 Conference, Bristol, UK, 1999, p.133.

2.

F.U. Buehler, J.C. Seferis and S. Zeng, Journal of Advanced Materials, 2001, 33, 2, 41.

3.

A.K. Roy, S. Sihn, S. Ganguli and V. Varshney in Proceedings of the SAMPE Technical Conference - Multifunctional Materials: Working Smarter Together, Memphis, TN, USA, 2008, Paper No.44.

4.

Advanced Materials and Processes, 2002, 160, 5, 13.

5.

Proceedings of the 20th SAMPE Technical Conference, Minneapolis, MN, USA, 1988.

6.

R.D. Patton, C.U. Pittman, L. Wang, J.R. Hill and A. Day, Composites Part A: Applied Science and Manufacturing, 2002, 33, 2, 243.

7.

M. Jacoby, Chemical and Engineering News, 2004, 82, 35, 34.

8.

V.P. McConnell, High-Performance Composites, 2009, 17, 4, 39.

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Plastics in Aerospace 9.

P.D. Wienhold and D.F. Persons in Proceedings of the 34th SAMPE Conference - Materials and Processing – Ideas to Reality, Baltimore, MD, USA, 2002, p.308.

10. R. Renstrom, Plastics News (USA), 2007, 19, 18, 4. 11. A.C. Loos, B.W. Grimsley, R.J. Cano and P. Hubert in Proceedings of the SAMPE 05 Conference: New Horizons for Materials and Processing Technologies, Long Beach, CA, USA, 2005, Paper No.175. 12. C. Christ, High-Performance Composites, 2001, January/February. 13. Y. Golfman, Journal of Advanced Materials, 2010, 42, 1, 28.

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Other Engineering Applications

In addition to their use in specialised applications as discussed in earlier chapters, a variety of plastics are used in many general engineering applications such as gears, bearings and so on, some of which are listed in Table 8.1.

8.1 General Engineering Applications As shown in Table 8.1 plastics are used in gears, bearings, bushes, cogs, cams, sprockets, gaskets, valve seals, pump impellers, piston rings, pipes and hoses, compressors, valves, pumps, wear pads and O-rings.

Table 8.1 General engineering applications of plastics Application Gears

Plastic UHMWPE PMMA POM, 30% glass ibre reinforced, PTFE, lubricated POM, 30% carbon ibre reinforced POM, 2% silicone lubricated PBT, 2% silicone lubricated PET, 30−55% glass ibre reinforced PA 6 PA 6,6 PA 6,9 PA 6,10, 10–30% glass ibre reinforced PA 11 PA 11, 30% glass ibre reinforced PA 6,12, 2% silicone lubricated PA 6,12, 20% PTFE lubricated PA 12, 30% glass ibre reinforced PA-ABS alloy PI

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Bearings

Bushes

Cogs Cams

Sprockets

184

PEI, 10% glass ibre reinforced PAI PAI, glass ibre reinforced PU thermoplastic elastomer PPS, 20% PTFE lubricated Ethylene tetraluoroethylene, 10 and 30% glass ibre reinforced UHMWPE PEEK, 2% carbon ibre reinforced POM POM, PTFE lubricated POM, 30% glass ibre reinforced POM, 30% carbon ibre reinforced POM, 2% silicone lubricated PBT, 2% silicone lubricated PA 6, MoS2 lubricated PA 6,10, carbon ibre reinforced PA 6,6, MoS2 lubricated PI, PTFE lubricated PAI PAI, graphite illed PU PTFE PTFE, 60% bronze illed PTFE, 15% graphite illed Ethylene tetraluoroethylene, 10−30% glass ibre illed Ethylene tetraluoroethylene, 30% carbon ibre illed PVDF PEEK, 30% carbon ibre reinforced POM, 30% glass ibre reinforced POM, 2% silicone lubricated PA 6,12, 2% silicone lubricated PA 12, 50% glass ibre reinforced PA 6 PA 6,12, 2% silicone lubricated POM, 30% carbon ibre reinforced PA 6 PA 6, MoS2 lubricated PA 6,6, MoS2 lubricated PA 6,6 PA 6,12 PA 6,10, 10−30% glass ibre reinforced PA 11 PA 6,12, 2% silicone lubricant PA 12, semi-lexible grade PET, 30% glass ibre reinforced PET, 45−55% glass ibre reinforced

Other Engineering Applications Gaskets Valve seals

Pump impellers

Piston rings

Chlorotriluoroethylene PTFE PA 6,6, MoS2 lubricated PA 6,10, 10−30% glass ibre reinforced PA 6,12, 2% silicone lubricated PI PI, PTFE lubricated PI, 25% graphite lubricated PAI Polyamide-imide Polyamide-imide, graphite illed PPS, 30% carbon ibre reinforced PPS, glass ibre and bead reinforced PPS, 40% glass ibre reinforced PSU PSU, 30% glass ibre reinforced PSU, 30% carbon ibre reinforced PSU, 15% PTFE lubricated Ethylene chlorotriluoroethylene Ethylene chlorotriluoroethylene, glass ibre illed Ethylene tetraluoroethylene Ethylene tetraluoroethylene, 10 and 30% glass ibre illed Ethylene tetraluoroethylene, 30% carbon ibre illed PVDF Fluorinated ethylene-propylene Fluorinated ethylene-propylene, 20% glass ibre reinforced PEEK, 30% carbon ibre reinforced Diallylisophthalate, long glass ibre reinforced PAI, graphite illed PSU, 30% glass ibre reinforced PSU, 30% carbon ibre reinforced PSU, 15% PTFE lubricated Ethylene tetraluoroethylene, 10 and 30% glass ibre illed PI PI, PTFE lubricated PAI, glass ibre reinforced PAI, graphite illed PTFE PTFE, 60% bronze illed PTFE, 15 and 25% glass ibre illed PTFE, 15% graphite illed Ethylene-tetraluoroethylene, 30% carbon ibre illed

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Engineering Plastics Pipes and hoses PVDF LDPE HDPE XPE PP, UV stabilised Ethylene-propylene, ire retardant Polymer resin, moulding compound PA 12, semi-lexible PSU, 30% carbon ibre reinforced PTFE Compressor PI, 25% graphite lubricated rings Valves PAI PAI, glass ibre reinforced PTFE PPS, glass ibre, bead reinforced and chlorotriluoroethylene bead reinforced PPS, 40% glass ibre reinforced PSU, 30% carbon ibre reinforced Chloroluoroethylene Wear pads PTFE, 6% bronze illed PTFE, 15−25% glass ibre illed PTFE, 15% graphite illed O-rings Chloroluoroethylene ABS: Acrylonitrile-butadiene-styrene HDPE: High-density polyethylene LDPE: Low-density polyethylene MoS2: Molybdenum disulide PA: Polyamide(s) PAI: Polyamide-imide PBT: Polybutylene terephthalate PEEK: Polyether ether ketone PEI: Polyether imide PET: Polyethylene terephthalate PI: Polyimide PMMA: Polymethylmethacrylate POM: Polyoxymethylene PP: Polypropylene PPS: Polyphenylenesulide PSU: Polysulfone PTFE: Polytetraluoroethylene PU: Polyurethane PVDF: Polyvinylidine luoride UHMWPE: Ultra-high molecular weight polyethylene UV: Ultraviolet XPE: Crosslinked polyethylene Source: Author’s own iles

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Other Engineering Applications Gears are a particularly critical application of plastics and, as such, are considered in more detail in the lowing sections. A wide range of polymers have been used for the fabrication of gears. The strongest growth area has been the automotive ield. As amenities have become central to competitive success, automakers have sought to power a variety of vehicle sub-systems with motors and gears. This has utilised plastic gears in areas ranging from lift gates, seating, and tracking headlights to brake actuators, electronic throttle bodies, and turbo controls. Plastic power gears are also used in appliances. Some larger applications, such as washing machine transmissions, have pushed the limit on gear size, and plastic is often used as a replacement for metal in these applications. Plastic gears are present in many other areas, for example, damper drives in heating, ventilation and air conditioning zone controls, valve actuators in luid devices, automatic lushers in public restrooms, power screws that shape control surfaces on small aircraft, and gyro and steering controls in military applications. A wide variety of plastics have been used in the manufacture of gears. Some of the important property requirements of gears are good fatigue, wear resistance, lubricity, rigidity for high tangential forces and toughness in shock loaded situations. Some of the more important polymers used in critical applications include polyacetals, PBT, polyamides, PPS and liquid crystalline polymers. These are the most common choices for applications such as reciprocating electrical motors. These crystalline polymers must be moulded hot enough to promote full crystallinity. Otherwise, gear dimensions can shift if the end-use temperature rises above the mould temperature and causes additional crystallisation. Acetal has been a primary gear material in automotive, appliances, ofice equipment and other applications for over 40 years. It provides dimensional stability and high fatigue resistance and chemical resistance at temperatures up to 90 °C. It has excellent lubricity against metals and plastics. PBT produces extremely smooth surfaces and has a maximum operating temperature of 150 °C for unilled and 170 °C for glass-reinforced grades. It works well against acetal and other plastics, as well as against metal, and is often used in housings. Nylons offer great toughness and they wear well against other plastics and metals, often in worm gears and housings. Nylon gears operate to temperatures of 175 °C for glass-reinforced grades and to 150 °C for unilled ones. But Nylons are unsuitable for precision gears because their dimensions change as they absorb moisture and lubricants. 187

Engineering Plastics PPS offers high stiffness, dimensional stability, fatigue resistance and chemical resistance at temperatures as high as 200 °C. It is used in demanding industrial, automotive, and other end use applications. Liquid crystal polymers offer great dimensional stability in small, precision gears. It tolerates temperatures to 220 °C and has high chemical resistance and low mould shrinkage. It has been moulded to tooth thicknesses of about 0.066 mm. Thermoplastic elastomers help gears run quieter and make them more lexible and better able to absorb shock loads. A copolyester thermoplastic elastomer, for example, is being used in lower power, higher speed gears because it allows them to tolerate inaccuracies and reduce noise while providing suficient dimensional stability and stiffness. Material speciication for gears and housings should take into account the dramatic effects ibres and illers have on resin performance. For example, when acetal copolymer is loaded with 25% short glass ibre (2 mm or less), its tensile strength more than doubles at elevated temperatures and its stiffness more than triples. The use of long glass ibre (10 mm or more) boosts strength, creep resistance, dimensional stability, toughness, rigidity, wear, and other properties even further. This makes long ibre reinforcement attractive for use in large gears and housings to give the stiffness needed and to give better control of thermal expansion. Polyethylene (PE), PP and UHMWPE have been used in gears at lower temperatures in aggressive chemical and high-wear environments. Other polymers have been considered for gears, but many impose severe limitations on gear function. Polycarbonate, for example, has poor lubricity and resistance to chemicals and fatigue. ABS and LDPE generally cannot meet the fatigue endurance, dimensional stability, and heat- and creep-resistance requirements of precision gears. Such polymers are most often found in basic, low-load or low-speed gears.

8.2 Building Materials

8.2.1 Building Insulation Researchers at Aprithan-Schaumstoff GmbH [1] devised an 'Apricell ProForm' PU resin insulating device. This product enables non-thermal bridging full-surface insulation of arched roof surfaces even in low-energy house building. It places no restrictions on the design of round roof shapes and is made from a PU high-resistance foam with an 030 heat conductivity grade. It is more economic when compared with conventional structures using intermediate or full rafter insulation.

188

Other Engineering Applications Bogdan and co-workers [2] state that the use of insulating products in the building envelope is deined by many criteria. The speciied R-value (thermal resistance) or k-factor (thermal conductivity) for the structure is an essential component of most speciications. The building industry has traditionally reported the R-value measured at a mean temperature of 23 °C to calculate insulation requirements for the building envelope. With improvements in instrumentation, it is now possible to specify insulation based upon the actual use temperatures for a given building or region. Dedecker and co-workers [3] evaluated the European standard, EN13165 (Annex C) [4] for factory produced rigid PU foam products used as thermal insulation boards for buildings. Tests were carried out on diffusion open and diffusion tight insulation boards having different thicknesses to determine their insulating capacity (lambda values in W/mK). Fresh and aged foam samples were subjected to cell gas analysis and the diffusion coeficients of the foams were determined. Lambda ageing simulation software was used to it experimentally measured short-term lambda versus time curves and to make 25-year lambda predictions and the experimentally determined lambda values were compared with the 25-year predictions. In North America, polyisocyanurate insulation is used heavily in commercial rooing applications [5]. It has high thermal resistance and good ire properties making it the best insulating choice. It has been known for a while that the initial thermal resistance of polyisocyanurate boards will change very slowly over time. Because the lifetime of such products is long, thermal ageing is caused by the diffusion of the multitude of gases, and the insulation product is not homogeneous. The polyisocyanurate industry has now identiied a test method based on a Canadian standard, CAN/ULC-S770-00 [6], which deines the long-term thermal resistance as the average weighted thermal resistance over a 15-year period. One of the objectives of this work was to compare the long-term thermal resistances predicted by this test method to those obtained from the mathematical modelling and calculation algorithms developed by Huntsman Polyurethanes.

8.2.2 Roofing Rooing applications require high performance levels in terms of thermal insulation, dimensional stability, mechanical strength, compatibility with other materials, and so on. They are therefore a severe testing ground for insulating materials. Chittolini and co-workers [7] considered different types of rooing, including application temperature, working temperature, thermal shock and examples of applications. Following the ire in 1953 at General Motors’ transmission plant (Livonia, MI, USA), it was realised that there was a need for test methods for rooing systems and the

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Engineering Plastics ‘White House’ test method and subsequent smaller test procedures for polystyrene (PS) foam were developed [8]. The General Motors’ ire involved a localised internal ire, which spread, fuelled by the roof covering assembly to eventually engulf the whole building. Details are given of a an Underwriters Laboratories (UL) test method UL 790 [9], which uses oxygen consumption calorimetry to quantify the roof covering materials’ contribution to the underdeck ire sources by capturing efluent from beneath the roof assembly and recording of the rate of heat production measured in kW/min.

8.2.3 Construction Materials Barpanda and Mantena [10] discuss the pultrusion process and describe it as a well-established technique for the cost-effective production of high modulus and lightweight composite materials having constant cross-sectional proiles. Pultruded composites are widely used as structural members, for example, as beams, trusses and stiffeners, because they have a high proportion of axial ibres necessary to sustain large tractive forces. These structural members are subjected to a combination of static and dynamic loading conditions at wide temperature ranges and over long periods. Since polymeric composites exhibit viscoelastic behaviour, the effectiveness of these materials as structural members must be thoroughly evaluated to ensure long-term stability. The dynamic performance characteristics of pultruded glassgraphite/epoxy hybrids were evaluated at room temperature and were shown to have improved. The effects of temperature, frequency, post-curing, along with the type and placement of ibres on the dynamic lexural properties of glass-epoxy and hybrid glass-graphite/ epoxy were also investigated. Emphasis was placed on the evaluation of creep and stress relaxation performance characteristics of pultruded glass-graphite/epoxy hybrid composites. Dynamic mechanical analysis was adopted for the accelerated creep and stress relaxation testing. The time-temperature superposition principle, which greatly reduces experimental time, is effectively utilised for predicting the creep and stress relaxation properties of the hybrid composites. Results indicate that the type and amount of ibres as well as their lay-up sequence plays a signiicant role in determining the low and load bearing characteristics. Thermosetting epoxy ibre composite materials are widely used for infrastructure rehabilitation and seismic retroit of concrete members. However, for rehabilitating steel structures, thermoplastic polymers offer signiicant advantages over thermosetting matrices. When bonded to steel substrates, the toughness of thermoplastic allows the material to strain under applied stresses (thermal or lexural) without compromising the metal/composite bond.

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Other Engineering Applications Love and Karbhari [11] carried out a study of HDPE/reactive ethylene terpolymer blend (RET) as a reinforcing material for thermosetting epoxy ilm reinforced polymer structure. The HDPERET blend offers high strength, resistance to moisture absorption and chemical attack, as well as good adhesion to steel substrates. The reactive component of the RET, glycidyl methacrylate, allows for compatibilisation with HDPE, acceptance of illers and ibres, and most importantly may be hot-melt bonded to steel, eliminating the need for an external adhesive. The resulting composite system was manufactured as a pre-fabricated laminate and hot-melt bonded to steel to determine its capacity for arresting crack growth in the substrate. The degree of adhesion between the composites and steel was determined via double lap-shear adhesive testing, while the composites were characterised through tensile testing. Composite blends hot-melt bonded to artiicially defective steel coupons pulled in tension gave the strengthening capability. The tensile strength and modulus of HDPE/RET composites decreased with the addition of RET. The maximum adhesion at the composite/steel interface was found when 33 wt% RET was added to the HDPE (66/33). This compositional blend offered the highest degree of rehabilitative strengthening, carrying up to 12.5% more applied load than the un-reinforced condition. Tensile properties of the HDPE/RET blend are shown in Table 8.2. The HDPE 100/0 carbon-ibre composite showed complete linear stress-strain behaviour up to its ultimate tensile strength and fracture at 10.3% strain. No deinitive fracture was seen in the HDPE blends. This is due to the interfacial de-bonding between the constituents within the polymer. The apparent loss of cohesive strength of the matrix material resulted in ibre ‘pull-out’ and interlaminar slip between the carbon-ibre plies.

Table 8.2 Tensile properties of HDPE/RET carbon fibre composites HDPE/RET (wt%)

Tensile strength (MPa)

Tensile modulus (GPa)

Strain (%) Ultimate tensile At fracture strength (MPa) 100/0 178.8 5.6 10.3 10.3 66/33 131.1 4.6 8.0 33/66 94.5 3.8 8.7 0/100 52.9 1.7 8.3 Reproduced with permission from C.T. Love and V.M. Karbhari in the Proceedings of the SAMPE 06 Conference – Creating New Opportunities for the World Economy, Long Beach, CA, USA, 2006, Paper No.235. ©2006, SAMPE [12]

Cellular corrosion of glass ibre reinforced concrete building elements is of concern in that it has a severe effect on the tensile strength of such elements. 191

Engineering Plastics

8.2.4 Wood Substitute Xanthos and co-workers [12] did some research in which LDPE was melt blended with either automotive shredder residue, carpet backing residue or mixtures of the two and prototype blocks were intrusion moulded from them. These blocks were evaluated for use as a wood substitute for the building industry by conducting tests to determine their short-term and long-term mechanical properties, lammability, thermal conductivity and heavy metal and total organic carbon leaching behaviour. The performance of these prototypes was compared with that of wood and the composites containing carpet residue were found to be favourable as replacements for wood thermal barrier components in a steel-based stud assembly.

8.2.5 Ventilation Hollow ibre and lat sheet membranes with an interfacially polymerised coating of PA have a permeance for water vapour of about 0.16 m/s [13]. These membranes can serve as a basis for building ventilation, which provide fresh air while recovering about 70% of the speciic heat and 60% of the latent heat. Because these membranes are selective for water vapour, the air is exhausted with internal pollutants such as carbon monoxide, formaldehyde and radon. The expense of the ventilator should take about three years to be recovered by reduced heating costs.

8.2.6 Earthquake Proofing Bricks are widely used in building construction as the most common building materials [14]. The heavy weight of bricks accounts for the great mass of construction and thus, makes constructions more vulnerable to damage from earthquakes. Thus, an attempt was made, to reduce the density of the bricks as well as to improve thermal insulation properties. PS foam is one of the substances that is added to the raw materials of bricks, as a pore-foaming material. The effect of PS foam type and its content in the mix and also the effect of the iring process temperature of the bricks on density, water absorption and compressive strength, were investigated and discussed. Tests showed that by increasing the PS foam additive, the compressive strength and the density of the bricks decreases, although the water absorption increases. It was necessary to specify ways for improving and optimising of the clay body so that by reducing the density, the strength of the brick is not reduced considerably. Adding even 2% of recycled PS foam keeps the compressive strength suitable for load bearing bricks.

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8.3 Plastics in Electrochemical Cells

8.3.1 Membranes Brack and co-workers [15] discussed the effect of the degree of luorination, irradiation and grafting with PS on the crystallinity and thermal degradation of some radiation grafted ilms and membranes fabricated in PVDF, polyethylene-alt-tetraluoroethylene and PTFE-co-hexaluoropropylene.The variation of the chain lengths of the grafted PS chains is a primary factor responsible for the inluence of these various parameters on the degradation process. Dweiri and Sahari [16] investigated the electrical properties of fuel cell bipolar plates of carbon-based PP composites. Combinations of carbon black and graphite lead to composites with a higher electrical conductivity. Gürsel and co-workers [17] examined fuel cell membranes with varying degrees of PS grafting that were based on alternating copolymers of ethylene and tetraluoroethylene, both crosslinked and uncrosslinked, and irradiated and sulfonated for the effects of the various processes used in their synthesis on their thermal and crystalline properties. The results obtained were compared to those from grafted membranes based on tetraluoroethylene and hexaluoropropylene. Film crystallinity was decreased by grafting and sulfonation, but melting temperatures were almost unaffected. Crosslinking slightly increased melting temperature compared to uncrosslinked ilms. Alternating copolymers of ethylene and tetraluoroethylene [16] have both been used as low conductivity membrane materials in fuel cells. A vinyl ester resin system having superior rigidity and operating temperatures up to 80 °C and high conductivity has been used in the manufacture of bipolar plates for electricity generating fuel cells [18]. Topping and co-workers [19] have shown that lithium battery membranes fabricated from a bistriluorovinyletherarylamide have excellent electromechanical stability at high electric potentials, making them potential candidates for use in battery membranes. Preliminary molecular modelling studies indicated that lithium imine enolates may play a useful role in lithium ion transport along with the crown ether linkage. Carbon/PVDF-tetraluoroethylene-propylene [20] and LiNi0.5Mn1.5O4 spinel [21] have all been used as membranes and plates in lithium ion batteries. Such membranes have excellent stability at high potentials.

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Engineering Plastics Joo and co-workers [22] have discussed a new type of composite membrane, consisting of functionalised carbon nanotubes (CNT) and sulfonated polyarylene sulfone (sPAS) for direct methanol fuel cell applications. The CNT modiied with sulfonic acid or platinum-rubidium (PtRu) nanoparticles were dispersed within the sPAS matrix by a solution casting method to give SO3-CNT-sPAS or PtRu-CNT-sPAS composite membranes, respectively. Characterisation of the composite membranes revealed that the functionalised CNT were homogeneously distributed within the sPAS matrix and the composite membranes contained smaller ion clusters than the neat sPAS. The composite membranes exhibited enhanced mechanical properties in terms of tensile strength, strain and toughness, which leads to improvements in ion conductivity and methanol permeability compared with the neat sPAS membrane, which demonstrates that the improved properties of the composite membranes induce an increase in power density. The strategy for CNT-sulfonated composite membranes in this work can potentially be extended to other CNT-polymer composite systems. Addition of functionalised CNT to sPAS as a iller improves the mechanical properties in terms of tensile strength and toughness. When compared with a neat PAS membrane, the CNT composite membranes contain more uniform and smaller ion clusters, which result in an increase in ionic conductivity and a decrease in methanol permeability. In direct methanol fuel cell (DMFC) single-cell tests Pt/Ru/sPAS exhibits a low ohmic resistance and high open-circuit voltage compared with CNT membranes, which collectively are believed to yield the highest power densities. Furthermore, unlike the sPAS membrane, Pt/Ru/sPAS has high durability as shown by sustained power density compared to cell operation time. The preparation of CNT composite membranes and their application to DMFC, as demonstrated in this work, can potentially be extended to other CNT sulfonated polymer composite systems. In particular, recent advances in the chemistry of CNT functionalisation [23] and further understanding of the interactions between CNT and polymer matrixes may lead to the preparation of a variety of new composite materials.

8.3.2 Battery Plates Proton exchange membrane fuel cells, which are commonly used in applications such as automotive, residential and portable power, contain bipolar plates [18, 24]. The aggressive environment can corrode bipolar plate materials, so the material chosen must offer excellent stability over many years of service life at temperatures of 80 °C, sometimes rising to 150 °C for brief periods. The material must also be a good conductor of electricity. BMC 940, a bulk moulding compound developed by BMCI (USA), is the material of choice for manufacturing bipolar plates. The composite is based on a special high temperature vinyl ester resin system to achieve superior rigidity at elevated operating temperatures.

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8.4 Polymers in Medical Devices A number of general articles have been published on the use of plastics in the construction of medical devices [25-30], including knee replacements [28], surgical instruments [30] and surgical batteries [29]. Polymers that are particularly suitable for the construction of medical devices include PEEK [31-33], and UHMWPE has been used in the fabrication of hip cups [34]. Gamma sterilisation does not affect the mechanical properties of PEEK and is well suited for implantable devices for humans. Green [31, 32] explains that PEEK, an exceptionally strong engineering thermoplastic, is extremely well suited to use in long-term medical implant devices. This is because PEEK is a tough material, it is resistant to abrasion and has a high impact strength and excellent lexural and tensile properties and also retains its mechanical properties even at very high temperatures. Jarman-Smith [33] discusses the increasing use of PEEK as a replacement for metal and ceramics in a variety of medical and surgical applications. He provides an overview of the properties of this material, as well as of some of its newest applications. Topics discussed include: advances in applications for the spine, advances in joint replacement, advances in trauma applications, advances in craniomaxillofacial applications, extending the properties of PEEK, and, options beyond using metal and ceramics.

8.5 Gas Barrier Properties Barrier properties in polymers are necessarily associated to their inherent ability to permit the exchange, to a higher or lower extent, of low molecular weight substances through mass transport processes like permeation. The permeation of low molecular weight chemical species usually takes place through the polymer amorphous phase and is generally envisaged as a combination of two processes, i.e., sorption and diffusion. A permeate gas is irst sorbed into the upstream face of the polymer ilm, and then, undergoes a molecular diffusion to the downstream face of the ilm where it desorbs into the external phase again. A sorption-diffusion mechanism is thus applied, which can be formally expressed in terms of permeability (P), this being the product of solubility (S) and diffusion (D) coeficients, as deined by Henry’s and Fick’s laws, respectively. Transport of gases and vapours in polymers is an important subject both from the technological and scientiic point of view. Applications include protective coatings, packing materials for food, pharmaceuticals and cosmetics and selective barriers for

195

Engineering Plastics gas or liquid mixtures. In the case of food packages, polymeric materials should exhibit an adequate CO2/O2 ratio (generally lower than 7) [35]. The process of permeation involves the dissolution of the gas on one side of the membrane, diffusion of the gas through it and release of other gas from the other side of the membrane. When dealing with glassy polymers, it is important to note that permeability characteristics depend on the thermal history of the polymer [36]. A conventional method for determining permeability and diffusion coeficients in polymers involves the measurement of membrane weight gain versus time until the inal mass of equilibrium mass is reached. There is a continuing need for improved barrier properties and extended shelf life in packaging for food and beverages, cosmetics, and pharmaceuticals. Additives that help create a protective package environment, polymers with good barrier properties, processes for creating modiied atmosphere packaging and sensors to measure the package environment can all be combined. It is expected that within the next decade, active and intelligent packaging options will become key elements in how food processors and manufacturing protect the longevity and nutrient value of their products. Active packaging responds to changes in the package environment. For example, when the relative humidity in a package reaches a certain level, a desiccant in the package will begin to absorb moisture. Active packaging systems may absorb molecules such as oxygen, ethylene, or moisture, or release agents such as antimicrobials or lavours. While many packaging technologies such as desiccants, odour scavengers and ethylene absorbers are commonly used in sachets that are inserted into a package, there is a drive to ind ways to incorporate active packaging technologies directly into the package walls. Georgiev and co-workers [37] showed that PTFE and luorinated ethylene propylene are resistant to most chemical solvents, heat sealable, and have low moisture uptake, which make them attractive as packaging materials for electronics and implantable devices. Polymer micro-joints were fabricated by using focused infrared laser irradiation. Laser bonded samples were tested with a micro-testing machine under lap shear load and the bond strength was determined. The bond strength of polymertitanium bonds was found to be in the range of 3.32 and 8.48 N/mm2, respectively. The failure mode of the mechanically tested samples was studied by using optical microscopy and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Chemical interactions during laser bonding of luorinated ethylene propylene to titanium were studied by using X-ray photoelectron spectroscopy, which gave evidence for the formation of Ti-F bonds in the interfacial region. Photoacoustic spectroscopy and related photothermal procedures [2] are well established spectroscopic techniques. The photoacoustic technique, apart from providing direct optical absorption spectra, can also be used to perform depth

196

Other Engineering Applications proile analysis, and characterisation of thermal properties. In addition, there has been a substantial development of new versatile and competitive instrumentation and experimental methodologies suitable for use in daily practice [38, 39]. Further details on the photothermal wave phenomenon and its applications can be found in the books by Rosencwaig [38] and Almond and Patel [39] and in some of many reviews published on the subject [40-42]. The room temperature characterisation of an LDPE sample’s thermal properties was based upon the measurements of the thermal diffusivity, α, and of the heat capacity, ρcp, where ρ is the material density and cp is the speciic heat at constant pressure (heat capacity per unit volume) [43]. To complete the determination of the sample thermal properties, knowing α and ρcp the sample thermal conductivity, K, is readily obtained from Equation 8.1:

K = α ρcp

(8.1)

The thermal diffusivity can be accurately measured by the photoacoustic technique. This technique looks directly at the heat generated in a sample, due to a thermal relaxation process, following the absorption of light. Among several experimental set-ups the open photoacoustic cell method has been used [43]. It consists of mounting the samples directly onto a cylindrical electric microphone and using the front air chamber of the microphone itself as the usual gas chamber of a conventional photoacoustic cell. As a result of the periodic heating of the sample following the absorption of modulated light, the pressure in the microphone chamber oscillates at the chopping frequency yielding the photoacoustic signal. The experimental arrangements (Figure 8.1) consisted of a 100 mW argon laser whose beam was modulated with a mechanical chopper. The sample was placed directly above the opening of the microphone covering it. The signal from the microphone was connected to a lock-in ampliier used to register both signal amplitude and phase. The contribution to the photoacoustic signal from the thermoelastic bending is the dominant mechanism. This effect is essentially due to the temperature gradient created inside the sample along an axis perpendicular to the surface exposed to the incident radiation [43]. Permeation studies of CO2 and O2 were performed using a sample holder which had its sides sealed off one from another. The permeate gas being studied was introduced on one side and kept at a constant pressure of 0.10 MPa. On the other side the concentration of the gas was measured using a photoacoustic gas analyser as it was

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Engineering Plastics being stored (Figure 8.2). The gas concentration rise (C), in these conditions, is given by [43]:

C = C0(1–e–1/τ )

(8.2)

D

Where: C0: Gas concentration at saturation; τD: ls2/2/D is the gas diffusion time; D: Gas diffusion coeficient; and ls: Sample thickness (40 µm).

Lens

Chopper Microphone

Light

Sample

(a) Lock-in amplifier

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Vacuum

Nylon

Glass-window Termocouple Light

(b)

Sample

Figure 8.1 Experimental arrangement for photoacoustic thermal diffusivity (a) and speciic heat capacity (b) measurements. Reproduced with permission from L.H. Poley, A.P.L. Siqueira, M.G. de Silva, H. Vargas and R. Sanchez, Polimeros: Ciência e Tecnologia, 2004, 14, 1, 8. ©2004, Associação Brasileira de Polímeros [43]

Manometer

Sample

URAS

Nedle Value

Computer

Gases

Figure 8.2 Experimental arrangement used for gas diffusion studies. URAS: photoacoustic gas analyser (URAS 14 from Hartman and Braun). Reproduced with permission from L.H. Poly, A.P.L. Siqueira, M.G. de Silva, H. Vargas and R. Sanchez, Polimeros: Ciência e Tecnologia, 2004, 14, 1, 8. ©2004, Associação Brasileira de Polímeros [43]

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Engineering Plastics Thus, by monitoring the time evolution of the gas concentration, the gas diffusion time, τ, and the diffusion coeficient, D, can be determined. All measurements were performed at 27 °C. Figure 8.3 shows a typical photoacoustic signal frequency dependence for LDPE. It can be seen that for the modulation frequencies higher than 100 Hz, the signal amplitude scales essentially as f –0.94close to the theoretical value of f –1. This frequency dependence of the photoacoustic signal of a thermally thick sample conirms that thermoplastic bending is the dominant mechanism responsible for the acoustic signal [43].

Signal (mV)

0,1

0,01

f –0.94

100

Frequency (Hz)

Figure 8.3 Modulation Frequency Dependence of Photoacoustic Signal for LDPE. Reproduced with permission from L.H. Poley, A.P.L. Siqueira, M.G. da Silva, H. Vargas and R. Sanchez, Polimeros: Ciência e Tecnologia, 2004, 14, 1, 8. ©2004, Associação Brasileira de Polímeros [43]

Concentrations of CO2 and O2in the analyser chamber as a function of time are presented in Figure 8.4. The itting of experimental data to Equation 8.2 allows the determination of diffusion coeficients. The values obtained for diffusion coeficients of LDPE to O2 and CO2were 1.68 × 10–7 cm2/s and 2.77 × 10–8 cm2/s, respectively.

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Other Engineering Applications These values agree with those presented in literature for LDPE [45] (6.9 × 10–8 cm2/s for carbon dioxide and 4.6 × 10–7 cm2/s for oxygen).

(a)

Concentration CO2 (% in vol.)

20

16

12

8 (b) 4

0 0

5

10

15 20 Time (h)

25

30

35

Figure 8.4 Oxygen (a) and carbon dioxide (b) concentration evolution for LPDE. The solid line represents the best it of the experimental data to Equation 8.2 using τD as an adjustable parameter. Reproduced with permission from L.H. Poly, A.P.L. Siqueira, M.G. de Silva, H. Vargas and R. Sanchez, Polimeros: Ciência e Tecnologia, 2004, 14, 1, 8. ©2004, Associação Brasileira de Polímeros [43]

High barrier polymers are of increasing interest and used nowadays in food packaging applications. The reason for this is that packaging is more often regarded as a very eficient and convenient means of preserving foodstuffs from deterioration during product handling and transport. Recently, photothermal techniques have been applied to the determination of diffusion coeficients in biopolymers [45]. However, the complete validation of this new methodology requires a knowledge of the characterisation of diffusion coeficients of plastic ilms used commercially, which has been achieved successfully using traditional gravimetric techniques.

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Engineering Plastics This work involved the use of photothermal techniques for determining the diffusion coeficients of O2 and CO2 of commercial LDPE. The methodology involved the monitoring of diffused gas by a photoacoustic analyser. Diffusion coeficients measured for CO2 and O2 were 2.77 × 10–8 cm2/s and 16.8 × 10–8 cm2/s, respectively. To support the gas diffusion results, thermal properties were studied using photoacoustic spectroscopy and crystallinity was determined using X-ray diffraction. Values obtained for the thermal diffusivity and speciic heat capacity were 0.00165 cm2 and 2.33 J/cm3/K, respectively, which were in good agreement with the values found in the literature for pure LDPE and thus, assured the reliability of the diffusion coeficient values. Vibrational spectroscopy is one of the most widely used techniques for the morphological characterisation of high gas and aroma barrier materials used in food packaging. However, because of the highly hydrophobic character of ethylene-vinyl alcohol (EVOH) resins, it is usually LDPE, a high water barrier material that is put in direct contact with the packaged commodity, i.e., multi-layer EVOH-LDPE ilm [46]. The excellent properties of EVOH resins in terms of high gas, hydrocarbon and aroma barrier and transparency have allowed them to become widely implemented in many commercial applications where high barrier properties are needed to minimise product losses due to deterioration. Despite the excellent performance of these materials in high barrier food packaging applications, the materials are easily plasticised by moisture and, consequently, in most packaging applications are commonly encapsulated in multi-layer structures between hydrophobic polymers such as PP or PE. Various workers have studied the application of Fourier-Transform infrared spectroscopy (FT-IR) to determine diffusion coeficients of mostly water vapour, in various polymers [47-50]. In particular, the work of Lagarón and co-workers [46] is discussed next. Lagarón and co-workers [46] used vibrational spectroscopy to characterise the morphology and barrier properties of polymers used in food packaging. Raman and infrared spectroscopies were used for the morphological characterisation of EVOH copolymers (Soarnol, Nippon Chemical Industry, Japan), one of the families of high gas and aroma barrier materials most widely used in commercial food packaging. The effects of thermal history, annealing and thermal degradation of the copolymers on their crystallinity, morphological and chemical structure were examined. FT-IR spectroscopy was used to determine the diffusion coeficients of citrus fruit aroma components in LDPE. Figure 8.5 shows typical subtraction FT-IR spectra of a chosen band characteristic of the citrus fruit aroma limonene as a function of time during desorption from LDPE.

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1

0.8

0.6

0.4

0.2

0 900

895

880

885 980 Wavenumbers

875

870

Figure 8.5 Subtraction spectra from a completely desorbed LDPE sample of CH deformation mode of limonene as a function of time. Reproduced with permission from J.M. Lagarón, D. Cava, E. Giménez, P. Hernandez-Muñoz, R. Catala and R. Gavara, Macromolecular Symposia, 2004, 205, 225. ©2004, Wiley [46]

By itting the relative area of the chosen Raman absorption bands as a function of time to the modiied solution from Fick’s second law for a desorption case in an FTIR experiment it is easy to derive the corresponding diffusion coeficient:

3 - D ^2n + 1 h2 r2 t Ax 1 1 = 82 / 2 exp ' Ae L2 r n = 0 ^2n + 1 h

(8.3)

In Equation 8.3 (only strictly valid if Fickian behaviour is assumed), no changes in ilm thickness (n) and constant absorption coeficient, Aτ is the absorbance of the

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Engineering Plastics chosen band at a given time, t, and Ae is the absorbance at saturation or equilibrium sorption, L is the thickness of the ilm and D the diffusion coeficient. Lagarón and co-workers [46] carried out measurements for a number of aroma components, namely, limonene, α-pinene and citral, and results are given in Table 8.3.

Table 8.3 Diffusion coefficients (D) (m2/s) of limonine, α-pinene and citral through LDPE Aroma consistent D gravimetry D (FT-IR) Limonene (20.0 ± 0.3) × 10–13 (18.5 ± 0.6) × 10–13 α-Pinene (9.7 ± 0.2) × 10–13 (9.6 ± 0.6) × 10–13 –13 Citral (3.5 ± 0.2) × 10 (5.5 ± 0.1) × 10–13 Reproduced with permission from J.M. Lagarón, D. Cava, E. Giménez, P. Hernandez-Muñoz, R. Catala and R. Gavara, Macromolecular Symposia, 2004, 205, 225. ©2004, John Wiley and Sons [47]

To compare the results obtained for the determination of diffusion coeficients by FT-IR they also measured desorption of these penetrants by gravimetry, i.e., by using weight loss measurements. Figure 8.6 shows the corresponding its of the desorption experiments of α-pinene by FT-IR and gravimetry and these results showing an excellent correspondence. In the case of limonene and citral small differences between FT-IR and gravimetric results occur. The general criteria for selecting a good IR band to evaluate transport properties is that it should not undergo signiicant changes in shape and position during desorption, because this is indicative of vibrational modes highly sensitive to the different levels of interactions that can be established, depending on the sorption level between the penetrant and the polymer matrix. The reason why strong frequency shifts and changes in band shape, (often the case for N-H or O-H stretching bands and CO stretching bands) may not give good correlations with for example gravimetry, lies in the fact that absorption coeficients are changing during the desorption process, and therefore, the relationship between absorption and concentration may be signiicantly different during the experiments. Auras and co-workers [51] studied the variations in the oxygen diffusion, solubility, and permeability coeficients of polylactide ilms at different temperatures (5, 23 or 40 °C) and water activities (0-0.9). A modiied Ox-Tran 100-Twin with a coulometric sensor (Mocon, Inc., Minneapolis, MN, USA) was used for measuring the permeability of oxygen through the polymer ilms as a function of the water activity (Aw) which is

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Other Engineering Applications the ratio of the partial pressure of water to the saturation vapour pressure of water at a speciied temperature).

1.0 0.9 0.8

Mt /Mo ; At /Ao

0.7 0.6 0.5

Gravimetry FT-IR

0.4 0.3 0.2 0.1 0.0 0

1000

2000

3000

4000

5000

6000

7000

Time (s)

Figure 8.6 Fickian-like desorption experiments of α-pinene in LDPE by FT-IR and gravimetry. Reproduced with permission from J.M. Lagarón, D. Cava, E. Giménez, P. Hernandez-Muñoz, R. Catala and R. Gavara, Macromolecular Symposia, 2004, 205, 225. ©2004, Wiley [46]

The results were compared with the oxygen diffusion, solubility, and permeability coeficients obtained for PET ilms under the same conditions. The water sorption isotherm for polylactide ilms was also determined. Diffusion coeficients were determined with the half-sorption time method. Also, a consistency test for continuouslow permeability experimental data was run to obtain the diffusion coeficient with the lowest experimental error and to conirm that oxygen underwent Fickian diffusion in the polylactide ilms. The permeability coeficients were obtained from steady-state permeability experiments. The results indicated that the polylactide ilms absorbed very low amounts of water, and no signiicant variation of the absorbed water with the

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Engineering Plastics temperature was found. The oxygen permeability coeficients obtained for polylactide ilms (2−12 × 10–18 kg.m/m2.s.Pa) were higher than those obtained for PET ilms (1−6 × 10–19 kg.m/m2.s.Pa) at different temperatures and water activities. Moreover, the permeability coeficients for polylactide and PET ilms did not change signiicantly with changes in the water activity at temperatures lower than 23 °C. Markarian [52] reviewed the latest additives used to improve gas barrier and other properties of food packaging, cosmetics and pharmaceutical products. These include oxygen and scavengers, lavour and odour controllers, antimicrobials, antifogs and UV absorbers. Barrier packaging oxygen scavengers discussed in this review include ascorbic acid, iron oxide (in sachets), cobalt catalysed Nylon MXD6 (Mitsubishi), Shelfplus O2 (Ciba) oxygen scavenger, C6OSP oxygen scavenger (based on an oxidisable resin (Chevron Phillips Chemical)), ethylene methyl acrylate cyclohexanemethylacrylate containing a photoiniator and a cobalt salt catalyst and BP Chemical Amosorb™ oxygen scavenger. Mazzocca [53] studied the interactions between packaged commodities, polymers and environments (vapours, micro- and macro-organisms and radiation) leading to the migration of additives from plastic packaging ilms into packaged commodities and diffusion of materials through the ilms. Toxicological implications of migration were considered. The gas and water vapour permeability, chemical resistance and resistance to biological attack of plastics commonly used in packaging applications are also discussed.

8.6 Foam Insulation Various researchers have discussed properties such as insulation and ozone depletion in refrigerator foam systems [54-64]. The refrigerator industry has now replaced the chloroluorohydrocarbon 141 blowing agent for the production of rigid PU foam insulation with the hydroluorocarbon (HFC), 1,1,1,3,3-pentaluoropropane (HFC 245fa),which has zero ozone depletion potential. The conversion to the HFC 245fa blowing agent has resulted in higher formulation costs because of the increased price of the blowing agent. The higher cost has created an opportunity for the development of innovative products aimed at reducing the concentration of the blowing agent and thereby improving overall foam economics. Critical foam physical properties in the appliance segment include: low density, dimensional stability, thermal conductivity (k-factor), compression strength, percentage of closed cells and wettability as the foam rises up the mould walls. The ideal product will allow for improved low and dimensional stability through optimised cell structure and/or a

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Other Engineering Applications more uniform density distribution, with no negative impact on thermal properties. Subsequently, this will allow for either lower concentrations of the blowing agent or reduction of the over-packed density. These changes would contribute to improvements in processing parameters and lower raw material usage, thereby reducing the appliance manufacturer’s inal costs.

8.7 Radiation Resistance of Engineering Plastics

8.7.1 Gamma Radiation In some applications, particularly in the nuclear industry, medical instrumentation and food sterilisation, plastics are subjected to damage, which is associated with a loss in molecular weight and deterioration of some physical properties, such as impact strength and colour change upon exposed the plastics to gamma rays [65, 66]. It can be seen in Table 8.4 that several polymers such as polystyrene (PS), polyether ether ketone (PEEK) and polyether-imide (PEI) enjoy an excellent resistance to gamma rays, whilst a wide range of polymers have very good resistance to gamma rays. Thus, reinforced polyimide (PI) upon exposure to gamma rays had a decay of short term shear strength for a zero dose value of 87.1 to 79.3 MPa after cobalt 60 irradiation to 1,000 kGy

207

Engineering Plastics

Table 8.4 Resistance of plastics to gamma rays Excellent •  PS •  PEEK •  PEI

Very good •  XPE •  LDPE •  Polyisobutylene •  Styrene-butadiene •  High-impact polystyrene •  Epoxies •  Polybutylene terphthalate •  PET •  Diallyl isophthalate •  Diallyl phthalate •  Alkyd ethylene tetraluoroethylene •  PC •  Phenol-formaldehyde •  Styrene-maleic anhydride •  PA 6, PA 6,6, PA 6,9, PA 6,10 and PA 6,12  •  PAI •  PI  •  PU  •  Styrene-acrylonitrile EVA: Ethylene-vinyl acetate LDPE: Low-density polyethylene PA: Polyamide PAI: Polyamide imide PC: Polycarbonate PET: Polyethylene terephthalate PMMA: Polymethyl methacrylate PP: Polypropylene PTFE: Polytetraluoroethylene PU: Polyurethane XPE: Crosslinked polyethylene Source: Author’s own iles

Poor •  LDPE •  PP •  PMMA •  EVA •  Urea-formaldehyde •  PTFE •  Perluoroalkoxyethylene •  Ethylene-propylene

8.7.2 Ultraviolet Radiation Several polymers have an excellent resistance to ultraviolet (UV) radiation which renders them candidates for applications such as outdoor exposure and exposure to artiicial lighting. These include PEEK, PEI, diallyl isophthalate, and EVA, see Table 8.5.

208

Other Engineering Applications

Table 8.5 UV radiation resistant polymers Excellent •  PEEK •  Diallyl isophthalate •  EVA •  PEI •  Polyvinyl luoride •  Polyvinylidene luoride •  Perluoroalkoxyethylene •   Ethylenechlorotriluoroethylene •   Fluorinated ethylenepropylene •  Silicones

Very good •  Crosslinked polyethylene •  Polyisobutylene •  Styrene-ethylene-styrene  •  Polystyrene •  Epoxies •  PET •  Diallyl phthalate •   Ethylenetetraluoroethylene •  PC •  Phenol-formaldehyde •   PA 6, PA 6,6, PA 6,9, PA  6,10, PA 10 and PA 12 •  PTFE •  Chlorinated PVC •  Unplasticised PVC •  Polyphenylene sulide •  PSU

Poor •   High-density  polyethylene •  LDPE •  PP •  Polyisobutylene •  Polymethylpentene •  Pentene •  Ethylene-propylene •  Styrene-maleic anhydride •  PAI •  PI •  PMMA •  Urea-formaldehyde •  Styrene acrylonitrile •   Acrylonitrile-butadienestyrene •  Polyether sulfone

PSU: Polysulfone PVC: Polyvinyl chloride Source: Author’s own iles

Several polymers combine excellent ultraviolet resistance with good tensile and elongation at break properties as illustrated in Table 8.6.

Table 8.6 Selection of plastic with excellent UV resistance and tensile and elongation properties Polymer PEEK PET EVA XPE Perluoroalkoxyethylene PC Ethylene-trichloroluoroethylene Fluorinated ethylene-PP Source: Author’s own iles

Elongation of break (%) 400 300 750 350 300 200 200 150

Tensile strength (MPa) 92 55 17 18 29 50 30 14

UV resistance Excellent Excellent Excellent Excellent Excellent Excellent Excellent Excellent

209

Engineering Plastics

8.7.3 Electron Irradiation Storage modulus, alpha relaxation and creep behaviour in polymers are inluenced by electron irradiation. Thus, creep strain increased upon exposure to electron beam irradiation, below 4 MRad.

8.7.4 Neutron/Gamma Irradiation Neutron gamma irradiation has an adverse effect on some polymer properties. Thus, some glass ibre reinforced plastics lose about 2−40% of their lexural strength after exposure to neutron/gamma irradiation doses above 1 × 10–1 Gy [67]

References 1.

FAPU, 2002, 13, July-August, 5.

2.

M. Bogdan, J. Hoerter and F.O. Moore in Proceedings of the Alliance for the Polyurethanes Industry - Polyurethanes Expo 2003, Orlando, FL, USA, 2003, p.47.

3.

K. Dedecker, M. Baes and S.N. Singh in Proceedings of the UTECH Europe Conference, The Hague, Holland, 2003, Paper No.36.

4.

EN13165, Thermal Insulation Products for Buildings – Factory Made Rigid Polyurethane Foam (PU) Products - Speciication (Annex C), 2012.

5.

S.N. Singh, M. Ntiru and K. Dedecker, Rubber and Plastics News, 2003, 32, 18, 15.

6.

CAN/ULC-S770-00, Standard Test Method for Determination of Long-Term Thermal Resistance of Closed-Cell Thermal Insulating Foams, 2000.

7.

C. Chittolini, R. Dellavalle and A. Stefani, Macplas International, 2003, April, 106.

8.

Plastics in Building Construction, 1997, 21, 10, 2.

9.

UL 790, Standard for Standard Test Methods for Fire Tests of Roof Coverings, 2004.

10. D. Barpanda and P.R. Mantena, Journal of Reinforced Plastics and Composites, 1998, 17, 3, 234. 210

Other Engineering Applications 11. M. Xanthos, S.K. Dey, S. Mitra, U. Yilmazer and C. Feng, Polymer Composites, 2002, 23, 2, 153. 12. C.T. Love and V.M. Karbhari in Proceedings of the SAMPE 06 Conference – Creating New Opportunities for the World Economy, Long Beach, CA, USA, 2006, Paper No.235. 13. K.R. Kistler and E.L. Cussler, Chemical Engineering Research and Design, 2002, 80, 1, 53. 14. S. Veiseh and A.A. Yousei, Iranian Polymer Journal, 2003, 12, 4, 323. 15. H-P. Brack, D. Ruegg, H. Bührer, M. Slaski, S. Alkan and G.G. Scherer, Journal of Polymer Science Part B: Polymer Physics Edition, 2004, 42, 13, 2612. 16. R. Dweiri and J. Sahari, Journal of Power Sources, 2007, 171, 2, 424. 17. S.A. Gürsel, J. Schneider, H.B. Youcef, A. Wokaun and G.G. Scherer, Journal of Applied Polymer Science, 2008, 108, 6, 3577. 18. Macplas International, 2003, April, 116. 19. C.M. Topping, J. Jin, S.C. Ligon, A.V. Patil, D.W. Smith, S. Fallis, J.A. Irvin and D.D. Des Marteau and in Proceedings of the ACS Spring Meeting, Orlando, FL, USA, 2002, p.486. 20. Z. Chen, L. Christensen and J.R. Dahn, Journal of Applied Polymer Science, 2004, 91, 5, 2949. 21. J.C. Arrebola, A. Caballero, M. Cruz, L. Hernán, J. Morales and E.R. Castellón, Advanced Functional Materials, 2006, 16, 14, 1904. 22. S.H. Joo, C. Pak, E.A. Kim, Y.H. Lee, H. Chang, D. Seung, Y.S. Choi, J-B. Park and T.K. Kim, Journal of Power Sources, 2008, 180, 1, 63. 23. D. Tasis, A. Tagmatarchis, A. Bianco and M. Prato, Chemical Reviews, 2006, 106, 3, 1105. 24. Composites International, 2002, 52, July-August, 64. 25. H. Miller, Medical Device and Diagnostic Industry, 2004, 26, 5, 98. 26. M.T.K. Ling, C. Sandford, A. Sadik, H. Blom and S.Y. Ding, Plastics Engineering, 2001, 57, 1, 50. 211

Engineering Plastics 27. C. Frissora, Medical Device and Diagnostic Industry, 2007, 29, 5, 80. 28. D.W. Hahn, D.L. Wolfarth and N.L. Parks, Journal of Biomedical Materials Research, 1997, 35, 1, 31. 29. Plastics News International, 2003, June, 21. 30. R. Pell, Medical Device and Diagnostic Industry, 2006, 28, 10, 100. 31. S. Green and K. Cartwright in Proceedings of the Rapra Technology Conference of Medical Polymers, Dublin, Eire, 2003, Paper No.5. 32. S. Green, Medical Device and Diagnostic Industry, 2005, 27, 5, 104. 33. M. Jarman-Smith, Medical Device Technology, 2008, 19, 6, 12. 34. C. Wolf, K. Lederer and U. Muller, Journal of Materials Science: Materials in Medicine, 2002, 13, 7, 701. 35. S. Marais, J.M. Saiter, C. Devallencourt, Q.T. Nguyen and M. Métayer, Polymer Testing, 2002, 21, 4, 425. 36. V. Campañ, A. Ribes, R. Díaz-Calleja and E. Rianda, Polymer, 1996, 37, 11, 2243. 37. G.L. Georgiev, T. Sultana, R.J. Baird, G. Auner, G. Newaz, R. Patwa and H. Herfurth, Journal of Materials Science, 2009, 44, 3, 882. 38. A. Rosencwaig in Photoacoustic and Photothermal Spectroscopy, 2nd Edition, R.E. Kreiger Publishing Company, Malabar, FL, USA, 1990. 39. D.P. Almond and P. Patel in Photoacoustic and Photothermal Sciences and Techniques, Chapman and Hall, London, UK, 1996. 40. H. Vargas and L.C.M. Miranda, Physics Reports, 1988, 161, 2, 43. 41. J.B. Kinney and R.H. Staley, Annual Review of Materials Science, 1982, 12, 295. 42. A. Torres Filho, N.F. Leite, L.C.M. Miranda, N. Cella and H. Vargas, Journal of Applied Physics, 1989, 66, 1, 97. 43. L.H. Poley, A.P.L. Siqueira, M.G. da Silva, H. Vargas and R. Sanchez, Polimeros: Ciência e Tecnologia, 2004, 14, 1, 8.

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Other Engineering Applications 44. Polymer Handbook, 3rd Edition, Eds., J. Brandrup and E.H. Immergut, John Wiley and Sons, New York, NY, USA, 1989. 45. M.G. da Silva, S.S. Gonçales, M.S. Sthel, D.U. Schramm, R.R. Sanchez, J.B. Rieumont and H. Vargas, Review of Scientiic Instruments, 2003,74, 1, 831. 46. J.M. Lagarón, D. Cava, E. Giménez, P. Hernandez-Muñoz, R. Catala and R. Gavara, Macromolecular Symposia, 2004, 205, 225. 47. G.T. Fieldson and T.A. Barbari, Polymer, 1993, 34, 6, 1146. 48. C. Sammon, N. Everall and J. Yarwood, Macromolecular Symposia, 1997, 119, 189. 49. C.M. Balik and W.H. Simendinger, III, Polymer, 1998, 39, 20,4723. 50. S. Cotugno, G. Larobina, G. Mensitieri, P. Musto and G. Ragosta, Polymer, 2001, 42,15, 6431. 51. R. Auras, B. Harte and S. Selke, Journal of Applied Polymer Science, 2004, 92, 3, 1790. 52. J. Markarian, Plastics, Additives and Compounding, 2004, 6, 4, 22. 53. I. Mazzocca, Materie Plastiche ed Elastomeri, 1982, 12, December, 716. 54. J. Feighan and K. Dedeker in Proceedings of the Alliance for the Polyurethane Industry Conference, Orlando, FL, USA, 2003, p.487. 55. J.W. Miller, R.F. Hoffman and P.C. Hohl in Proceedings of the Alliance for the Polyurethane Industry - Polyurethane Conference, Salt Lake City, UT, USA, 2002, Technical Session L-Appliance, Paper No.2, p.465. 56. D. Williams in Proceedings of the Alliance for the Polyurethane Industry Polyurethane Conference, Salt Lake City, UT, USA, 2002, Technical Session D-Blowing Agents, Paper No.1, p.135. 57. J. Feighan, J. Deschaght and F. Magnani in Proceedings of the Alliance for the Polyurethane Industry - Polyurethane Conference, Salt Lake City, UT, USA, 2002, Technical Session L-Appliances, p.475. 58. R.W. Johnson in Proceedings of the Alliance for the Polyurethane Industry Conference, Orlando, FL, USA, 2003, p.513.

213

Engineering Plastics 59. J.W. Miller and R.F. Hoffman in Proceedings of the Alliance for the Polyurethane Industry Conference, Orlando, FL, USA, 2003, p.505. 60. E.E. Ball and K.J. Elsken in Proceedings of the Alliance for the Polyurethane Industry Conference, Orlando, FL, USA, 2003, p.496. 61. H. Seifert, A. Biedermann and C. Giesker in Proceedings of the Alliance for the Polyurethane Industry Conference, Salt Lake City, UT, USA, 2002, Technical Session L - Appliance, Paper No.4, p.483. 62. M. Modesti, A. Lorenzetti, G. Gavasso and A. Bevilacqua in Proceedings of the Alliance for the Polyurethane Industry Conference, Orlando, FL, USA, 2003, p.660. 63. J. King, P. Irwin, I. Latham and S. Moore in Proceedings of the Alliance for the Polyurethane Industry Conference, Salt Lake City, UT, USA, 2002, Technical Session L – Appliance, Paper No.1, p.455. 64. L. Zipfel, Urethanes Technology, 2002, 19, 1, 21. 65. C.L. Homrighausen, A.S. Mereness, E.J. Schutte, B. Williams, N.E. Young and R. Blackburn, High Performance Polymers, 2007, 19, 4, 382. 66. A.L. Babovich, Y. Unigovski, E.M. Gutman and E. Kolmakav in Proceedings of the 63rd SPE ANTEC Conference, Boston, MA, USA, SPE, Brookield, CT, USA, 1-5th May, 2005, Paper No.5. 67. S. Spiessbergen, K. Humer, E.K. Tschegg, H.W. Weber and H. Gerstenberg, Advances in Cryogenic Engineering, 1996, 42, 105.

214

A

ppendix 1

Applications of engineering polymers Polymer Low-density polyethylene

Mechanical Piping

High-density polyethylene

High rigidity applications, piping Bearings, gears, artiicial joints

Ultra-high molecular weight polyethylene

Electrical Cables and wire insulation, sleeving -

Thermal -

Other Chemically resistant parts

-

-

-

-

Heat shrinkable tubing -

Can and bottling machine parts Rotational moulded tanks Medical components

Crosslinked polyethylene

Piping

-

PP

Impact resistance car bumper (rubber modiied), general mechanical parts, automatic applications Stiffness at elevated temperatures, automotive under the bonnet applications, air ducting channels Pipes, hoses Automotive under the bonnet applications

Electrical applications

PP, 20% talc illed

PP, UV stabilised PP, 20% glass ibre illed

PP, 20 and 40% calcium carbonate illed Ethylene-PP Car bumpers copolymers

Electrical systems housing

Housing for electric kettles

Cables -

Washing machine components

-

Cooling system expansion tanks -

-

-

Garden furniture -

215

Engineering Plastics Ethylene-PP elastomer

Power tool housings, car fascias Pipes

Ethylene-PP, ire retardant Ethylene-PP Low surface polyallomer hardness Alkyd resins short glass ibre reinforced

Alkyd resins, long glass ibre reinforced

-

-

-

Electrical components Wire coverings

-

-

-

Blow moulded boxes -

Automotive ignition, electronic switching, switches, relay base Electrical switching, insulation Switches, relay bases and capacitor encapsulation Switches, electrical ittings

-

Microwave ovens

-

-

-

-

Ducts, light itting housings, washing machine parts, dishwasher components Ventilator grills, cooling fans Chemical protection of pipes and structures, marine protection -

Alkyd resins, mineral and glass ibre reinforced

-

PPO

Automotive grill fascia panels

PPO, 10% glass ibre reinforced

Automotive instrument panels

-

Epoxy resins

-

Electrical components

Epoxy resins, silica illed Epoxy resins, mineral and glass ibre reinforced

-

Transformers

-

Encapsulation of electronic and electrical devices, protection of capacitors, resistors and so on

216

Components for heating systems -

-

-

Appendix 1 Epoxy resins, mineral illed Epoxy resins, glass ibre illed Epoxy resins, Kevlar prepreg

Epoxy resins, glass prepreg Epoxy resins, carbon ibre prepreg

PEEK

PEEK, 20% glass ibre reinforced

Power transmission equipment Power transmission equipment Chemical engineering plant construction, pressure vessels Building products, pressure vessels Structural components, boat hulls, chemical engineering plant, pressure vessels Engineering products

Automotive applications

Switch gear insulation

-

-

Switch gear insulation

-

-

-

-

Aerospace applications

-

-

-

-

Aerospace applications Aerospace applications, helicopter blades

Wire covering

-

Electrical components, printed circuit boards PEEK, 30 or 10% glass Automobile Electrical ibre reinforced engineering, components, bearing tubes, cam printed circuit rings boards PEEK, 35% mica and High dimensional Electrical glass ibre reinforced stability components components, structural housings PEEK, 30% carbon Automotive ibre reinforced cams engines, pump impellers, bearings, bushes POM (polyacetals) Gears, bearings, photopolymer fan blades, load bearing mechanical parts, parts requiring good abrasion resistance

High temperature applications

Aerospace applications where gamma radiation resistance is required Aerospace applications

-

Missile and aircraft nose cones

-

-

-

Structural aerospace applications

-

-

217

Engineering Plastics POM, glass ibre Pump housings, reinforced or UV pipe ittings stabilised POM, PTFE lubricated Bearings, gears, fan blades POM, 30% glass ibre Gears, bearings, reinforced bushes POM, 30% carbon Bearings, cams, ibre reinforced gears POM, 2% silicone Gears, bearings, lubricated bushes Diallyl isophthalate -

Diallyl isophthalate, long glass ibre reinforced Diallyl isophthalate, mineral illed

Pump impellers

-

Diallyl isophthalate, short glass ibre reinforced

-

PC

Engineering plastics, safety shields, glazing panels

PC, ire retardant

Engineering plastics, safety shields, glazing panels Replacement for metal parts -

PC, 20% glass ibre reinforced PC, 30% glass ibre reinforced PC, high low

218

-

-

-

Sporting equipment

Switch components -

-

-

-

-

-

Sporting equipment -

-

-

Electrical connectors, switch gear housings Switchgear, brush holders

-

Snap-it components -

-

-

-

-

-

Electrical connections, relays, switches, communicators Connectors, relays, switching gear, brush holders Electrical switchgears

Electrical appliances

-

Bullet proof glazing, applications which require chemical resistance -

Electrical enclosures Electrical enclosures, relay separators -

-

-

-

-

-

Applications which require clarity

Appendix 1 PC, 30% carbon ibre reinforced Polyester resin moulding compound

PMMA (general purpose)

High strength plastic Pipe joints, guards, metal replacement, high strength applications Building and engineering applications Automotive components

PMMA (high-impact)

-

Polyester, sheet moulding compounds

PET, 45 and 55% glass Gears, sprockets, ibre reinforced propellers, automotive bumpers PET, 45% mineral and Automotive glass ibre reinforced, ignition ire retardant PET High tolerance automotive and other mouldings PET, crystalline Industrial plugs and sockets

PET, ire retardant PET, 30% glass ibre reinforced, ire retardant

-

Housings for pumps, motors and so on, gears, sprockets PET, 36% glass ibre Extreme reinforced automotive body parts, casings and housings PET, 35% glass ibre Lawn mower reinforced, super tough and water pump housings, windscreen wiper arms

-

-

-

Good electrical performance

-

-

Electrical applications

-

-

-

-

-

-

-

-

Chemical plant applications, windscreens Glazing, automotive lamp housings -

Electrical components, terminal blocks Electrical ittings and components

-

Transformer bobbins, housings for electrical apparatus Electrical components Electrical components

-

-

-

-

-

-

Electrical components

-

-

-

-

Furniture components

-

219

Engineering Plastics PMMA, cast sheet

Machinery guards

-

PBT

PBT, ire retardant

Under body components of cars -

-

-

PBT, 10-20% glass ibre reinforced

Automotive distributor caps

-

Telecommunications components

PBT, 30% glass ibre reinforced, ire retardant PBT, 30% glass, head illed PBT, 45% mineral and glass ibre illed

Engineering parts

Electrical connectors, switches Switches, motor components Lamp sockets, switches, motor housings, lamp sockets Electrical motor parts, switches

-

-

Engineering parts

-

-

-

-

-

-

Bearings, gears

-

Heating appliances, oven grills -

Ultra-high strength and stiffness applications Cams, gears, bushings, fuel tanks, door closures Bearings, cams Automotive parts

-

-

-

Electrical connectors

-

-

Electrical parts

-

-

-

-

-

Terminal clocks, transformers

-

-

-

-

-

-

-

-

Electrical components

-

-

PBT, 2% silicone lubricated PBT, 30% carbon ibre illed PA 6

PA 6, MoS2 PA 6, 30% glass ibre reinforced PA 6, 30% carbon ibre Bearings, highreinforced strength structures PA 6,6 and 6,9 Mechanical components, timing chains, gears, cams, bolts PA 6,6, super tough Automotive applications PA 6,6, 4% mineral Under bonnet reinforced mechanical parts PA 6,6, high-impact Automotive parts

220

-

Solar panels, glazing, lamp housings Heat resistant Light ittings panels

-

Appendix 1 PA 6,6, 60% glass ibre High strength reinforced and stiffness applications PA 6,6, MoS2 Bearings, valves, seals, cams gears PA 6,6, carbon ibre Connecting rods reinforced PA 6,10, 10-30% glass Precision ibre reinforced engineering, gears, cams, bearings, valve seals PA 6,10, carbon ibre Precision reinforced engineering parts PA 11 Hose for automotive use, gears, cams PA 11, 30% glass ibre reinforced PA 6,12

PA 6,12, 2% silicone lubricant PA 6,12, 20% PTFE lubricated PA 6,12, 10-30% glass ibre reinforced PA 12

PA 12, semi-lexible

PA 12, 30% glass ibre reinforced

-

-

-

-

-

-

-

-

-

Electrical connectors, plugs

-

Electrical components Electrical mechanical components, transformers Electrical plugs

-

-

-

-

Fan blades, gears, precision engineering parts Mechanical parts, abrasion resistance, low water absorption Gears, cogs, cams, bushes, valve seals Gears -

Heat resistant parts

Mechanical parts, low water absorption Injection moulded parts for automobiles, precision machining, fuel lines, air brakes Air ducts, petrol and oil pipes, automotive parts, cam cables, gears High precision stability applications, fan blades

-

-

-

-

-

-

-

-

-

Electrical and electronic application, cable and wire sleeving

-

-

-

-

-

Electrical plugs

Heat resistant housings

221

Engineering Plastics PA 12, 50% glass bead Parts with rigid illed dimensional stability, bushes, valves and so on Polyether-ester-amide Rubber based elastomer replacement in pipes, tubes and moulded parts PA-PPO alloy Automotive applications PA-ABS alloy Gears, impellers

Electrical coils and bobbins

-

-

-

-

-

-

-

-

Electro-technical components Electrical connectors Capacitor cable insulation, printed circuit boards, electrical communications Electric motor bearings

-

-

-

-

Very good thermal stability

-

Parts of aircraft engines, parts exposed to radiation -

-

-

-

-

-

-

Microwave parts, hightemperature switchgear Hightemperature connectors, heat exchangers Thermal protectors

-

ABS-PC alloy

Instrument panels

PI

Bearings, valve seals, piston rings, gears, bearing cases

PI, PTFE lubricated

Piston rings, machine tool bearings, pump bearings, valve discs Machine bearings, insulating bushes, drive rollers Valves seals, compressor rings Gear boxes Terminal boards

PI, MoS2 lubricated

PI, 25% graphite lubricated PI, 40% glass ibre reinforced PEI

Automotive under bonnet components

PEI, 10-20% glass ibre Cooling fans, reinforced gears, automotive under body components, fuel systems PEI, 30% glass ibre Explosion proof reinforced containers, automotive under bonnet components, heat exchangers, fuel systems

222

Electrical connectors

Electrical components, fuses

Electrical components, switches, controls, printed circuit boards

-

-

Appendix 1 PAI

PAI, glass ibre reinforced PAI, graphite illed

Polyurethane thermoplastic elastomer PPS, 30% carbon ibre illed

PPS, glass ibre and bead reinforced

PPS, 40% glass ibre reinforced

PPS, 20% PTFE lubricated PES

Valves, bearings, gears, parts for internal combustion engines Valve plates, pistons, gears, rotators Bearings, thrust washers, piston rings, seals, impellers Abrasion resistant rollers, bearings, gears, shock mountings Pump housings, valves, high strength structure components Automotive head lamps, under bonnet parts exposed to oil, petrol and hydraulic luids, pumps, valves, precision mechanical parts Automotive head lamps, petrol, oil and hydraulic luid resistant parts, exhaust gas emissions, control valves, pumps, precision mechanical parts Anti-friction gears, bolts and screws -

Electrical connectors, printed circuit boards

-

Parts for jet engines

Terminal strips, insulations

-

-

-

-

-

-

-

-

-

High heat applications

High chemical resistance applications

Boxes of electronic circuit relays, circuit breakers

High heat applications

High chemical resistance applications

Terminal blocks, High heat connectors, applications electric motor housings, boxes for electronic components

High chemical resistance applications

-

-

-

Electrical and electronic components

Medical parts requiring sterilisation

223

Engineering Plastics PES, 30% glass ibre reinforced

PSU

PSU, 30% glass ibre reinforced

PSU, 10% glass ibre reinforced

Under bonnet automotive applications, ittings and connectors in the gear box area, air ducting, car heating fans Engineering applications, valve bodies, under bonnet components, replacement for stainless steel parts Pumps, valves in the petrol chemical industry Automotive under bonnet applications

PSU, 30% carbon ibre Automotive reinforced under bonnet applications, chemical plant pumps, valves, process pipes, pump impellers PSU, 15% PTFE Pumps, valves lubricated

PTFE

224

Bearings, radiator lexible pipe and valve ittings, piston rings, diaphragms, gaskets, bearings

Electrical components, printed circuit boards

-

Nose cones

Electrical and electronic components, switch housings

Very good thermal stability

Medical sterilising trays, radiation resistance parts

Electrical components, printed circuit boards Electrical components, printed circuit boards, electronic ignition components Switch devices

-

-

-

Aerospace applications, alkaline battery cases

-

Aircraft interior and exterior components

-

Medical equipment requiring sterilisation

-

Chemical vessel linings

Electrical components, terminal blocks, housing for electronic components High temperature electrical insulation, electronic engineering applications

Appendix 1 PTFE, 60% bronze illed

High speed bearings, wear pads, piston rings PTFE, 15 or 25% glass Wear pads, piston ibre illed rings PTFE, 15% graphite Bearings, wear illed pads, piston rings EthyleneValve and pump chlorotriluoroethylene components

Ethylenechlorotriluoroethylene, glass ibre illed Ethylenetetraluoroethylene Ethylenechlorotriluoroethylene, 10 and 30% glass ibre illed Ethylenechlorotriluoroethylene, 30% carbon ibre illed Perluoroalkoxyethylene

Perluoroalkoxyethylene, 20% glass ibre reinforced PVDF

PVDF, 20% carbon ibre reinforced

-

-

-

-

-

-

Microwave parts -

Cable coverings

-

Valves

-

-

Components for pumps, valves Bearings in aggressive environments, pumps, impellers, valves, gears Bearings, seals, rings piston rings, valve plugs, compressor rings -

Wire coatings

-

-

-

-

-

-

-

-

-

-

-

Pipes, bearings

Wire insulation

Bearings, nuts, pump rotators, valve bodies

-

Heater cables Chemically resistant tank linings for pump pipes that operate at higher temperatures Heat Chemical shrinkable plant tubing Heat Chemical shrinkable plant tubing Use in aggressive environments

Anti-static applications Chemically resistant linings, optical iller tubing Chemical containers

225

Engineering Plastics Polyvinyl luoride

-

-

Polychlorotriluoroethylene

Chemically Packaging ilm resistant o-rings, for electronics, gasket seals, pump electronic parts sealants

-

-

Fluorinated-ethylene-PP Valve holding, non-stick valves

Terminal blocks, wire insulators, electronic components

Fluorinated-ethylene-PP, Valves 20% glass ibre coupled Silicones Abrasion resistant coatings

Electrical components Electronic components encapsulation Electronic components encapsulation

Silicones, glass ibre and mineral illed

-

ABS: Acrylonitrile-butadiene-styrene MoS2: Molybdenum disulide PA: Polamide(s) PAI: Polyamide-imide PBT: Polybutylene terephthalate PC: Polycarbonate PEEK: Polyether ether ketone PEI: Polyether-imide PES: Polyether sulfone PET: Polyethylene terephthalate PI: Polyimide PMMA: Polymethyl methacrylate POM: Polyoxymethylene PP: Polypropylene PPO: Polyphenylene oxide PPS: Polyphenylenesulide PSU: Polysulfone PTFE: Polytetraluoroethyene PVDF: Polyvinylidene luoride UV: Ultraviolet

226

-

-

Film covering of aircraft interiors to reduce lammability, solar panel glazing Cryogenic applications, aggressive chemical resistance Chemical lings, glazing ilm for solar panels, encapsulation Chemical plant Weather resistant coatings -

A

bbreviations

ABS

Acrylonitrile-butadiene-styrene

AC

Alternating current

AF

Acceleration factor

AFM

Atomic force microscopy

AISI

American Iron and Steel Institute

APL

Applied Physics Laboratory - John Hopkins University

ASTM

American Society for Testing and Materials

Aw

Water activity

BMC

Bulk moulding compound

Ca(OH)2

Calcium hydroxide

CAMPUS

Computer Aided Material Presentation by Uniform Standards

CNT

Carbon nanotubes

CO2

Carbon dioxide

DC

Direct current

DETA

Dielectric thermal analysis

DIN

Deutsches Institute für Normung

DMA

Dynamic mechanical analysis

DMFC

Direct methanol fuel cell

227

Engineering Plastics DMTA

Dynamic mechanical thermal analysis

DSC

Differential scanning calorimetry

DTA

Differential thermal analysis

ECP

Electrically conducting polymer(s)

ECTFE

Ethylene-chlorotrifluoroethylene

EMA

Ethylene methacrylate

EN

European Norms

EPDM

Ethylene-propylene-diene terpolymer

EPDM-g-TMEVS

Ethylene-propylene-diene monomer grafted with tris(2methoxyethoxy)vinylsilane

EPR

Ethylene-propylene rubber

EVA

Ethylene-vinyl acetate

EVOH

Ethylene-vinyl alcohol

FEP

Fluorinated ethylene-propylene

FIAT

Fabbrica Italiana Automobili Torino – automotive standards

FT-IR

Fourier-Transform infrared spectroscopy

GC

Gas chromatography

GFRP

Glass fibre-reinforced plastics

GP

General purpose

HDPE

High-density polyethylene(s)

HDT

Heat distortion temperature

HFC

Hydroflurocarbon(s)

IR

Infrared

228

Abbreviations ISO

International Organization for Standardization

KOH

Potassium hydroxide

LDPE

Low-density polyethylene(s)

LGF

Long glass fibre

LGF-PP

Long glass fibre - polypropylene

LLDPE

Linear low-density polyethylene

MDA

Methylene dianiline

MDPE

Medium-density polyethylene

MESSENGER

Mercury Surface, Space, Environment, Geochemistry and Ranging

MoS2

Molybdenum disulfide

MS

Mass spectrometry

MWCNT

Multi-walled carbon nanotube(s)

N/A

Material is brittle and does not exhibit a yield point

N/R

Not reported

N/Y

Material is ductile and does not exhibit a yield point

NaOH

Sodium hydroxide

NASA

National Aeronautics and Space Administration (The)

NBR

Nitrile rubber

NMR

Nuclear magnetic resonance

O2

Oxygen

PA

Polyamide(s)

PAI

Polyamide-imide(s)

229

Engineering Plastics PANI

Polyaniline

PAS

Polyarylene sulfone

PBA

Poly-n-butyl acrylate

PBT

Polybutylene terephthalate

PC

Polycarbonate

PDMS

Polydimethylsiloxane

PE

Polyethylene

PEAK

Polyacryl ether ketone

PEEK

Polyether ether ketone

PEI

Polyether-imide(s)

PEO

Polyethylene oxide

PES

Polyether sulfone

PET

Polyethylene terephthalate

phr

Parts per hundred rubber

PI

Polyimide(s)

PLA

Polylactic acid

PMMA

Polymethyl methacrylate

PMR

Polymerised monomeric reactant

POM

Polyoxymethylene

PP

Polypropylene

ppm

Parts per million

PPO

Polyphenylene oxide

PPS

Polyphenylene sulfide

230

Abbreviations PPY

Polypyrrole

PS

Polystyrene

PSU

Polysulfone

PTFE

Polytetrafluoroethylene

PTI

Proof tracking index

PtRu

Platinum-rubidium

PU

Polyurethane(s)

PVA

Polyvinyl alcohol

PVC

Polyvinyl chloride

PVDF

Polyvinylidene fluoride

PVF

Polyvinyl fluoride

PVP

Polyvinyl pyrrolidone

PXD

Polyoxylenyl disulfide

PXM

Polyoxylenyl sulfide

RET

Reactive-ethylene-terpolymer blend

RL

Rockwell L hardness

RM

Rockwell M hardness (hard)

RR

Rockwell R hardness

RSSP

Recoverable shear strain parameter

SA

Shore A hardness (soft)

SD

Shore D hardness

SEBS-g-MA

Styrene-ethylene-butylene-styrene, grafted with maleic anhydride

231

Engineering Plastics SEM

Scanning electron microscope/microscopy

SiC

Silicon carbide

SMP

Shape memory polymer

sPAS

Sulfonated polyarylene sulfone

SPM

Scanning probe microscopy

SWCNT

Single-walled carbon nanotube(s)

TEM

Transmission electron microscopy

Tg

Glass transition temperature(s)

TG-MS

Thermogravimetry - mass spectrometry

TGA

Thermogravimetric analysis

Tm

Melting temperature

TMA

Thermo-mechanical analysis

TPO

Thermoplastic olefin

Ts

Softening temperature

UHMWPE

Ultra-high molecular weight polyethylene

UL

Underwriters Laboratories

UNI

Ente Nazionale Italiano di Unificazione - Italian standards organisation

UV

Ultraviolet

VCM

Voice coil motors

VDE

Association for Electrical, Electronic and Information Technologies

VGCF

Vapour grown carbon-fibre

XLPE

Crosslinked polyethylene

232

Abbreviations

233

Engineering Plastics

234

I

ndex

1-Pentyl-2,5-pyrrolidinedione, 20-22

A Abrasion, 5, 12, 125, 129, 195 resistance, 12, 125, 129 Absorb, 140, 187-188, 196 Absorbance, 73, 203-204 Absorption, 5, 10, 12, 25, 105-106, 108, 126, 138, 140, 155, 167, 191-192, 196-197, 203-204 Acceleration, 145, 150-151 factor, 150-151 abcd Acid, 19, 23, 27, 106-107, 110-113, 133, 176, 194, 206 Acidic, 113 abcd Acoustic emission, 146 Acrylate-styrene-acrylonitrile, 130, 138 abcd Acrylic, 16, 132-133 acid, 133 abcd Acrylonitrile, 1, 5, 8-9, 11, 27, 58, 95-96, 110, 130, 138-139, 186, 208-209 -butadiene-styrene, 4-5, 8-9, 16, 26-27, 37, 58, 63, 95-96, 108, 111, 115, 129a b c d 130, 138, 168, 183, 186, 188 abcd Activation, 74, 112, 146, 148, 150 energy, 74, 112, 146, 148, 150 a Active packaging, 141-142, 196 Additives, 14, 23, 31, 34, 114, 122, 134-135, 139, 155, 157, 161, 164, 166, 170, α฀β฀χ฀δ 196, 206, 213 Adhesion, 33, 37, 119, 125, 162, 165, 191 ❁ Adhesive, 18, 34, 127, 191 Ageing, 21-22, 64, 145-146, 189 Agent, 34, 38, 42, 99, 112, 145, 178-179, 206-207 Air conditioning, 1, 187 Alignment, 36, 73 Aliphatic, 141, 163

235

Engineering Plastics Alkali, 111-112, 146 Alkaline, 111, 113, 150 Alkyd resin, 8, 92 Alliance, 210, 213-214 Alloy, 4-5, 8, 95, 160, 183 Alternating current, 98, 108 Aluminium, 18, 24, 27, 29-30, 37, 57-58, 64-65, 132, 175, 178-179 American Iron and Steel Institute, 128 American Society for Testing and Materials, 7, 9, 42, 62, 64, 85, 131, 133, 135, 140, 152-155, 166 Amorphous, 12, 20, 59, 61-62, 67, 72, 74-75, 131, 140-141, 195 phase, 140-141, 195 polycarbonate composites, 131 polymers, 67 Ampliier, 197-198 Amplitude, 70, 131, 197, 200 Analysis, 16-18, 23, 33, 37, 46, 57, 59-60, 63, 66, 68, 71, 73, 79, 84, 86-87, 107, 109, 112, 132, 134-135, 144-146, 149-151, 157, 166-167, 174-175, 189-190, 197 Annealing, 20, 35-36, 202 Application, 42, 70, 80, 91-92, 129, 131, 137, 144, 146, 168, 183, 187, 189, 194, 202 Applied Physics Laboratory - John Hopkins University, 177 Applied stress, 17 Aqueous, 107, 111, 113 Arc resistance, 97-98, 104-105, 107 Aromatic, 2, 18, 23, 139, 176 Association for Electrical, Electronic and Information Technologies, 98, 116 Atmosphere, 19, 135, 141, 196 Atmospheric pressure, 152 Atomic force microscopy, 132-133 Autoclave, 152, 174, 176 cure, 174 Autoclaving, 63, 152

B Band, 108, 113, 202, 204 Barium sulfate, 27 Barrier, 140-141, 192, 195-196, 201-202, 206 properties, 140-141, 195-196, 202

236

Index Battery, 1, 3, 41, 111, 193-194 Bearing, 5, 26, 165, 190, 192 Bend, 34, 145 Bending, 16, 57, 131, 179, 197, 200 Biological, 206 Blend, 16, 19, 58, 63, 68, 73, 78, 106, 191 Blending, 19, 35, 38, 161 Block, 23, 35, 106, 115, 134 copolymer, 35 Board, 64, 99, 145, 178 Boiling, 62 Bond, 18, 190, 196 Bonding, 33-34, 38-39, 191, 196 Branched, 71-72, 166 Brittle, 9, 13, 34, 54, 62 Brittleness, 62, 85 temperature, 62, 85 Brownian motion, 74 Building, 3, 5, 25, 32, 64, 85, 157, 188-192, 210 Bulk, 36, 67, 74, 133, 162-163, 194 moulding compound, 163, 194 Butadiene, 1, 5, 7, 9, 27, 58, 96, 110, 130, 139, 186, 208-209

C Caesium bromide, 27 Calcium carbonate, 1, 7, 17, 24, 26, 29, 31, 38-39 Calcium hydroxide, 147, 149-151 Calorimetry, 20, 46, 59, 87, 141, 157, 190 Capacity, 58, 68, 71, 143, 189, 191, 197, 199, 202 Capillary rheometry, 60 Carbon black, 34, 40, 64, 104, 106-108, 110-111, 136, 193 Carbon dioxide, 142-144, 196-197, 200-202 Carbon ibre(s), 11, 24, 26, 28-31, 36-37, 41, 53, 55, 80, 92, 95, 100, 105-108, 110, 135, 137, 160, 163, 173, 175-180, 183-186, 191 Carbon nanoibre(s), 37, 39, 110 Carbon nanotube(s), 24, 33-34, 36-37, 39-40, 80, 105-106, 114, 194 Catalysis, 168 Catalyst, 134, 206 Cell, 16, 64, 189, 193-194, 197, 206, 210 Cellular, 42, 64, 66, 85, 191

237

Engineering Plastics Cellulose acetate, 8 Ceramic, 57, 65, 110 Ceramic powder iller, 57 Chain, 14, 18, 20-23, 35, 59, 70, 72, 74, 82, 112, 136, 140, 193 Chamber, 57, 165, 197, 200 Char, 19, 65, 175 Characterisation, 18, 32, 80, 109, 132, 194, 197, 201-202 Chemical, 3, 10, 12, 14, 19, 24, 26, 32, 36, 38, 58, 61-64, 84, 89, 113, 119, 132, 135-138, 141, 156, 160, 162-163, 165-166, 171, 175, 180, 187-188, 191, 195196, 202, 206, 211 attack, 191 industry, 202 resistance, 10, 19, 32, 58, 137, 163, 165-166, 187-188, 206 structure, 202 Chemistry, 44-45, 84, 88-90, 116-118, 121-122, 155, 176, 194 Chlorinated, 9, 13, 96, 138, 160, 209 Chlorotriluoroethylene, 2, 4-5, 9, 55, 96, 130, 137-138, 140, 185-186, 209 Chromatographic analysis, 79 Chromatography, 20, 146, 164 Clarity, 134, 161 Clay, 1, 26-27, 36-37, 40-41, 66, 106, 192 Clear, 134-135 Co-crystal peak, 73 Coated, 64, 107, 114, 162 Coating, 104, 115, 132, 162, 177, 192 Coeficient, 4, 14, 18, 23, 36, 54, 57-58, 68, 71, 127-129, 131-132, 134, 143-144, 149-150, 180, 198, 200, 202-205 of expansion, 57, 68 of friction, 14, 23, 127, 129, 131-132, 134 Coil, 65 Colloid, 84, 123 Colour, 111, 207 Combustion, 105, 160, 165 Compatibility, 17, 189 Compatible, 167 Complex, 114, 133, 162, 175 Component, 73, 102, 108, 114, 132, 136-137, 164-167, 189, 191 Composite, 33, 38, 43, 48, 50, 64-65, 71, 87-88, 104, 106, 110, 114-116, 118119, 126-128, 131, 135, 144, 152-153, 166, 174-179, 190-191, 194 Composition, 64, 80, 114, 135

238

Index Compound, 10, 18, 38, 65, 161-163, 168, 176, 186, 194 Compounding, 157, 170, 213 Compressed, 15, 66, 114 Compression, 2, 16, 23, 26, 32-33, 39, 41-42, 59-60, 108, 131, 136, 145, 176, 179, 206 modulus, 108 moulding, 39 Computer, 14, 37, 58, 70, 199 Concentration, 14, 18-19, 37, 42, 59, 73, 107, 112, 136, 141, 143-144, 152, 197198, 200-201, 204, 206 Conditioning, 1, 187 Conduction, 65, 108, 112, 114-115 Conductivity, 23-24, 37, 57, 64-67, 85, 97, 106-107, 110-115, 145, 161, 177, 188-189, 192-194, 197, 206 Construction, 3, 64, 74, 115, 147, 149-150, 157, 161, 175, 177-179, 190, 192, 195, 210 Consumer, 106, 168 Consumption, 190 Contamination, 98, 131, 167 Continuous, 19, 54, 76, 103-104, 113, 126, 134 Contraction, 34, 57, 69 Contrast, 132, 136 Conversion, 85, 137, 146, 206 Cooling, 3, 25, 36, 53, 59, 160 Cooperative main-chain motions, 70 Copolyester, 188 Copper, 27, 64-65, 110, 114-115, 166 Core, 19, 174, 179 Correlation, 20-21, 107, 126, 145-146, 149-151 Corrosion resistance, 114, 176 Cosmetics, 195-196, 206 Coupling, 38, 140, 151 Crack, 35, 153, 191 Cracking, 12-13, 34, 131 Crankshaft rotation, 70, 72 Crazing, 16, 136 Creep, 14-16, 19, 35-37, 74, 131, 144, 164-165, 188, 190, 210 resistance, 16, 36, 165, 188 strain, 35, 210 Crosslinked, 5, 7, 18, 53-54, 94, 107, 130, 135, 138, 167, 186, 193, 208-209

239

Engineering Plastics polyethylene, 94, 107-110, 129-130, 167-168, 186, 208 Crosslinking, 41, 193 Crystal, 35, 73, 126-127, 162, 188 Crystalline, 17, 19-20, 35-36, 58-59, 62, 67, 71-72, 104, 110, 127, 131, 141, 166, 187, 193 polymer(s), 20, 59, 110, 166, 187 Crystallinity, 17, 36, 40, 59, 140-141, 143, 187, 193, 202 Crystallisation, 14, 17, 35-36, 39, 58-60, 62, 161-162, 187 Crystallite, 73 Cure, 109, 174, 177 Cutting, 19, 67 Cyclic, 20-21 Cylindrical, 65, 67, 197 Cylindrical orthotropic thermal conductivity, 65

D Damage, 98, 125, 135, 163, 192, 207 Damping, 72, 162 Data, 17, 35, 65, 80, 97-98, 105, 109, 112, 131, 134, 145-146, 149-151, 157, 161, 174, 200-201, 205 Decay, 144, 207 Decomposition, 61, 74, 80-81, 84, 146 Deformation, 14, 17, 32, 63, 70, 130, 134, 144, 203 Degradation, 19-21, 23, 40, 50-51, 62, 79-83, 88-90, 98, 110, 112, 121-122, 136137, 141, 148, 150-151, 154-155, 162, 164, 169, 193, 202 temperature, 40 Degree of crosslinking, 41 Degree of crystallinity, 141 Degree of orientation, 134 Density, 5, 9, 15, 36, 56-57, 66, 71, 96-97, 101, 106, 114, 125, 129, 161-162, 167, 186, 192, 194, 197, 206-209 Detergent, 11-13, 137-138 Detergent resistance, 12-13, 137-138 Deterioration, 29-30, 34, 104-105, 136, 146, 153, 162, 201-202, 207 Deutsches Institüt für Normung, 58, 64, 84-85, 133, 140, 155 Diallyl isophthalate, 92, 138, 208 Diallyl phthalate, 13, 92, 103, 138 Diblock copolymer, 68 Die, 121 Dielectric, 3, 10-13, 61, 68, 73-74, 80, 93-94, 97-105, 107-109, 174

240

Index thermal analysis, 68, 70, 73-75, 109 Differential scanning calorimetry, 20, 33, 36, 38-39, 59-61, 68, 70-71, 141, 146 Differential thermal analysis, 59, 68, 70, 73 Diffraction, 36, 143, 202 Diffusion, 18, 64, 141-145, 189, 195-196, 198-206 Diffusion solubility, 142 Diffusivity, 64-67, 143, 197, 199, 202 Diglycidyl ether, 34 Dilatometry, 68 Dimensional stability, 13, 17, 19, 24-25, 58, 63, 162, 164-166, 187-189, 206 DIN-7708, 140, 155 DIN-53464, 58, 84 Direct current, 84, 108 Direct methanol fuel cell, 194 Directive, 142 Disc, 65, 67, 126-127 Dispersion, 16, 33-34, 36, 108 Dissipation, 12-13, 94, 97, 99, 104-105, 109 Dissolution, 142, 196 Distortion, 10, 12-13, 54, 63, 76, 165 Distribution, 18, 82, 107, 131-132, 164, 207 Doped, 109-111, 113 Dose, 135, 207 Draw, 15, 23, 57 Drive, 42, 196 Drying, 63, 163-164 Ductile, 9, 13, 34, 161 Ductility, 36, 126 DuPont, 164-165 Durability, 62, 145-146, 151, 157, 161, 194 Dynamic(s), 14, 17-18, 23, 32, 57, 60, 63, 68, 70-71, 127, 130-131, 144, 153, 166,169, 175, 178, 190 mechanical analysis, 17, 19, 33, 37, 63, 68, 70-72, 74, 144-145, 166-167, 190 mechanical thermal analysis, 60, 68-70

E Edge, 34, 167, 179 Eficiency, 33-34 Elastic, 33, 37, 40, 57, 108, 133, 165 modulus, 37, 40, 57 241

Engineering Plastics Elastomer, 5, 8, 12, 16, 55, 108, 135, 159, 166, 184, 188 Electric, 3-4, 36, 66, 93, 98, 108-109, 111, 193, 197 Electrical, 1, 3, 7, 12-13, 16, 19, 24, 37, 41, 61, 73, 91-95, 97-117, 119, 121, 123, 127, 136, 140, 161, 187, 193 Electrically conducting polymer(s), 111, 114-115 Electricity, 98, 193-194 Electrolyte, 107, 111 Electromagnetic shielding, 106 Electron, 19, 39, 104, 112, 131, 134-135, 196, 210 Electronic, 57-58, 91-92, 100, 102, 104, 106, 111, 187 Elongation, 3, 7, 10-14, 19, 23, 30-31, 34, 38, 40-41, 99-100, 107, 126-127, 165, 209 at break, 10, 12, 30-31, 34, 38, 40-41, 209 Embedded, 36, 66, 151 Emission, 25, 146, 160 Emulsion, 112-113 polymerisation, 113 Encapsulated, 92, 202 Encapsulating, 65 Encapsulation, 4, 92 Energy, 9, 11, 13, 73-74, 93, 97-98, 109-110, 112, 126, 131, 146, 148, 150, 162, 167, 188, 196 Engine, 4, 32, 74, 159, 163-166, 169, 173, 176 Engineering, 1-8, 10, 12, 14, 16-20, 22-26, 28-36, 38, 40-52, 54, 56, 58, 60-62, 64-66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86-94, 96, 98-100, 102, 104, 106, 108, 110, 112, 114, 116, 118-120, 122, 124, 126, 128, 130, 132, 134-136, 138, 140, 142, 144, 146, 148, 150, 152-174, 176, 178, 180, 182-214 Ente Nazionale Italiano di Uniicazione - Italian Standards, 133, 177 Environment, 44, 144, 162, 177, 194, 196 Environmental, 12, 137, 151, 167 stress cracking, 12 Epoxy prepreg, 179 Epoxy resin, 16, 18, 27-29, 33-34, 57, 68-69, 77, 103, 105-108, 110, 113-115, 177-178 Equilibrium, 141-142, 144, 196, 204 Equipment, 3, 25, 57, 62, 81, 111, 167, 175, 187 Ethanol, 140 Ethylene, 2, 4-5, 7, 9, 12, 17, 23, 25-27, 35, 40, 54-56, 58, 60, 62, 76-77, 92, 94, 96, 99, 101-102, 106-107, 110, 129-130, 137-138, 140, 159-160, 162-163, 184-186, 191, 193, 196, 202, 206, 208-209

242

Index -acrylate, 17 -chlorotriluoroethylene, 2, 4 -methacrylate, 106 acid, 23 -propylene, 2, 4-5, 25, 27, 40, 54, 58, 77, 92, 94, 99, 107, 129-130, 137-138, 140, 159-160, 162-163, 185-186, 208-209 copolymers, 58 diene, 27, 40, 107, 162 monomer grafter with tris(2-methoxyethoxy)vinylsilane, 107-108 terpolymer, 40, 107-108, 162, 167 rubber, 112, 163 -tetraluoroethylene, 2, 4, 25, 96, 185 -vinyl acetate, 8-9, 24, 26-27, 40, 54, 56, 63, 94, 96, 101, 110, 129-130, 138, 208-209 -vinyl alcohol, 140-141, 144, 202 European Norms, 64, 85, 156 Evaluation, 32, 36, 60, 62, 116, 134, 144, 166, 174, 190 Expanded, 64, 66 Expansion, 3-4, 18, 23, 33-34, 36, 53-54, 57-58, 68-69, 71, 104, 167, 188 coeficient, 4, 18, 57-58, 68, 71 Exposure, 61, 63, 74, 77, 111, 136-137, 146, 148-152, 154, 162, 164, 207-208, 210 life, 137 time, 148-149 Extension, 15, 57, 69 Extraction, 20-21 Extrusion, 19, 39, 59, 134, 167-168

F Fabbrica Italiana Automobili Torino - Automootive Standards, 133 Fabric, 33, 65, 177 Fabrication, 14, 41, 93, 102, 144, 164, 168, 175, 187, 195 Failure, 33-34, 110, 125-126, 131, 145, 168, 178-179, 196 Fatigue index, 12, 129-130 Fatigue loading, 130-131 Fatigue resistance, 187-188 Fibre, 1, 8, 11, 13, 23-26, 28-39, 41, 53-55, 64-67, 80, 92, 95-96, 99-100, 104108, 110, 126-132, 135, 137, 146, 149, 153, 157, 159-164, 166, 173-180, 183186, 188, 190-192, 210 -reinforced phenol-formaldehyde resins, 66 -reinforced plastics, 146

243

Engineering Plastics Fibrous, 114 Fickian diffusion, 142, 205 Filled, 7, 10, 29, 35-36, 38, 41, 54, 58, 65, 68, 71, 104, 106-108, 110-111, 114115, 138, 159, 161, 184-186 Filler, 26-27, 36, 38, 57, 59, 104, 108, 114, 126, 194 Film(s), 18-19, 39, 41, 58, 66, 110, 115, 119, 131, 133-135, 140-144, 153-154, 191, 193, 195, 201-206 Finite element analysis, 16, 37, 167, 175 Fire, 97-98, 115-116, 159, 186, 189-190, 210 Firing, 192 Flame retardant, 23, 109, 163 Flammability, 12-13, 192 Flexibility, 40, 177 Flexible, 64, 67, 107, 184, 186, 188 Flexural, 3, 7, 10-13, 17, 29-30, 32-34, 38-39, 80, 99-100, 136, 177, 190, 195, 210 modulus, 3, 10, 12-13, 29-30, 32, 34 Flow, 39, 57-59, 97-98, 109, 143, 163, 165, 174, 190, 206 Fluid, 98, 160, 187 Fluorinated ethylene-propylene, 2, 4, 25, 58, 77, 92, 99, 130, 137-138, 140, 185 copolymer, 99, 130, 138, 140 Fluoropolymers, 40 Flux, 65, 85, 175 Foam, 15-16, 37, 64, 66, 85, 156, 167-168, 188-190, 192, 206, 210 Food, 67, 141-142, 195-196, 201-202, 206-207 packaging, 141, 201-202, 206 Force, 37, 57, 69-70, 131-132, 135, 175-176, 179 Formation, 19-22, 65, 114, 126, 133-134, 175, 196 Formulation, 16, 29, 36, 41, 99, 114, 176, 206 Fourier-Transform infrared spectroscopy, 20, 33, 202, 204-205 Fraction, 20, 36, 38-39, 108, 143, 162 Fracture, 3-4, 25, 111, 139-140, 159-160, 162, 166, 168, 170, 193-194 Functionalisation, 194 Functionality, 168

G Gamma irradiation, 210 Gas(es), 16, 20, 62, 64, 79, 82, 141-144, 146, 148, 189, 195-200, 202, 206 chromatography, 20-21, 146 concentration, 143-144, 198, 200

244

Index diffusion coeficient, 144, 198 Gaskets, 5, 144, 183, 185 Gear, 3, 25, 160, 176-177, 187-188 Gel(s), 108, 134, 164 permeation chromatography, 164 General purpose, 7, 54-56, 94-96 Glass, 1, 7-8, 10, 13, 17-18, 23-25, 28-38, 41, 53-55, 58, 61, 65, 67, 69, 92, 9596, 99-100, 104, 108-109, 126-131, 133, 135-137, 140, 146, 149, 159-164, 166, 173-174, 176-177, 179, 183-188, 190-191, 199, 210 ibre, 1, 13, 24-25, 28-32, 35, 37-38, 53-55, 65, 92, 99-100, 104, 108, 126-131, 137, 146, 149, 159-164, 166, 173-174, 179, 183-186, 188, 191, 210 -reinforced plastics, 146-147, 149-151 transition temperature, 23, 33, 35-36, 38, 40, 61, 67-71, 73-74, 81, 83, 109, 140, 176-177 Glassy, 162, 196 Glazing, 3, 5 Gloss, 134, 168 Gold, 27 Grade, 7, 17, 54, 94, 98, 136, 165-166, 184, 188 Gradient, 64, 97, 197 Grafted, 19, 27, 35, 107, 193 Grafting, 35, 193 Gross surface crazing, 136 Growth, 14, 142, 153, 187, 191 Guarantee, 174

H Half-sorption time method, 142, 205 Handling, 62, 169, 174, 201 Hardening, 15-16, 178-179 Hardness, 7, 9, 16, 37, 125-126, 132-133, 161 Haze measurements, 133 Heat, 3-4, 10-13, 19-20, 25, 37, 53-54, 57-59, 62-63, 65-68, 71, 76-77, 85, 97, 112-113, 115, 134, 143-144, 161, 164, 168, 175, 188, 190, 192, 196-197, 199, 202 build-up, 57 distortion temperature, 12, 19, 63, 76 low, 59 resistance, 12-13, 59, 97 Heating, 3, 53, 59, 66, 68, 70, 73, 75, 79, 82, 106, 146, 160, 187, 192, 197

245

Engineering Plastics rate, 59, 68, 70, 75, 79, 146 Heterogeneous, 113, 161 Hexamethylene diisocyanate, 18 High-density, 71, 161 polyethylene, 5, 7, 9, 14, 54, 56-57, 59, 62, 65-67, 72, 78, 94, 101, 106-108, 110, 114, 129, 134-136, 138, 140, 162, 186, 191 High-impact polystyrene, 134 High molecular weight, 2, 4, 14, 20, 96, 113, 126, 162, 164, 186 High-pressure, 73 High-speed, 134 cameras, 134 High temperature, 13, 35, 53, 74, 76, 81, 100, 102, 104, 177, 194 History, 196, 202 Homogeneous, 189 Hoses, 4, 160, 164, 183, 186 Hot-melt, 191 Housing, 25-26, 37, 42, 91-92, 114 Humidity, 98-99, 113, 127, 135, 196 Hybrid, 37, 112, 190 Hydraulic, 3, 25, 160, 177 Hydrocarbon, 202 Hydroluorocarbons, 64, 206 Hydrogen peroxide, 113 Hydrogenated, 68, 168 Hydrolysis, 12, 141 Hydrolytic stability, 10-11, 32, 138, 140, 163 Hydrophobic, 202

I Identiication, 10, 12, 167 Imaging, 132, 140 Immersion, 140, 152 Immiscibility, 106 Impact, 3, 5, 7, 9-17, 19-20, 24, 31-39, 44, 61-63, 72, 85, 99-100, 134, 136-137, 144, 160-161, 163, 165-166, 168, 195, 207-208 resistance, 144, 166, 168 strength, 3, 9, 11-14, 17, 31, 34-38, 100, 136-137, 161, 195, 207 Impedance, 108, 175 Implantable, 195-196 Impregnated, 33, 177

246

Index Impurities, 107 In situ, 18, 114 In-plane, 18, 33 Indicator, 134 Induction, 20-21, 168 Industry, 25, 81, 84, 115, 152, 155, 160-161, 163-164, 167, 174, 176, 189, 192, 202, 206-207, 210-214 Infrared, 14, 20, 33, 70, 73, 112, 174, 196, 202, 204-205 spectra, 202 spectroscopy, 14, 73, 202 Infrastructure, 190 Injection, 4, 19, 23, 35-37, 39, 58-59, 81, 108, 160-161, 166, 168 moulding, 19, 23, 37, 39, 58-59, 81, 108, 161, 168 Inorganic, 107 Institute, 153, 157 Instrument, 4, 25, 133-134, 159, 161, 174 Instrumentation, 109, 189, 197, 207 Insulated, 174 Insulation, 1, 4, 24, 64, 67, 85, 91-92, 97, 102, 110, 156, 188-189, 192, 206, 210 properties, 64, 192 Insulator, 19, 67, 97-98 Intelligent packaging, 142, 196 Intensity, 72, 162 Interest, 77, 114, 141, 201 Interface, 123, 162, 175, 191 Intermedidate, 132-133, 188 Internal stress, 68 International Organization for Standardization, 133 Intrinsic, 36, 163-164 viscosity, 164 Ion, 83, 115, 135, 193-194 Ionic conductivity, 194 Irradiated, 193 Irradiation, 162, 193, 196, 207, 210 Isoprene, 27, 41 Isotactic, 70 Isotherm, 205 Isothermal, 16, 109 Isotropic, 17

247

Engineering Plastics Izod, 7, 9-13, 31, 38-39, 100, 136

J Jar, 154 Jet, 3, 74, 173, 175 Johnson-Kendall-Roberts theory, 135 Joint, 195 Jute, 27, 111

K Kevlar, 109, 173 Key, 37, 161, 174, 196 Kinetic, 146, 153

L Lamellar, 14, 133-134 Laminate, 7, 10, 191 Large scale, 74, 140 Laser, 18, 66-67, 196-197 lash technique, 66-67 Layer, 133, 135, 162, 202 Legislation, 167 Light, 18, 115, 133-134, 136, 154, 197-199 scattering, 18, 133-134 Linear, 26, 57, 59, 61, 69, 71-73, 106, 131, 133, 146, 148, 166, 191 low-density polyethylene, 106 Liquid, 19-20, 34, 58-59, 74, 110, 126-127, 162, 166, 187-188, 196 crystalline, 19-20, 58, 110, 127, 166, 187 polymer, 19-20, 127 Load, 5, 125-128, 130-131, 135, 151-152, 169, 178, 188, 190-192, 196 Loading, 17, 36, 39-40, 63, 65, 70, 130-131, 164, 175, 190 Logarithm, 133, 146, 148 of the recoverable shear strain parameter, 133 Long glass ibre, 13, 92, 131, 161, 185, 188 -polypropylene, 161 Long-term, 32, 35, 61, 64, 144-146, 151-152, 162, 189-190, 192, 195, 210 creep, 35 Loss, 18-19, 22, 36, 38, 40, 61, 63, 70-77, 79-80, 97-98, 109, 125-126, 137, 146, 152, 179, 191, 204, 207 factor, 73-75, 98

248

Index modulus, 36, 38, 40, 70-72 Low-density, 71, 114, 125 polyethylene, 5, 9, 12, 26, 39, 54, 56-57, 59, 62-63, 65-68, 72, 94, 96, 101, 106, 109-110, 115, 125, 129, 133-134, 136-138, 142-144, 162, 186, 188, 192, 197, 200-205, 208-209 Low molecular weight, 20, 141, 164, 195 Low temperature, 62, 70, 72, 161, 168 embrittlement, 62 Lubricant, 32, 42, 163, 184

M Machine, 3, 32, 42, 84, 134, 156, 161, 169, 187, 196 Macro-scale friction coeficient, 131 Macromolecular, 47, 49-51, 87-89, 117-118, 203-205, 213 Macroscopic, 161-162 Magnetic, 68, 140-141 resonance imaging relaxometry, 140 Main chain, 23, 72, 74 Manufacture, 37, 41, 61, 81, 99, 110, 159, 164, 174, 187, 193 Manufacturing, 46, 84-86, 116-117, 120, 170, 174, 178-180, 194, 196 Market, 14, 142, 163 Mass spectrometry, 20-21, 81, 83, 135, 146 Material, 9, 11, 13-16, 19-22, 35, 57-59, 61-71, 73, 93, 97-99, 109, 111, 114, 125-127, 131-132, 136-137, 144-145, 148, 154, 162-163, 165-168, 174-175, 177, 187-188, 190-192, 194-195, 197, 202, 207 is brittle and does not exhibit a yield point, 13 is ductile and does not exhibit a yield point, 13 Matrix, 20, 33-34, 36-39, 59, 64, 71, 107-108, 114, 157, 161-162, 177, 179, 191, 194, 204 Maximum operating temperatures, 61-63 Measurement, 18, 32, 57-58, 62, 64, 67-69, 107-109, 130-133, 142, 145, 196 Mechanical property(ies), 3, 7, 9-11, 13-15, 17, 19-25, 27-29, 31-41, 43, 45, 47, 49, 51, 61, 65, 67, 80, 97, 99-100, 104, 126-127, 136-137, 140, 161, 174-175, 177, 192, 194-195 strength, 189 Mechanism, 32, 62, 70, 108, 125, 134, 141, 148, 150, 195, 197, 200 Medium-density poylethylene, 39 Melt, 17, 23, 35-36, 38, 54, 59, 61, 133, 163-164, 191-192 low index, 163 rheology, 133

249

Engineering Plastics temperature, 17, 36, 38, 59-61, 73 viscosity, 164 Melting, 14, 57, 59, 61, 67, 72, 141, 165, 193 point, 57, 59, 67, 72, 141, 165 temperature, 59, 61, 193 Membrane, 142, 193-194, 196 Mercury Surface, Space, Environment, Geochemistry and Ranging, 177 Metallic, 107, 114, 125, 154 Metallocene-catalysed, 133 Methacrylate dental resins, 133 Methodology, 142, 201-202 Methyl group, 16 Methylene dianiline, 176 Micro-cracks, 136 Micro-scale friction force, 131-132 Micrometer, 134 Microscopy, 19, 39, 104, 127, 131-132, 134, 196 Microstructure, 39 Mineral illers, 105 Mixed, 14, 34, 37, 64 Mixing, 104 Mixture, 36, 113 Model, 14-15, 65, 132, 145, 148 Modelling, 145, 175, 189, 193 Modiication, 41, 168 Modiied, 23, 36-37, 40, 57, 63, 110, 141, 146, 149, 152, 162-163, 177, 194, 196, 203-204 clays, 40 Modulation, 132, 200 Moduli, 29, 33 modulus, 3, 7, 10-13, 16, 18-20, 23, 29-30, 32-34, 36-41, 57-58, 68, 70-72, 108, 126, 144, 161-162, 190-191, 210 Moisture, 10, 97, 140, 187, 191, 196, 202 Molecular structure, 111 Molecular weight, 2, 4, 14, 17-20, 60, 96, 113, 126, 133, 141, 145, 162, 164, 186, 195, 207 distribution, 18, 164 Molybdenum disulide, 1, 42, 184-186 Monitoring, 142, 174, 200, 202 Monomer, 107, 113

250

Index Montmorillonite, 27, 37, 40, 63, 66, 106, 110, 115 Morphology, 14, 35-36, 39, 104, 125-126, 140, 202 Motion, 70, 72, 74, 125 Motor, 3, 64-65, 91-92, 167, 175 Mould, 12, 36-37, 54, 57-59, 76, 103, 165, 168, 174, 187-188, 206 shrinkage, 12, 57-58, 188 Moulded, 4, 23, 35-37, 57, 59, 84, 160, 163, 167, 176, 187-188, 192 Moulding, 10, 17, 19, 23, 35, 37, 39, 58-60, 62, 81, 84, 108, 155, 161, 163165, 168, 174, 186, 194 compound, 163, 186, 194 Multifunctional, 180 Multi-walled carbon nanotube(s), 34, 36, 39

N Nanocomposite, 19, 36, 39, 175, 177 Nanoparticle, 34 Nanotechnology, 84 National Aeronautics and Space Administration (The), 176-177 Natural rubber, 27, 41, 108 Network, 23, 66, 114 formation, 114 Nickel-cobalt-zinc ferrite, 27 Nitrile rubber, 168 Nitrogen, 8, 34, 61, 68, 76, 79-80, 84, 112, 115 Noise, 71, 166-167, 188 Non-polar, 112-113 Not reported, 11, 56, 96 Notched, 7, 9-13, 34, 38-39, 165 Izod impact strength, 9, 11, 13 Novolac resins, 115 Nozzle, 65, 175 Nuclear magnetic resonance, 68, 141 spectroscopy, 68, 141 Nucleated, 133 Nucleation, 36, 162 Nylon, 8, 34, 71, 95, 98, 101, 164, 187, 199, 206

O O-rings, 5, 160, 183, 186 Opaque pigments, 136

251

Engineering Plastics Optical, 18, 58, 80, 127, 134-135, 196 microscopy, 127, 134, 196 properties, 18, 134-135 Optimisation, 59, 166 Organic, 43, 62, 110, 113, 115, 136, 141, 192 solvent, 113 Orientation, 18, 39, 58, 98, 108, 134 Oriented, 14, 20, 33, 133-134 Oscillation, 97 Outdoor weathering, 135-136 Oven, 3, 53, 177 Owens-Wendt method, 131 Oxidation, 20-22, 63, 111, 114-115, 136, 151-152, 168 resistance, 114-115, 152 Oxidative, 68, 110, 113, 152 degradation, 110 stability, 68, 152 Oxygen, 7, 13-15, 19, 79, 110, 112, 142-144, 152, 190, 196-197, 200-221, 204206 Ozone, 206

P Packaging, 42, 48, 62, 81, 84, 123, 138, 141-142, 155, 169, 196, 201-202, 206 Packing, 35, 195 Paint, 63, 154 drying, 63 Panel, 161, 177, 179 Paper, 44, 48, 51-52, 86-88, 114, 116, 119, 125-126, 145, 154, 156-157, 170171, 180-181, 191, 210-214 Particle(s), 17, 34, 38-39, 108, 110, 114-115, 125-126, 134, 136 size, 17, 114, 136 Parts per hundred rubber, 40 Parts per million, 134 Pattern, 20-21, 82, 125 Penetration, 59-60, 162 Performance, 10, 12-13, 17-19, 32, 43-45, 51, 57, 62, 74, 88-89, 108, 115, 125, 136, 144-146, 161, 163-165, 167-169, 175, 180-181, 188-190, 192, 202, 214 Permeability, 140-142, 194-196, 204-206 coeficients, 142, 204-206 Permeate gas, 141, 143, 195, 197

252

Index Permeation, 140-143, 164, 195-197 Permit, 141, 195 Peroxide, 112-113, 166 Phenol-formaldehyde, 1, 63, 66-67, 94, 101, 108, 111, 129, 139, 208-209 Phenolic resin, 64, 175 Phenylene oxide, 16, 104 Phosphate, 113 Physical property(ies), 35, 41, 61, 63, 68, 74, 76, 174, 206-207 Physics, 16, 43, 47-48, 117, 120, 122, 154, 177, 211-212 Pipes, 3, 25, 183, 186 Plant, 3, 20, 26, 189 Plasma, 19, 65, 175 Plastic, 1, 12, 14, 17, 19, 24, 37, 57-58, 62, 98, 102, 108-110, 119, 132, 136, 139, 145, 153-154, 159, 161, 165-168, 177-178, 183, 187, 201, 206, 209 ilm, 119, 153-154 Plasticisation, 140 Plasticised, 9, 63, 96, 101, 139, 202 polyvinyl chloride, 63 Plasticiser, 73 Plate, 75, 85, 174, 194 Platinum-rubidium, 194 Polar, 112-113 Polarisation, 18, 109 Polyacetals, 29, 42, 94, 132, 164, 187 Polyacryl ether ketone, 17, 21, 59, 73-74, 112 Polyacrylonitrile, 110, 177 Polyamide(s), 2, 9, 19, 23, 53, 56, 80, 91, 126-132, 135, 138, 140, 159-160, 164, 166, 173, 183, 185-186, 192, 208-209 -imide(s), 2, 4, 19, 25, 28-29, 31, 42, 55-56, 60-61, 66, 74, 76, 80, 91-92, 95, 101, 103, 130, 138, 160, 173, 185-186, 208-209 Polyaniline, 65, 107-113, 115 Polyarylate(s), 2, 8, 54, 58, 94, 100 Polyarylene sulfone, 24, 194 Polybutadiene, 68 Polybutylene terephthalate, 2, 4, 25, 42, 53-54, 91-92, 94, 103, 129, 159-160, 164, 183-184, 186-187 Polycaprolactone, 24 Polycarbonate, 2, 4-5, 8-9, 16, 25-26, 28-30, 54, 56, 58, 63-64, 73, 91-92, 94, 101, 104, 106, 110, 114-115, 129-131, 137, 139, 168, 188, 208-209 Polycondensation, 61

253

Engineering Plastics Polydimethylsiloxane, 19, 80, 107, 110 Polyester, 5, 7, 10, 16, 61, 94, 110, 132-133, 163 resin, 5, 133 amide, 130 Polyether ether ketone, 2, 5, 8-9, 17, 25-26, 28-32, 38-39, 53-54, 60-61, 63, 68, 76-77, 91-92, 94, 97, 99-100, 103-104, 106, 114, 129-130, 138, 159-160, 163, 173, 184-186, 195, 207-209 Polyether-imide(s), 2, 4, 8-9, 11, 13, 25, 30, 53, 55, 60, 63, 74, 76, 80, 91-92, 95, 101, 103, 106, 114, 127-128, 130, 138-139, 160, 184, 186, 207-209 Polyether sulfone, 2, 4, 9, 11, 25-26, 55-56, 58, 60, 62-63, 74, 76-77, 79, 81-82, 91-92, 96, 100-101, 103, 130, 138-139, 160, 173 Polyethylene, 2, 4-5, 7, 9, 17, 14, 24, 27, 34, 39, 53-54, 56-57, 64, 66, 72-73, 75, 77-79, 91, 94, 96, 101, 106-107, 109-110, 115, 125-126, 129-130, 133-134, 138, 142, 160-163, 167-168, 186, 188, 193, 202, 208-209 oxide, 24, 110, 115 sulide, 2 terephthalate, 2, 4, 8-9, 12, 17, 25, 27-32, 34-35, 54, 56, 74-75, 91-92, 94, 101102, 129-130, 132, 139, 141-144, 159-160, 163-164, 183-184, 186, 205-206, 208-209 Polyhydroxybutyrate, 24 -co-hydroxyvalerate, 24 Polyimide, 2, 4, 8-9, 18, 24-25, 27-31, 42, 55-56, 58, 60-61, 63, 74, 76-77, 80, 92, 95, 103, 109, 114, 130, 138-140, 160, 173, 176-177, 183-186, 207-209 Polyisobutylene, 208-209 polyisocyanurate, 23, 67, 189 Polylactic acid, 26-27, 106, 114 Polylactide, 68, 106, 114, 142, 204-206 Polymer, 3, 10, 12, 14-17, 19-20, 24-26, 28-36, 39-52, 54, 57-60, 62, 65-67, 70, 72-74, 76-77, 80-81, 83-92, 94, 97, 99-100, 102-107, 109, 111-112, 114-122, 125-129, 131-139, 141, 143-149, 151-157, 162, 164, 169-171, 173, 175, 177, 186, 191, 194-196, 204, 209-213 Polymeric, 1, 43, 51, 68, 70, 74, 84, 110, 114, 119, 125, 132-133, 141-142, 162, 176-177, 190, 196 Polymerisation, 112-114 Polymerised monomeric reactant, 176 Polymethyl methacrylate, 4-5, 16, 27, 40, 54, 56, 64-68, 74, 94, 96, 101, 107, 129-130, 137, 139, 159-160, 183, 186, 208-209 Polymethyl pentene, 7, 54, 58, 62, 94, 129, 138-139, 209 Poly-n-butylacrylate, 135 Polyoleins, 2, 14, 136, 144, 151, 156

254

Index Polyoxyethylene, 7, 26 Polyoxylenyl disulide, 82 Polyoxylenyl sulide, 82 Polyoxymethylene, 2, 4-5, 25, 42, 101-102, 138-139, 183-184, 186 Poly-p-phenylene, 106, 114 Polyphenylene disulide, 2 Polyphenylene oxide, 2, 4, 8-9, 16, 25, 53-54, 58, 94, 96, 103-104, 115, 129-130, 139, 159-160 Polyphenylene sulide, 2, 4, 9, 11, 13, 25-27, 42, 53, 55, 59-63, 65, 74, 76-77, 8183, 92, 96, 103-104, 110, 126-127, 130, 137-139, 160, 165-166, 184-188 Polypropylene, 2, 4-5, 7, 9, 15-16, 19, 25-27, 29, 31, 35, 38, 40, 53-54, 56, 5859, 62, 65-67, 70, 76-79, 91-92, 94, 100, 104, 106, 108, 110-111, 114-115, 129, 135-136, 138-139, 159-163, 166, 168, 186, 188, 193, 202, 208-209 Polypyrrole, 107, 110, 114-115 Polysilsesquioxane, 24 Polystyrene, 1, 7, 9, 16, 26-27, 38, 64-67, 108, 110, 115, 134, 136, 139, 190, 192-193, 207-209 Polysulfone, 2, 4-5, 9, 11, 13, 25-26, 55-56, 58, 60, 62-63, 74, 76-77, 91-92, 96, 101, 103, 127-128, 130, 139, 160, 173, 185-186, 209 Polytetraluoroethylene, 1-2, 4-5, 8-9, 25-26, 28-30, 32, 41-42, 55-57, 60, 62, 66, 77, 79, 95-96, 101-105, 126, 129-130, 132, 138-140, 160, 163, 183-186, 193, 196, 208-209 Polyurethane(s), 4-5, 8-9, 23-24, 27, 37, 55-56, 63-64, 66, 85, 87, 95-96, 106, 109-110, 114, 129-131, 133, 139, 156, 162, 184, 186, 188-189, 206, 208, 210, 213-214 foam, 85, 156, 210 Polyvinyl acetate, 27 Polyvinyl alcohol, 110, 115 Polyvinyl chloride, 9, 16, 27, 63-66, 96, 101, 110, 138-139, 209 Polyvinyl luoride, 2, 8-9, 11, 26-27, 40-41, 55-56, 66, 95, 130, 137, 139, 173 Polyvinyl pyrolidone, 68, 110, 115 Polyvinyl pyrrolidone, 110 Polyvinylidene luoride, 2, 4-5, 40, 53, 55, 66-67, 95-96, 115, 130, 139, 184-186, 193 Pooled Weibull distribution, 131 Pore, 146, 151, 192 Porosity, 174 Post, 17, 19, 60, 62, 177, 190 Potassium hydroxide, 17, 44, 147, 149-151

255

Engineering Plastics Potential, 34, 64, 97-98, 113, 142, 174-175, 177, 193, 206 Powder, 29-30, 57, 64-65, 67 Power, 3, 5, 25, 32, 48, 57, 97, 110-111, 132, 135, 166, 187-188, 194, 211 Precision, 5, 25-26, 35, 165, 187-1883 Prediction, 35, 65, 137, 144, 146, 151, 157 Preparation, 64, 194 Prepreg, 174, 179 Pressure, 3, 20, 25-26, 32, 36, 59, 73, 79, 114, 132, 143, 152, 166-167, 197, 205 Probe, 57, 60, 69-70, 131 Procedure, 145-146, 148, 151 Process, 14, 17, 23, 35, 39, 52, 60, 68, 87, 112, 135, 142, 144, 148, 165, 167168, 174-175, 177-179, 190, 192-193, 196-197, 204 Processability, 60, 161 Processing, 4, 13, 17, 21, 36, 62, 98, 134, 145, 174-176, 181, 207 Producer, 145 Product, 20-21, 141, 144-145, 167-168, 188-189, 195, 201-202, 206 Production, 114, 164-165, 174, 176, 190, 206 Proile, 37, 197 Proliferation, 144 Proof tracking index, 98 Property(ies), 1, 3-4, 7, 9-25, 27-29, 31-43, 45, 47, 49, 51, 53-55, 57-61, 63-69, 71, 72-77, 79-81, 83-85, 87, 89, 91, 93-95, 97-101, 103-111, 113-115, 117, 119, 121, 123, 125-127, 129, 131-137, 139-149, 151, 153, 155, 157, 161-168, 174-177, 187-197, 202, 204, 206-207, 209-210 Propylene, 2, 4-5, 25, 27, 38, 40-41, 54-55, 58, 60, 77, 92, 94, 96, 99, 101-102, 107, 129-130, 137-138, 140, 159-160, 162-163, 185-186, 193, 196, 208-209 Protection, 3, 92, 136, 177 Prototype, 144, 192 Pump, 25-26, 166, 183, 185 Pyrolysis, 62, 79, 82-83

Q Quality, 36, 58, 134, 145, 166, 168, 174

R Radiation, 3, 10, 13, 114, 135, 193, 197, 206-209 resistance, 207 Rate constant, 146 Ratio, 15-16, 23, 66, 93, 97, 112, 142, 175, 179, 196, 205 Raw material, 98, 207 256

Index Rayon, 65, 175 Reaction, 112-113, 168 Reactive-ethylene-terpolymer blend, 191 Recoverable shear strain parameter, 133 Recovery, 167 Recycle, 45 Recycled, 19-22, 37-38, 67, 107, 168, 192 Reduction, 35, 40, 111, 136, 164, 207 Reinforcement, 18, 24, 28, 34, 36, 41, 53, 104-105, 137, 146, 157, 161-164, 188 Reinforcing agent, 34, 38, 99 Relative, 19, 21-22, 113, 125, 135, 137, 196, 203 humidity, 113, 135, 196 Reliability, 143, 202 Replacement, 5, 24-25, 177, 187, 195 Reproducibility, 70 Research, 35, 46, 62, 64, 84, 108-109, 120, 125, 141, 154, 166, 174-176, 178, 192, 211-212 Residual stress, 57 Residue, 81-82, 192 Resilience, 32, 163 Resin, 5, 8, 16, 18, 27-29, 33-34, 57, 62, 64-65, 68-69, 71, 77, 92, 103-108, 110, 113-115, 133-135, 146, 154, 163, 174-178, 186, 188, 193-194, 206 transfer moulding, 174 Resist, 62, 130, 165 Resistivity or speciic resistance, 97 Resonance, 68, 112, 140-141, 178 Retention, 76, 147, 149-151 Reuse, 45, 167 Review, 1, 7, 26, 43, 110, 125, 168, 206, 212-213 Rheology, 133 Rheometry, 60 Rigid, 16, 18, 23, 25, 42, 59, 64, 66-67, 85, 156, 189, 206, 210 Rigidity, 3, 5, 115, 144, 168, 187-188, 193-194 Ring, 59 Rockwell, 9, 132-133 L hardness, 8-9 M hardness (hard), 7-9, 133 R hardness, 7-9 Room temperature, 34, 67, 93, 97, 114, 137, 140, 190, 197 Rotation, 70, 72, 74

257

Engineering Plastics Roughness, 132-134 Rubber, 27, 34-35, 41, 51, 87-88, 108, 113, 116, 118, 120, 131-134, 153, 162164, 168, 170, 210 compound, 162 Rubbery, 16, 33, 67, 162

S Safety, 5, 64, 145, 178 Sample, 36, 57, 63-65, 68-70, 79, 112, 134, 140, 143-144, 146, 162, 175, 197200, 203 Satin weave, 33 Saturation, 143, 198, 204-205 Scale, 74, 125, 131-134, 140 Scanning electron microscope/microscopy, 19, 33, 35, 39, 107 Scanning probe microscopy, 131-132 Scattering, 18, 133-134 Seal, 26, 134, 167 Sealed, 143, 197 Sealing, 167 Sectional, 97, 190 Sensitivity, 20, 69, 74, 108, 127, 131 Sensor, 204 Separation, 106, 131 Shape, 64, 66, 108, 114, 187, 204 memory polymer, 66 Shear, 15-16, 18, 33, 68, 71-72, 80, 133, 191, 196, 207 loss modulus, 72 storage modulus, 71-72 strength, 68, 80, 207 stress, 72 Sheet, 5, 10, 38, 168, 192 Shore, 9, 133 A hardness (soft), 7-9 D hardness, 7-9 Shrinkage, 12, 36, 54, 57-59, 76, 84, 103, 165, 188 Side chain, 18 Silicon, 9, 125 carbide, 125-126 Silicone, 30-31, 41-42, 92, 131, 133, 183-185 oil, 133

258

Index Simulation, 37, 189 Simultaneous, 132, 161 Single-walled carbon nanotube(s), 33 Size, 17, 73, 114, 125, 134, 136, 187 Sodium hydroxide, 147, 149-151 Soft, 9, 33, 67, 132-133 Softening, 59-60 point, 59 temperature, 59-61 Software, 166, 169, 189 Solid, 20, 58, 64-65, 74, 125, 175, 201 Solubility, 141-142, 195, 204-205 Solution, 111, 113, 147, 149-151, 168, 194, 203 Solvent, 3, 10, 16, 33, 73, 112-113, 138, 140, 176 resistance, 16, 138 Sorption, 141-142, 195, 204-205 -diffusion mechanism, 141, 195 Speciic gravity, 162 Speciic heat, 66, 68, 143, 192, 197, 199, 202 Speciication, 67, 85, 156, 174, 188, 210 Spectra, 70, 196, 202-203 Spectrometry, 20, 81-82, 135, 146 Spectroscopy, 14, 20, 33, 68, 70, 73, 112, 135, 141-142, 146, 196, 202, 212 Speed, 126-127, 134-135, 146, 163, 166, 188 Spherical, 114-115, 135 Spherulitic superstructures, 133 Spiral woven fabric composites, 65 Stabiliser, 136 Stability, 4, 10-11, 13, 17, 19, 24-25, 32-33, 36, 40, 50-51, 58, 63, 67-68, 70, 72, 80-81, 83, 88-90, 103, 108, 112, 121-122, 136, 138, 140, 152, 154-155, 162166, 168-169, 178-179, 187-190, 193-194, 206 Standard, 24, 39, 42, 64, 85, 137, 145, 152-154, 165, 174, 176, 189, 210 Static, 19, 33, 114, 131, 135, 153, 190 Steady state, 66 Sterilisation, 3, 63, 81, 195, 207 Stiffness, 3, 12, 25-26, 33, 35-36, 41, 63, 125, 165-167, 177, 188 Storage, 16, 36, 38, 40-41, 71-72, 138, 140, 210 modulus, 16, 36, 40-41, 71-72, 210 Strain, 7, 10, 12, 15-17, 23, 34-35, 37, 40, 100, 125, 133, 190-191, 194, 210 at break, 40

259

Engineering Plastics at yield, 100 Strategy, 114, 194 Strength, 3, 5, 7, 9-14, 16-26, 28-29, 31, 33-41, 58, 61, 68, 80, 93-94, 98-105, 107, 125-127, 131, 136-137, 144, 146-151, 161, 165, 176-177, 188-189, 191192, 194-196, 206-207, 209-210 Stress(es), 12-17, 20, 23, 32, 36-39, 57, 68, 72, 126, 131, 136, 144-145, 190-191 amplitude tests, 131 relaxation, 32, 144, 190 Stretching, 73, 204 Strip, 57, 167 Structure, 33, 59, 64, 72, 74, 111-112, 134, 141, 161, 174-175, 179, 189, 191, 202, 206 Styrene-acrylonitrile, 1, 130, 138-139, 208 -butadiene, 1 Styrene-butadiene, 7, 139, 208 copolymer, 139 -rubber, 27 Styrene-ethylene-butylene-styrene, 35 grafted with maleic anhydride, 35 Styrene-maleic anhydride, 1, 94, 129 Substituted, 84, 115, 144 Substrate, 36, 166, 191 Sulfonate, 110, 115 Sulfonated polyarylene sulfone, 24, 194 Sulfonation, 193 Sulfur, 9, 62, 82, 110 Sunlight, 135-137 Surface, 7, 11, 13, 15, 17, 19, 37-39, 74, 94, 97-99, 104-105, 107-108, 114, 125126, 131-137, 162, 166, 177, 188, 197 free energy, 131 haze, 133 micro-crazing, 136 resistivity, 107-108 tension, 134 Suspension, 169 Synthesis, 80, 107, 112-113, 134, 193

T Tailoring, 125, 175 Talc, 1, 24, 27, 35, 38, 58, 65, 92, 110, 115, 159, 163

260

Index Technical, 52, 87, 116, 164, 168, 170, 180, 213-214 Temperature, 4, 9-15, 17-19, 32-36, 39-40, 53-54, 57, 59-64, 66-83, 85, 93, 97, 99-100, 102-104, 109, 114, 127, 131, 137, 140, 142, 145-146, 148-150, 161, 163-165, 168, 176-177, 187, 189-190, 192-194, 197, 205-206 range, 14, 19, 40, 57, 59-60, 62, 69, 163, 165 Tensile properties, 23-24, 33, 37, 39, 42, 99, 105, 146, 191, 195 Tensile strength, 10, 12-13, 16, 18-23, 28-29, 33-35, 39-40, 58, 61, 99-100, 102, 107, 125-127, 131, 146-151, 188, 191, 194, 209 Tensile stress, 16, 126 Tensile testing, 191 Tension, 14, 33, 98, 131, 134, 136, 145, 191 Terpolymer, 16, 40, 59, 108, 129-130, 138-139, 162, 191 Test, 9, 11, 13-14, 19, 32, 39, 42, 57, 62, 85, 97-98, 116, 125-126, 131-132, 135137, 140, 145-146, 148-149, 153, 155, 157, 166, 174, 189-190, 205, 210 method, 42, 85, 145, 153, 155, 189-190, 210 Tetraluoroethylene, 2, 4, 25-26, 76-77, 96, 184-185, 193, 208-209 Theory, 109, 114, 135 Thermal analysis, 46, 59-60, 66, 68, 71, 73, 86-87, 109, 132, 157, 174 Thermal conductivity, 23-24, 57, 64-67, 85, 145, 177, 189, 192, 197, 206 Thermal degradation, 80, 82, 193, 202 Thermal diffusivity measurements, 67 Thermal history, 196, 202 Thermal properties, 4, 17, 19, 24, 33, 35, 37-38, 40, 53-55, 57, 59, 61, 63-67, 69, 71, 73, 75, 77, 79-81, 83, 85, 87, 89, 103-104, 106, 126, 132, 142, 161, 175, 197, 202, 207 Thermal resistance, 189, 210 Thermal stability, 4, 33, 36, 40, 63, 80, 89, 163, 168 Thermogravimetric analysis, 33, 39, 68, 77, 79-82, 112, 146 Thermogravimetric decomposition kinetics, 146 Thermogravimetry, 77, 81-82 - mass spectrometry, 81, 83 Thermo-mechanical analysis, 18, 57, 59-61, 63, 68-71 Thermo-oxidation, 20 Thermoplastic(s), 8, 16-17, 19, 34, 39, 55, 73, 88, 119, 161, 163, 166-168, 171, 184, 188, 190, 195, 200 elastomer, 166, 184, 188 olein, 161, 167-169, 171 polymers, 34, 190 Thermoset, 34 Thermosetting, 84, 190-191

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Engineering Plastics Thickness, 15, 67, 93, 108, 135, 137, 144-145, 167, 174, 198, 203-204 Three-dimensional, 132 Time, 14-15, 21-22, 35, 39, 57, 59, 64-65, 69, 73, 77, 97-98, 126, 142-152, 165, 167-168, 174, 176, 179, 189-190, 194, 196, 198, 200-205 -temperature superposition, 35, 190 Tip(s), 33, 135, 167, 177 Tool, 5, 20, 132, 167 Toughness, 10-13, 19-20, 23, 34, 40, 115, 177, 187-188, 190, 194 Toxic, 115 Tracking resistance, 3, 13, 98-99, 104-105, 109 Transfer, 58, 67, 73, 174 moulding, 174 Transient plane source technique, 65-66 Transition, 18, 23, 33, 61, 67-70, 72, 74, 109, 140, 176-177 Transmission, 3, 25, 32, 39, 85, 134, 189 electron microscopy, 39, 134 Transparency, 80, 134, 202 Transportation, 166, 169, 178 Trapping, 40, 115 Triethylenetetramine, 41 Tyres, 169

U Ultimate tensile strength, 191 Ultra-high molecular weight polyethylene, 14, 126, 139, 162, 183-184, 186, 188, 195 Ultrasonic, 16, 34, 146 spectroscopy, 146 Ultraviolet, 10-13, 112, 135-136, 162, 186, 206, 208-209 Underwriters Laboratories, 61, 190, 210 Unilled, 36, 40, 65, 126, 164, 187 Unsaturated, 16, 163 Unstable, 111 Urea-formaldehyde, 1, 95, 99, 101, 139, 208-209

V Vacuum, 98, 199 Validation, 201 Vapour, 36, 64, 144, 175, 192, 202, 205-206 grown carbon-ibre, 64-65, 175

262

Index Velocity, 16, 36, 132 Vibration, 20, 73, 164, 166, 179 VICAT Method, 59 Viscosity, 19, 33, 57, 104, 106-107, 164, 168 Vitriication, 16 Voice coil motors, 65 Volatile, 77, 174 content, 174 Voltage, 73, 93, 97-98, 107, 194 Volume, 3, 13, 35, 43, 51-52, 59, 69, 84, 87, 94, 97-99, 103-105, 107-108, 113, 126, 152-153, 155, 169, 171, 197 resistivity, 3, 94, 97, 99, 103-105, 107-108, 113 Volumetric, 16, 57, 66, 69 Vulcanisation, 167

W Washing, 3, 187 Water, 5, 12, 14, 23, 25, 62, 77, 105, 108, 110, 113, 126, 138, 140-142, 144, 155, 174, 192, 202, 204-206 activity, 142-143, 204, 206 vapour, 144, 192, 202, 206 Weatherability, 162 Weathering tests, 135 Weibull distribution function, 131 Weight, 2, 4, 14, 17-20, 37-40, 57-58, 60-61, 76-77, 79-81, 96, 101, 104, 108, 113, 126, 133, 136, 140-142, 145-146, 161-162, 164, 175-177, 179, 186, 192, 195-196, 204, 207 average molecular weight, 18 fraction, 38-39, 108 loss, 18-19, 40, 61, 76-77, 79-80, 146, 204 ratio, 175, 179 Weld line strength, 36 Welding, 19-20 White crazes, 134 Wind, 25, 35 Window, 162, 165, 199

X X-ray diffraction, 36, 143, 202

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Engineering Plastics

Y Yield, 7, 9-10, 12-13, 36, 38-39, 79, 100, 165, 174, 194 point, 9, 13 Yielding, 197 Young’s modulus, 23, 33-34, 36, 39-40, 68

Z Zinc oxide, 109

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Published by Smithers Rapra Technology Ltd, 2014

Generally speaking, engineering plastics are those which are replacing conventional materials such as metals and alloys in general engineering. In addition, the term ‘engineering plastic’ covers materials that have superior properties which were not particularly available in conventional polymeric materials such as the exceptionally high heat resistance of polyimides and polysulfides. In addition to conventional materials engineering polymers include materials as diverse as polyether ether ketone, polyimide, polyetherimide and polysulfides and polysulfides. Engineering polymers can be reinforced by the inclusion in their formulations of glass fibres, carbon fibres and nanotubes which produce appreciable improvements in mechanical and thermal properties. The book aims to provide a complete coverage of the types of plastics which are now increasingly being used in engineering in applications as diverse as gears, aircraft body construction, micro-electronics and extreme high temperature applications, steel replacement and artificial hip joints. The book also intends to provide a complete review of the use of polymers in engineering. The mechanical, electrical and thermal properties of polymers are discussed as are other diverse applications such as solvent and detergent resistance, frictional and hardness properties, food packaging applications and gas barrier properties. In addition a very important application is discussed of the resistance of plastics to gamma and other forms of radiation namely their use in nuclear industry, medical applications and food sterilisation. The book will be of interest to those at all levels who are concerned with general engineering, building, automotive, aerospace, electronics, mechanical and nuclear industries. It will also be of interest as a source book to materials scientists, those concerned with the development of new materials and students of engineering and related studies.

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