Estimation of the service lifetime of cable sheath materials designed for working in harsh operating environment

Paper deals with estimation of the service lifetime of two polymeric compounds used for cable sheath manufacturing. Both tested compounds are designed for working in harsh operating environment at increased temperature (≥60 °C). While the first material, used as a reference material in our study, has planning service lifetime of 40 years and is already being used, the second material is a new candidate material with improved lifetime (>60 years). Service lifetime was estimated using accelerated thermal aging and application of Arrhenius law. The activation energy together with an estimation of the temperature of accelerated aging was determined by differential scanning calorimetry. Obtained values helped with calculation of the times of accelerated thermal aging for the both tested compounds. Thermal aging was carried out according to ČSN EN 60216-1 while elongation at break was measured at every stage of the aging. Reduction of elongation at break to 50 % of its original value was considered as an end-point criterion. The results point to an unusual stability of the tested compounds. Results also well demonstrate the differences between reference and candidate compound in terms of their absolute values of elongation at break.