ABSTRACT
Polyesters are polymers containing the recurring ester unit ~ COO ~. They are formed by a condensation reaction between carboxyl-and hydroxyl-containing compounds. Historically, the first polyesters were condensation products of glycerol and phthalic anhydride. Those resins were used in the paint industry as early as 1910, but they were of low molecular weight and brittle. Later on, that is by 1925, they were modified by the inclusion of monofunctional fatty acids, which compensated the third functional group of the glycerol and elastified the resins. If unsaturated fatty acids were used, they rendered the resulting resins cross-linked by air oxidation. All these resins are now generally referred to as “alkyd resins”; they are treated in Chapter 6
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