INFLUENCE OF FILLER-POLYMER INTERACTIONS ON THE CURE MISMATCH OF DISSIMILAR POLYMERIC BLENDS

Cure mismatch between the blends of two dissimilar polymers, poly [ et hylene(vinyl acetate)] (EVAc-28, VAc content 28%) and polychloroprene( CR) was investigated through rheometric, mechanical, and dynamic mech anical properties. These studies indicate cure-heterogeneity due to fa st curing as well as degradation of CR with dicumyl peroxide (DCP) at 170 degrees C, which facilitates easy liberation of acidic HCl. The lo w temperature curing of unfilled blends at 145 degrees C reduces the r ate of curing as well as liberation of HCl, leading to lower cure hete rogeneity and improved physical properties compared to those cured at 170 degrees C. The high specific component of surface energy of carbon black (N110) leads to better filler-polymer interaction with more pol ar CR and causes lowering in effective occluded volume measured from s torage modulus. Carbon black suppresses the cure heterogeneity of the blends and improves their physical properties considerably. CR, which shows higher minimum rheometric torque compared to EVAc-28, is more vi scous and hence carbon black incorporation is relatively difficult. Th is also leads to higher agglomerate structure causing higher networkin g factor. (C) 1997 John Wiley & Sons, Inc.