Mechanical and Insulating Properties of Polypropylene/Propylene-Based Elastomer Composites Over a Wide Temperature Range

There is a growing demand for environmentally friendly polypropylene (PP) cable insulation materials. Research focuses on synergistically enhancing the mechanical toughness and high-temperature electrical insulation properties of PP-based composites. In this study, a twin-screw extruder was used to blend and extrude a high-melting-point crystalline propylene-based elastomer (PBE) with PP. The crystalline and trap characteristics of the composite material were leveraged, and the influence of PBE on the wide-temperature-range mechanical and electrical properties of PP composites was investigated and analyzed. Results demonstrate that PBEmodified PP composites exhibit remarkable improvements: elongation at break increased by over 160 %, and tensile strength increased by more than 9.01 MPa compared to pure PP. Notably, the composite containing <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$20 \text{wt} \%$</tex> PBE achieved a breakdown field strength of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$372.40 \text{kV} / \text{mm}$</tex> at 90° C. This value approaches that of pure PP, effectively maintaining the material's insulation performance. Synergistic interaction between PP's rigid crystals and the flexible crystals nucleated by PBE underpins the observed enhancement. Consequently, the resulting crystalline structure exhibits excellent thermal stability coupled with a high density of deep traps.