Polyethylene terephthalate (PET)

The material. The name polyester derives from a combination of Polymerization and esterification. Saturated polyesters are thermoplastic; examples are PET and PBT, which have good mechanical properties to tem­peratures as high as 175°C. PET is crystal clear and impervious to water and CO2, but a little oxygen does get through. It is tough, strong, and easy to shape, join, and sterilize, allowing reuse. Unsaturated polyesters are thermosets; they are used as the matrix material in glass fiber/polyester composites.

Composition

(CO-(C6H4)-CO-O-(CH2)2-O)n

General properties

Density

1290

– 1400

kg/m3

Price

*1.63

– 1.79

USD/kg

Mechanical properties

Young’s modulus

2.76

– 4.14

GPa

Yield strength (elastic limit)

56.5

– 62.3

MPa

Tensile strength

48.3

– 72.4

MPa

Compressive strength

62.2

– 68.5

MPa

Elongation

30

– 300

%

Hardness—Vickers

17

– 18.7

HV

Fatigue strength at 107 cycles

*19.3

– 29

MPa

Fracture toughness

4.5

– 5.5

MPa. m1/2

Thermal properties

Melting point

212

– 265

°C

Glass temperature

67.9

– 79.9

°C

Maximum service temperature

66.9

– 86.9

°C

Thermal conductor or insulator?

Good insulator

Thermal conductivity

0.138

– 0.151

W/m. K

Specific heat capacity

*1420

– 1470

J/kg. K

Thermal expansion coefficient

115

– 119

p, strain/°C

Electrical properties

Electrical conductor or insulator?

Good insulator

Electrical resistivity

3.3 X 1020 –

3.0 X 1021 pohm. cm

Dielectric constant

3.5 –

3.7

Dissipation factor

*0.003 –

0.007

Dielectric strength

16.5 –

21.7 106 V/m

PET drinks containers, pressurized and unpressurized.

Ecoproperties: material

Annual world production

9 X 106

– 9.2 X 106

tonne/yr

Reserves

*2.5 X 108

– 2.6 X 108

tonne

Embodied energy, primary production

79.6

– 88

MJ/kg

CO2 footprint, primary production

2.21

– 2.45

kg/kg

Water usage

*14.7

– 44.2

l/kg

Eco-indicator

360

– 400

millipoints/kg

Ecoproperties: processing

Polymer molding energy

*9.36

– 10.3

MJ/kg

Polymer molding CO2

*0.749

– 0.826

kg/kg

Polymer extrusion energy

*3.63

– 4

MJ/kg

Polymer extrusion CO2

*0.29

– 0.32

kg/kg

Recycling

Embodied energy, recycling

33.4

– 37

MJ/kg

CO2 footprint, recycling

0.928

– 1.03

kg/kg

Recycle fraction in current supply Recycle mark

20

A,

PET

– 22

%

Typical uses. Electrical fittings and connectors; blow molded bottles; pack­aging film; film; photographic and X-ray film; audio/visual tapes; industrial strapping; capacitor film; drawing office transparencies; fibers. Decorative film, metallized balloons, photography tape, videotape, carbonated drink containers, ovenproof cookware, windsurfing sails, credit cards.