STRUCTURE-PROPERTY RELATIONSHIPS IN A REACTIVELY COUPLED DUCTILE MATRIX BRITTLE DISPERSED PHASE BLEND

Blends of t-butylaminoethyl methacrylate grafted polyethylene (PE-g-tB AEMA) with methyl methacrylate-methacrylic acid copolymer (PMMA-MAA) a nd polymethyl methacrylate (PMMA) were prepared in a Banbury type batc h mixer. The effects of component proportions and processing condition s on the melt flow index, morphology, impact, and tensile properties o f the resulting polymer blends were investigated. The interfacial chem ical reaction was studied using Fourier transform infrared (FTIR) tech nique. It was observed that the melt index of the blends was reduced w ith increasing melt processing temperature and mixing time, indicating the formation of PE-g-PMMA block copolymer. New IR bands at 1554, 162 8, 1800, and 1019 cm-1 were observed only for PE-g-tBAEMA/ PMMA-MAA, t he reactive blends, but not for PE-g-tBAEMA/PMMA, the nonreactive blen ds. 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 com positions was examined using scanning electron microscopy (SEM) and re lated 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 correspondin g nonreactive blends. For the reactive polymer blends consisting of br ittle particles dispersed in the ductile matrices, the PE-g-tBAEMA/PMM A-MAA, impact and tensile results higher than predicted by the additiv ity rule were observed. The toughening of polyethylene by PMMA was exp lained by a ''cold-drawing'' mechanism. The Young's modulus of the ble nds and the extent of interfacial adhesion were analyzed with Takayana gi and Sato-Furukawa's theories. (C) 1993 John Wiley & Sons, Inc.