Structure‐property relationships in a reactively coupled ductile matrix/brittle dispersed phase blend

Abstract

AbstractBlends of t‐butylaminoethyl methacrylate grafted polyethylene (PE‐g‐tBAEMA) with methyl methacrylate‐methacrylic acid copolymer (PMMA‐MAA) and polymethyl methacrylate (PMMA) were prepared in a Banbury type batch mixer. The effects of component proportions and processing conditions on the melt flow index, morphology, impact, and tensile properties of the resulting polymer blends were investigated. The interfacial chemical reaction was studied using Fourier transform infrared (FTIR) technique. It was observed that the melt index of the blends was reduced with increasing melt processing temperature and mixing time, indicating the formation of PE‐g‐PMMA block copolymer. New IR bands at 1554, 1628, 1800, and 1019 cm−1 were observed only for PE‐g‐tBAEMA/PMMA‐MAA, the reactive blends, but not for PE‐g‐tBAEMA/PMMA, the nonreactive blend. These IR bands were attributed to the amide, carboxylate anion and methacrylimide formation resulting from the chemical reaction between the secondary amine on the PE‐g‐tBAEMA/PMMA moiety and the carboxylic acid on PMMA‐MAA segment. The morphology of the blends in various compositions was examined using scanning electron microscopy (SEM) and related to their mechanical properties. All of the blends have a domain structure whose morphology is strongly dependent on the concentration of the dispersed phase. Furthermore, the PE‐g‐tBAEMA/PMMA‐MAA reactive blends were shown to have much finer morphology than the corresponding nonreactive blends. For the reactive polymer blends consisting of brittle particles dispersed in the ductile matrices, the PE‐g‐tBAEMA/PMMA‐MAA, impact and tensile result higher than predicted by the additivity rule were observed. The toughening of polyethylene by PMMA was explained by a “cold‐drawing” mechanism. The Young's modulus of the blends and the extent of interfacial adhesion were analyzed with Takayanagi and Sato‐Furukawa's theories. © 1993 John Wiley & Sons, Inc.