Polyesters are polymers obtained by reacting monomeric
polycarboxylic acid and poly alcohols. They are practically free of fatty
acids (oils) and have a much simpler structure than that of alkyd.
Polyester resins do not undergo oxidative polymerization (curing) and
have a different curing mechanism than an alkyd.
Saturated polyesters are produced from a large number of polyfunctional
alcohols, for example, 1-6-hexanediol, neopentyl glycol, and polycarboxylic
acids (phthalic acid and adipic acid). Most saturated polyester
resins have relatively low molecular weights, ranging from 5000 to
10,000 g/mol. These resins do not have the mechanisms for curing, and
therefore, coatings prepared from them use cross-linking resins such as
melamine-formaldehyde (MF) resin, benzoguanimine-formaldehyde (BF)
resin, or epoxy resin.
