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

Chlorosulfonated polyethylene (CSM) reacts with aluminum oxide in the presence of stearic acid producing an ionic elastomer. Although CSM cannot be crosslinked with dicumyl peroxide (DCP) alone, DCP crosslinking can be achieved in the presence of aluminum oxide and stearic acid. Moving die rheometric (MDR) studies show the occurrence of a two-stage crosslinking. In the first stage, the loss component of the torque increases with an increase in the storage component of the torque indicating the formation of ionic crosslinking, whereas in the second step the loss component of the torque decreases 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 intensive mixing of the preformed masterbatches of EVA/DCP and CSM/aluminum oxide/stearic acid. The formation of a technologically compatible blend is due to the interaction between the aluminum sulfonate groups of CSM and the dipole groups present in the EVA, which results in synergism in the tensile strength. Infrared spectroscopic studies reveal that the dipoles of EVA interact with the ionic groups present in CSM.