Compatibility and physical properties of a new polyester blend

The compatible nature of a new polyester blend, polybutylene‐terephthalate (PBT) and a copolyester of bisphenol‐A‐neopentyl glycol‐terephthalate (CP‐350), has been inferred from the single Tg by DSC and dynamic mechanical studies. Compatibility is further confirmed from the progressive melting point depression of PBT, and the increasingly coarse and open spherulitic morphology of the blends as the weight percent of CP‐350 increases. At and above 40 weight percent of CP‐350, crystallization of PBT is impeded by the presence of high concentrations of CP‐350 which results in a low degree of PBT crystallinity (0‐8 percent) in such blends. The melt viscosity as a function of blend composition shows a good fit to the Hayashida model.