Polyethylene terephthalate moulding materials

Glass-filled, toughened polyethylene terephthalate) (PET) resins can be readily moulded into highly impact-resistant structural parts for appliances and automotive components. The PET-based compounds are also suitable for construction (e.g. as structural members), equipment housings (e.g. printer and copier parts), agricultural applications (e.g. mower and tractor engine covers), materials handling (e.g. pallets and trays), furniture (e.g. office chair bases), as well as electrical and electronic applications. 

By far the most important plastic is polyethylene terephthalate (PET). Bottles of this material are formed in a two-stage process. So-called pre-forms are made by injection moulding and, in a second process, are then stretch-blow-moulded to produce a bottle. PET has properties surprisingly like those of glass, but it does not have the same disadvantages of weight and brittleness. 

Polyester polymers are materials which exhibit various chemistries but all contain ester linkages in the polymer chain. They have attained industrial importance as moulded materials, fibres, packaging film and as structural materials which are reinforced with fibres and fillers. Chemists, John Rex Whinfield and James Tennant Dickson, employees of the Calico Printer s Association of Manchester, patented polyethylene terephthalate in 1941, after advancing the early research of Wallace Carothers. Poly (ethylene terephthalate) is the basis of polyester fibres and fizzy drinks botdes. The first polyester fibre known as Terylene was also developed in 1941. 

Polyethylene terephthalate (PET) (Scheme 5.1) is a linear thermoplastic polyester with excellent mechanical, chemical and physical properties, and optical clarity, which is widely used in multiple applications such as food packaging, soft-drink bottles, photographic films, audio tapes, video tapes, fibres and fihn-moulding materials. Currently, the overall world consumption of PET amounts to about 13 million tonnes. In view of such a large consumption, the effective utilisation of PET waste is of considerable commercial and technological significance. 

Substantial quantities of UPVC are also used for blow moulded containers for such diverse materials as consumable liquids such as fruit squashes, liquids for household use such as detergents and disinfectants, cosmetics and toiletries, and pharmaceuticals. For most of these applications UPVC is in competition with at least one other polymer, particularly poly(ethylene) terephthalate (Chapter 25), polyethylene (Chapter 10), polypropylene (Chapter 11) and, to a small extent, the nitrile resins (Chapter 15). The net result is that in recent years there has been some replacement of PPVC in these areas, in part because of problems of waste disposal. 

The decorative laminates described in the previous chapter are made with selected thermosetting resins while resins of this type can be moulded and extruded by methods similar to those outlined in the present and the next chapter the materials employed for these processes predominantly are thermoplastic. Many such plastics can be moulded and extruded under suitable conditions, the most important in terms of quantities used being those that combine properties satisfactory for the purpose with convenience in pro-cessing-especially the polyolefins (polyethylene and polypropylene), poly(vinyl chloride), and styrene polymers and blends. Other plastics with special qualities, such as better resistance to chemical attack, heat, impact, and wear, also are used—including acetals (polyformaldehyde or polyoxymethylene), polyamides, polycarbonates, thermoplastic polyesters like poly(ethylene terephtha-late) and poly(butylene terephthalate), and modified poly(phenylene oxide),... 

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