Split dynamic mechanical relaxation of an inhomogeneous dielectric and the insights into its anomalous characteristics

Abstract

The split relaxations of an inhomogeneous polymer were investigated in this paper, with special attention paid to the application of classic dynamic mechanical analysis (DMA) to inhomogeneous dielectrics. The single relaxation peak of the pristine epoxy resin split to two peaks after thermal ageing, concerning its transition toward an inhomogeneous skin-core structure. Moreover, the relaxation corresponding to the skin-layer, which only took up a small proportion in volume, anomalously dominated the entire relaxation response. The core-layer’s response was even unidentifiable when its proportion was below 65 vol%. This was found strongly correlated with the non-uniform distribution of applied stress during DMA test which kinetically affected the viscoelastic response received from the specimen. Since potential misjudgment could be induced in this case, it should be a critical issue deserving more attention.