Morphological Development and Crystallization Behavior of a Poly(trimethylene terephthalate)/ Poly(hydroxy ether of bisphenol A) Blend

摘要

It is well known that the morphology of crystalline polymer blends is highly influenced by the phase behavior in the molten state [1-6]. If the blend has a lower critical solution temperature (LCST) or upper critical solution temperature (UCST) phase diagram,crystallization may proceed simultaneously and compete with liquid-liquid (L-L) phase separation [2-3,7]. The two competitive processes may create unique morphological patterns that are not attainable by either process alone. Blends of poly(trimethylene terephthalate) (PTT) and poly(hydroxyl ether of bisphenol A) (phenoxy) are basically immiscible over a wide range of compositions. During melt processing,interchange reactions between the phenoxy hydroxyl and ester type carbonyl groups take place. These reactions lead to the formation of graft or cross-linked copolymers,enhancing the miscibility of the blends. With an increase in the reaction extent,the compatibility of the blends increases from complete incompatibility to partial compatibility and finally to complete compatibility. Therefore,PTT/phenoxy blends provide a unique opportunity for investigating the effects of various liquid-phase changes on crystalline morphology. In this work,we carried out time-resolved light scattering (TRLS) and optical microscopy (OM) observations to confirm L-L phase separation via spinodal decomposition (SD) in an extruded PTT/phenoxy blend and investigated the effects of L-L demixing and subsequent phase homogenization on crystallization. The characteristics of the melting behavior and the lamellar morphology were also examined on the basis on the effects of combined crystallization and L-L demixing..