Temperature dependence of crystalline structure and DC performance in LLDPE/HDPE blending material

Abstract

Thermoplastic blending material is considered as a recyclable environmental-friendly potential candidate for future direct current (DC) cable insulation. Although such a non-crosslinking material has been proved to be superior in certain properties compared with cross-linked polyethylene (XLPE), one of the central concerns for the application of this material system lies in its DC performance at high temperature. In this paper, we investigate the DC conductivity and breakdown strength of a thermoplastic linear low-density polyethylene (LLDPE)/high-density polyethylene (HDPE) blending material under temperature range from 30 to 90°C, the results show that this blend exhibits better temperature-stability in DC performance, and it shows lower conductivity and higher breakdown strength compared with XLPE. The crystalline structure is studied through X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that the LLDPE/HDPE blend exhibits a co-crystalline structure with higher crystallinity and larger microcrystal, and when temperature rising, crystallinity and microcrystal size of blend decreases slower compared with XLPE. Such results might enable further application of the LLDPE/HDPE blend on DC cable insulation.