COCRYSTALLIZATION BEHAVIOR AND MELTING-POINT DEPRESSION IN POLY(ETHYLENE TEREPHTHALATE-CO-1,4-CYCLOHEXYLENE DIMETHYLENE TEREPHTHALATE) RANDOM COPOLYESTERS

The crystallization behaviour of the poly(ethylene terephthalate-co-1, 4-cyclohexylene dimethylene terephthalate) (P(ET/CT)) random copolyest ers is studied by d.s.c. analysis. ET units can crystallize with compl ete rejection of the CT units from the crystals, whereas CT units can co-crystallize with incorporation of ET units to some extent, resultin g in a minimum melting temperature at an intermediate composition of a bout 30-40 mol% CT. A good linear relation is found between the compos itions at which the melting point exhibits a minimum experimentally in various random copolyesters and those at which the cohesive energies for two components estimated by group contribution methods are identic al.