The most important member of the Thermoplastic Polyester family is polyethylene terephthalate (PET). It was invented in the early 1940s in Manchester by Whitfield and Dickson. This is a good example of how inventions tend to emanate from smaller organisations, in this case Calico Printers Association. It was left to big organisations, ICI and DuPont, to develop the material commercially. (My closest brush with fame was back in the 1960s when I inherited Jim Dickson’s desk when I changed companies.)
The initial attraction of PET was as a fibre (‘Terylene’, ‘Dacron’). However. it quickly became popular as a transparent packaging film (‘Melinex’, ‘Mylar’). Eventually it has become the material of choice for bottles.
Early on, injection moulding machines could not cope very well with PET’s high melt transition temperature (265oC). Today that is less of a problem. To fill the gap, polybutylene terephthalate (PBT) was introduced as a moulding material, with a slightly lower Tm (230oC) and a lower melt viscosity, while still retaining much of the good mechanical, chemical, electrical and thermal properties of PET. Today PBT, particularly its glass filled grades, finds many applications in electrical equipment. These applications include connectors, sockets, bobbins, motor housings and insulation.
PET Trade names: Arnite, Impet, Ramapet, Rynite, Valox, Skygreen, Tripet
PBT Trade names: Arnite, Celanex, Crastin, Lupox, Luranyl, Pocan, Ultradur, Valox
In terms of properties, PBT is now featuring in blends with PET and also with polycarbonate, ABS and ASA.
This Thermoplastic Polyester article was written by Dr. Charlie Geddes for Hardie Polymers
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