Accelerated thermal ageing studies of polydimethylsiloxane (PDMS) rubber

Thermal ageing studies over relative high temperature range (from 250 degrees C to 85 degrees C) have been conducted on polydimethylsiloxane (PDMS) rubber with the aim of investigating ageing behavior. Tensile elongation, compression set and creep measurements are introduced to monitor the ageing process. Time temperature superposition is performed and the linear trends are found in the Arrhenius plots for all the approaches, revealing an identical process dominates the degradation process. Activation energies are found to be depended on the methods used, which are 88.5 kJ/mol for tensile tests, 67.7 kJ/mol for compression set measurements and 75.3 kJ/mol for creep measurements. The phenomenon that activation energy obtained from tensile elongation is always higher than other approaches is rationalized by the sensitive modification of thermal degradation on the rubbery network. Moreover, correlations between the results from different approaches have been examined. The linear relationships have been found between tensile elongation and creep or compression set measurements for the three methods are all influenced by the network structure.