Application of small punch test to lifetime prediction of plasticized polyvinyl chloride wire

In this study, it was investigated that the validity of small punch (SP) test for the lifetime prediction of polyvinyl chloride (PVC) resin used as an electric insulation material for the electric cable. The degradation behavior of PVC resin under the accelerated high-temperature condition was analyzed using Fourier transform-infrared spectroscopy (FT-IR), tensile testing, and SP testing. The activation energies and estimated lifetime obtained from the Arrhenius method were compared. The peak ratio of the carbonyl group obtained by FT-IR, the elastic modulus obtained by tensile testing, and the apparent elastic modulus obtained by SP testing were used as indicators for lifetime estimation, and the logarithm of these values showed a linear correlation with exposure time. The activation energy obtained from the apparent elastic modulus using SP testing was the smallest and the predicted lifetime was the shortest among all mechanical properties in this research. It indicates that SP testing is sensitive to the degradation. This is because the stress at the surface becomes maximum for SP testing, and the degradation occurs at the surface of the materials by priority degradation. SP testing is an excellent minimally destructive lifetime prediction method for detecting of early-stage degradation.