Study on the Performance Optimization of Recycled XLPE/HDPE Composites Based on Liquid Nitrogen Grinding Method

Recycling cross-linked polyethylene (XLPE) waste has become increasingly urgent due to severe environmental concerns and resource reuse challenges. This study presents an innovative liquid nitrogen cryogenic grinding method to effectively break the cross-linked structure of XLPE waste without thermal degradation. The effects of XLPE particle size, filler content, and the addition of maleic anhydride grafted polyethylene (MA-g-PE) compatibilizer on composite properties are systematically explored. Results indicate optimal composite performance at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5 \text{wt} \%$</tex> of 50-mesh XLPE powder and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3 \text{wt} \%$</tex> MAg-PE, achieving tensile strength of 23.9 MPa and elongation at break of 1336.68%. The dielectric strength reaches <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$44.97 \text{kV} / \text{mm}$</tex>, comparable to pure HDPE. Smaller XLPE particle sizes significantly enhance the tensile strength and elongation at break of the composites. The addition of MA-g-PE compatibilizer markedly improves interfacial bonding, mechanical properties, and electrical performance. This method offers an efficient, environmentally friendly route for XLPE waste recycling, demonstrating promising industrial application potential.