172.

Discuss the synthesis, properties and uses of polyesters.

Polyesters contain ester linkages. These are the condensation polymers of diacids and diols. Following are the two important polyester polymers:
(i) Dacron or Terylene : When ethylene glycol (ethane–1, 2–diol) is condensed with terephthalic acid (benzene-1, 4-dicarboxylic acid) at 423–473 K, terylene is obtained.

Terylene fibre is very much durable and crease-resistant. It has low moisture content and is not damaged by moths and mildew.

It is used for the manufacture of wash and wear fabrics and also blended with wool (terywool) and cotton (terycot) to increase their resistance to wear and tear. It is also used to prepare seat belt, sails and tyre cords.

(ii) Glyptal or Alkyd resin : The name glyptal refers to all polymers which are synthesised by the condensation of dibasic acids or their anhydrides and polyhydric alcohols like glycerol or glycol.

The simplest glyptal is synthesized d by the condensation of ethylene glycol and phthalic acid.


Poly (ethylene phthalate) is an example of a thermoplastic polymer. It is used in making building materials like asbestos and cement and in making adherent paints.