CRYSTALLIZATION OF POLY(BUTYLENE TEREPHTHALATE) AND ITS BLENDS WITH POLYARYLATE

In this paper we explore the crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and miscible blends of PBT with a polyarylate based on Bisphenol A and a 75/25 mole ratio of isophthalic and terephthalic acids. For PBT, a regime II --> III transition is indicated near 210-degrees-C (DELTA-T approximately 30-degrees-C) and the fold surface free energy (sigma(e)) was found to be in the range of 57-75 erg/cm2. This leads to a work of chain folding (q) of approximately 3-5 kcal/mol folds. Analysis of the crystallization data of van Antwerpen and van Krevelen for PET shows that crystallization occurs in regime II across a wide range of T(c). Sigma(e) was estimated to be approximately 140 erg/cm2 and q approximately 10 kcal/mol from their data. These values are roughly twice that of PBT, consistent with the longer flexible segments in the PBT repeat unit. Crystallization data for three PBT/PAr blends was analyzed using a modified Lauritzen-Hoffman method and compared to that of pure PBT.