Methodologies for lifetime predictions of rubber using Arrhenius and WLF models

The WLF approach is appropriate for lifetime predictions when polymer agein g is controlled by a viscoelastic process (relaxation, creep). This methodo logy using time/temperature shift will be illustrated by the creep of SBR/N R. When physico-chemical mechanisms are dominant, the Arrhenius approach is th e most widely used for evaluating accelerated test results involving the ef fect of temperature. Service lifetimes have been estimated for the thermal ageing of NBR/PVC and for the ageing of HNBR in gaseous fluids. Predictions using the Arrhenius model usually do not take into account oxyg en-diffusion-controlled oxidations. In the case of the thermal ageing of EP DM, extrapolations are determined by the heterogeneity of the oxidative age ing of bulk polymer samples.