Miscibility behaviors in poly(butylene terephthalate)/polyarylates based on bisphenol A copolymer blends

The miscibility and spherulitic growth rates of Poly(butylene terephthalate ) with Polyarylate based copolymer blends, PBT/PAr, were investigated using differential scanning calorimetry (DSC) and polarized optical microscopy ( POM). Five kinds of polyarylate copolymers based on Bisphenol A with differ ent molar ratios of isophthalic/terephthalic acids were prepared via. inter facial polymerization. The mean field theory of polymer/copolymer blend sys tem was introduced to explain the miscibility behaviors; this theory could predict miscibility in PBT/PAr blends qualitatively. It was found that the segmental interaction strength of PAr with PET followed the order of PAr(T- 100) > PAr(I-100) > PAr(I25-T75) > PAr(I75-T25) > PAr(I50-T50). The physica l origin of this phenomenon is very complex. One of possible reasons for th ese behaviors may arise from the conformations of PAr(T-100) and PAr(I-100) segments. The preferred conformation of PAr(T-100) was crank-shaft and the preferred conformation of PAr(I-100) was helix type. However, the conforma tion of PET in crystalline state was nearly linear. It was also shown that the segmental interaction strength of the blend influenced the spherulitic growth rate.