Polyester copolymers were prepared by polycondensation of pairs of the following diacids with ethylene glycol: Terephthalic acid, sebacic acid, 1, 2-diphenoxyethane-
p,
p′-dicarboxylic acid (B), 1, 2-di (
o-methylphenoxy) ethane-
p,
p′-dicarboxylic acid (M), and 1, 2-di (
o-methoxyphenoxy) ethane-
p,
p′-dicarboxylic acid (V). The copolymers obtained and their hot-pressed films were subjected to following measurements; melting point, crystal spacing, density, crystallinity by X-ray method, glass-transition (
Tg) and cold crystallization temperatures (
Tcc) by DTA method, and dynamic viscoelasticity.
From their melting points and crystal spacings, B-M, M-B and V-B copolymers are supposed to be isomorphous. Effects of isomorphism are observed in the following phenomena; smaller decrease in density and crystallinity, smaller increase in (
Tcc-
Tg), smaller decrease in half width and peak temperature of mechanical primary dispersion, smaller increase in dynamic modulus at 50°C, and smaller decrease in dynamic modulus at 120°C. Some discussion was made on these results.
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