Long-term stress relaxation prediction for elastomers using the time–temperature superposition method

Increasingly, manufacturers need to provide warranties of over 10 years on rubber seals, gaskets and air-springs and warranties of between 20 and 30 years on O-rings for underground applications [Parker Hannifin Corp. Compression set vs. compression stress relaxation. vol. 1, No. 3; 2003.]. In order to expedite the development process, experimental concepts for accelerated forecasts of long-term relaxation are required. Previously the standard procedures have relied upon semi-quantitative methods which considered material behaviour at elevated temperatures. The objective of the work presented here is to develop precise forecasting procedures with the use of the time–temperature superposition principle, the Williams–Landel–Ferry (WLF) equation [J.D. Ferry. Viscoelastic properties of elastomers. 3rd ed.; 1980.] and the Arrhenius equation [ISO 11346. Rubber, vulcanised or thermoplastic – estimation of life-time and maximum temperature of use from an Arrhenius plot. 1997.].