Mixed crosslinking in chlorosulfonated polyethylene and its blend with ethylene vinyl acetate copolymer

Chlorosulfonated polyethylene (CSM) reacts with aluminum oxide in the prese nce of stearic acid producing an ionic elastomer. Although CSM cannot be cr osslinked with dicumyl peroxide (DCP) alone, DCP crosslinking can be achiev ed in the presence of aluminum oxide and stearic acid. Moving die rheometri c (MDR) studies show the occurrence of a two-stage crosslinking. In the fir st stage, the loss component of the torque increases with an increase in th e storage component of the torque indicating the formation of ionic crossli nking, whereas in the second step the loss component of the torque decrease s along with an increase in the storage component of the torque. The second step indicates the formation of covalent crosslinking. Blends of aluminum salt of CSM and ethylene vinyl acetate copolymer (EVA) were prepared by int ensive mixing of the preformed masterbatches of EVA/DCP and CSM/aluminum ox ide/stearic acid. The formation of a technologically compatible blend is du e to the interaction between the aluminum sulfonate groups of CSM and the d ipole groups present in the EVA, which results in synergism in the tensile strength. Infrared spectroscopic studies reveal that the dipoles of EVA int eract with the ionic groups present in CSM.