The Enhanced Physical Properties of XLPE Insulation for High Voltage Cable Based on LDPE/LLDPE or LDPE/HDPE Blends

•High-temperature mechanical properties of XLPE cable insulation can be improved by blending LLDPE or HDPE.•The required blending content is very low (just 1 or 2 phr) and it can ensure stable electrical properties.•Polyolefin addition increases physical entanglement, which means a decrease in demand for DCP and is beneficial for cable insulation. Exploring methods of improving the performance of high-voltage cable XLPE insulation is a hot issue in high-voltage and insulation technology. This paper presented a new method to improve the physical properties of XLPE by doping low-content polyolefin materials, such as LLDPE or HDPE. The new XLPE insulation has significantly improved high-temperature mechanical properties and slightly improved room-temperature mechanical properties. The optimal thermal elongation properties were achieved with a 1 phr content of HDPE and LLDPE, while DC conductivity, DC breakdown strength, and dielectric properties were stable or slightly improved. The properties mentioned above showed a decreasing trend at higher content. This study demonstrated that adding HDPE or LLDPE to LDPE increases the physical entanglement of XLPE molecular chains, which has a similar effect to crosslinks formed by chemical crosslinking in enhancing the mechanical properties of XLPE insulation. This suggests that there is a potential to reduce the concentration of crosslinking agents during XLPE cable manufacturing while maintaining electrical properties and improving mechanical properties at elevated temperatures. It provides a new idea for improving the properties of XLPE insulation for high-voltage DC cables.