Effect of molecular architecture of in situ reactive compatibilizer on the morphology and interfacial activity of an immiscible polyolefin/polystyrene blend

Abstract

Two different types of in situ compatibilizers, poly(ethylene-ran-acrylic acid) (PE-r-AA) and poly(propylene-graft-acrylic acid) (PP-g-AA), are added to the polystyrene/poly(styrene-ran-glycidyl methacrylate) (PS-GMA) system to study the effect of the distribution of functional units across the entire polymer chain (molecular architecture) of an in situ compatibilizer on the morphology and the reduction in domain size of the disperse phase. The acrylic acid group in both PE-r-AA and PP-g-AA is known to react very easily with the epoxy group in PS-GMA, and thus the PE (or PP)-graft-PS copolymer is formed. We have shown that a random-type copolymer of PE-I-AA is a very effective compatibilizer, in that the domain size of the disperse phase in the PE-r-AA/PS/PS-GMA blend was significantly reduced when increasing the amount of PS-GMA. However, a graft-type copolymer of PP-g-AA is not an effective compatibilizer to reduce domain size of the disperse phase in PP-g-AA/PS/PS-GMA blend even when PS-GMA is added up to 9 wt%. This result is explained by the existence of an inhomogeneous distribution of functional units of AA in PP-g-AA and the homopolymer poly(acrylic acid) (PAA), while for PE-r-AA functional units of AA are well distributed across the entire chain, and no homopolymer of PAA exists. The existence of an inhomogenous distribution of functional units in PP-g-AA was studied by dynamic mechanical thermal analysis and by scanning electron microscopy or transmission electron microscopy. (C) 1997 Elsevier Science Ltd.