Properties of uncompatibilized and compatibilized poly(butylene terephthalate) LLDPE blends

In this work, blends of poly(butylene terephthalate) (PBT) and linear low-d ensity polyethylene (LLDPE) were prepared. LLDPE was used as an impact modi fier. Since the system was found to be incompatible, compatibilization was sought for by the addition of the following two types of functionalized pol yethylene: ethylene vinylacetate copolymer (EVA) and maleic anhydride-graft ed EVA copolymer (EVA-g-MAH). The effects of the compatibilizers on the rhe ological and mechanical properties of the blends have been also quantitativ ely investigated. The impact strength of the PBT-LLDPE binary blends slight ly increased at a lower concentration of LLDPE but increased remarkably abo ve a concentration of 60 wt % of LLDPE. The morphology of the blends showed that the LLDPE particles had dispersed in the PET matrix below 40 wt % of LLDPE, while, at 60 wt % of LLDPE, a co-continuous morphology was obtained, which could explain the increase of the impact strength of the blend. Gene rally, the mechanical strength was decreased by adding LLDPE to PET. Additi on of EVA or EVA-g-MAH as a compatibilizer to PBT-LLDPE (70/30) blend consi derably improved the impact strength of the blend without significantly sac rificing the tensile and the flexural strength. More improvement in those m echanical properties was observed in the case of the EVA-g-MAH system than for the EVA system. A larger viscosity increase was also observed in the ca se of the EVA-g-MAH than EVA. This may be due to interaction of the EVA-g-M AH with PET. (C) 1999 John Wiley & Sons, Inc.