Influence of Chain Structure on Phase Behavior and Thermal Degradation of Poly(trimethylene terephthalate)/Poly(hydroxy ether) of Bisphenol-A Blends

This paper describes thermal decomposition and phase behavior of binary blends composed of poly(trimethylene terephthalate), (PTT), and a phenoxy resin namely poly(hydroxy ether) of bisphenol-A prepared via melt blending. Analysis of the SEM and DMA results revealed that except for PTT/phenoxy 90/10 sample, all PTT/phenoxy blends were homogeneous. The reactions occurring in PTT/phenoxy system and their effect on molecular weight were investigated by 1 H NMR and GPC respectively. 1 H NMR spectra proved that the reaction of grafting PTT on phenoxy chains occurs in the system which eventually leads to formation of cross-linked structures in the system. It was also found that chain scission reactions are responsible for decreasing molecular weight at low temperatures, while at higher temperatures formation of cross-linked structures increases thermal stability of the blends. Investigation on type of atmosphere (nitrogen and oxygen) showed no significant effect on the thermal stability of the blends especially at low temperatures. However, oxygen results in formation of a high-temperature shoulder in the TGA curves. This shoulder is attributed to degradation of cross-linked structures formed during the TGA heating scan.