MISCIBLE BLENDS OF POLY(BUTYLENE TEREPHTHALATE) AND THE POLYHYDROXYETHER OF BISPHENOL-A

Melt blends of poly(butylene terephthalate) (PBT) and the polyhydroxyether of bisphenol A (phenoxy) exhibit excellent transparency above the melting point of PBT as well as for the quenched molded specimens. Dynamic mechanical and calorimetric characterization revealed single and sharp glass transitions intermediate between those for the individual constituents. Increasing phenoxy content in the blends depressed the crystallization rate of PBT due to dilution and viscosity (Tg increase) effects. The apparent miscibility is believed due to the potential specific interactions between phenoxy pendant hydroxyl (proton donor) and the ester carbonyl of PBT (proton acceptor). Heat of fusion results surprisingly show an increase in the degree of PBT crystallinity as the phenoxy content of the blend is increased. No explanation is offered at this point for this unexpected behavior. Copyright © 1979 John Wiley & Sons, Inc.