Thermal behaviour and morphology of copolyterephthalates derived from trimethylene glycols

Abstract

AbstractThe thermal behaviour and the morphology of four polyterephthalate samples have been studied. Two of these samples are the pure homopolymers poly(trimethylene terephthalate) (PTMT) and poly(oxyditrimethylene terephthalate) (PTMTMT), while the other two are copolymers of both polyesters with 13 and 33% by weight of PTMTMT. It was found that the insertion of units of PTMTMT in the copolymers derived from PTMT produces a depression of the glass transition and melting temperatures as a consequence of the higher flexibility of the former units, and several equations have been tested to fit that depression. Moreover, the crystallization rate of PTMTMT was found to be very slow, and the need for higher supercoolings to crystallize the samples in a reasonable time, as the PTMTMT content increases, implies the formation of a greater number of nuclei, with subsequent inconvenience when trying to follow the evolution of the radii of the observed spherulites. On the other hand, well developed spherulites were obtained for the samples rich in PTMT, and two different kinds of this superstructure were observed, depending on the crystallization temperature.