Effects of Aging on the Fracture Behavior of Chlorinated Polyethylene and Chlorosulfonated Polyethylene

Abstract

Abstract The thermoxidative aging behavior of chlorosulfonated polyethylene (CSM) and chlorinated polyethylene (CPE) vulcanizates has been investigated. Aging rates were determined by measuring isothermal oxidative induction times in a differential scanning calorimeter. Aging rates were also determined by measuring the decrease in the critical tearing energy of compounds as a function of aging time and temperature. Rate constants determined from induction time and tearing energy experiments displayed typical Arrhenius behavior. Below 240°C, rate constants from both experiments fell on the same line, suggesting that both experiments probe the same reaction. Activation energies for degradation of CSM and CPE were 88 and 108 kJ/mol respectively. Above 240°C, the mechanism of degradation changes with a corresponding change in activation energy to 190 and 232 kJ/mol for CSM and CPE, respectively. In the unaged state, the critical tearing energy of the carbon black-filled CPE compound is 50% higher than that of the carbon black-filled CSM compound. The rate of aging of CSM compound is approximately twice that of the CPE compound at equal temperatures. Decreases in tearing energy were attributed to additional crosslinking of the elastomer network. Combining oxidative induction times and critical tearing energy measurements may offer significant advantages in streamlining accelerated testing of elastomeric materials.