Compatibilization of PBT/polyolefin blends: Mechanical and dynamic mechanical properties

Blends of polybutylene terephthalate (PBT) with very low-density polyethyle ne (VLDPE) have been studied. The blends are immiscible owing to the differ ences in the polarities of the component polymers. Thermal studies using a differential scanning calorimeter showed that the blending does not change the crystallinity and non-isothermal crystallization behavior of PET. The t ensile strength and modulus showed gradual decrease with increase in VLDPE content. The impact strength, however, was found to increase marginally wit h increasing VLDPE content. The examination of fractured surfaces using sca nning electron microscopy indicated a two-phase morphology with spherical d omains of VLDPE dispersed in PET matrix. Addition of ethylene-based compati bilizers resulted in significant improvements in the mechanical properties through modification of phase morphology and interfacial adhesion. The effe ctiveness of the compatibilizers has been explained on the basis of possibl e interaction between the reactive groups present in the compatibilizer and the polymer. The presence of such bonding reaction leading to better inter facial properties has also been confirmed using lap shear measurements. (C) 2000 John Wiley & Sons, Inc.