SATURATED POLYESTERS PET, PBT

Saturated Polyesters (PET, PBT) The most prominent polymer in this family is polyethylene-terephthalate (PET), developed in 1945 as a condensation product between terephthalic acid and glycol. This linear polyester is used as a fiber (Terylene or Dacron ) or a film (Mylar ), but its main utility lies in the domain of bottles for soft drinks. Polybutylene-terephthalate (PBT) has also been introduced as an engineering material in addition to textiles. [Pg.171]

PET is produced from teraphthalic acid and ethylene glycol, while PBT is made with butylene diol. The diacid is obtained by catalytic oxidation of para-xylene (a by-product of the petrochemical industry) while ethylene glycol is obtained from ethylene oxide (an oxidized derivative of ethylene).The terephthallic acid is preferably replaced by the ester dimethyl-terephthalate [Pg.171]

Tm = 265°C and Tg = 80 C. It is more rigid and stable than Nylon, but inferior in tensile strength and toughness. The average molecular weight (number average) is around 20,000. [Pg.171]

The unsaturated polyesters (mainly used for coatings, including alkyds) are probably better known. However this type of polyester will be discussed later together with other thermosetting polymers. [Pg.172]

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