Polyethylene terephtalate

For the animals, see Pet.

Polyethylene terephthalate (aka PET, PETE or the obsolete PETP or PET-P) is a thermoplastic polymer resin of the polyester family. The chemical industry makes it. It is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination with glass fiber. It is one of the most important raw materials used in man-made fibers. It is also used as the dielectric in multi-purpose capacitors (K73-16 series).

PET
Density	1370 kg/m3
Young modulus(E)	2800–3100 MPa
Tensile strength(σt)	55–75 MPa
Elongation @ break	50–150%
notch test	3.6 kJ/m2
Glass temperature	75 °C
melting point	260 °C
Vicat B	170 °C
Thermal conductivity	0.24 W/m.K
linear expansion coefficient (α)	7×10−5/K
Specific heat (c)	1.0 kJ/kg.K
Water absorption (ASTM)	0.16
Price	0.5–1.25 €/kg
source: A.K. van der Vegt & L.E. Govaert, Polymeren, van keten tot kunstof, ISBN 90-407-2388-5

Depending on its processing and thermal history, it may exist both as an amorphous (transparent) and as a semi-crystalline (opaque and white) material. Its monomer can be synthesized by the esterification reaction between terephthalic acid and ethylene glycol with water as a byproduct or the transesterification reaction between ethylene glycol and dimethyl terephthalate with methanol as a byproduct. Polymerization is through a polycondensation reaction of the monomers (done immediately after esterification/transesterification) with ethylene glycol as the byproduct (the ethylene glycol is recycled in production).

The majority of the world's PET production is for man-made fibers (in excess of 60%) with bottle-making accounting for around 30% of global demand. In discussing cloth uses, PET is generally referred to as simply "polyester" while "PET" is used most often to refer to packaging applications.

Chemical structure of polyethylene terephthalate

• 
  A PET bottle (containing mineral water)
• 
  sails are often made of PET-fibers.