On the temperature dependence of the cyclic compression behaviour of a thermoplastic vulcanizate elastomer

Abstract

Effects of temperature on the uniaxial cyclic compression of a polypropylene based thermoplastic vulcanizate were studied in the range −40 °C–100 °C. The effect of temperature on the stress level was similar to that on the storage modulus from dynamic mechanical analysis. The residual strain after a cycle increased with decreasing temperature below 23 °C, while from 23 °C to 100 °C the effect of temperature was small. Both dependencies were correlated with the effect of temperature on the fraction of stress relaxed in the cycle. The residual strain after a cycle and the standard compression set (ISO 815–1, method A) had different temperature dependencies, and this was rationalized based on the different timescales of the tests and the different temperatures during loading and unloading. Two different methods for determining the Poisson's ratio in this temperature range were investigated in terms of measurement accuracy. The preferred method was based on input from dynamic mechanical analysis and triaxial compression.

Keywords

• Mullins effect
• Compression set
• Hysteresis loss
• Thermoplastic elastomer
• Bulk modulus
• Poisson's ratio