Balancing the Mechanical Toughness and Electrical Insulation of Polypropylene by Blending and Grafting Modifications

Abstract

Balancing the mechanical toughness and electrical insulation of polypropylene (PP) for recyclable cable insulation application has attracted increasing attention. Due to the different molecular conformation, isotactic polypropylene (IPP) always delivers excellent electrical insulation but poor mechanical toughness, while block polypropylene (BPP) has been dramatically opposed properties. Blending IPP with BPP at an appropriate content may be beneficial to reconcile the toughness and insulation. In this study, the blending ratio of IPP and BPP is first investigated, and it is found that 60: 40 wt.% is the optimized ratio for achieving outstanding overall performance. Furthermore, polyolefin elastomer (POE) and styrene-grafted POE (POE-g-St) are incorporated into IPP/BPP blends respectively to intensify the toughness as well as the insulation property. The microstructure, electrical properties, mechanical properties, and thermal properties of the composites are systematically analyzed and discussed. The results demonstrate that the composite with a grafting ratio of 1.21 wt.% styrene exhibits superior overall performances, the enhanced breakdown field strength of 314.02 kV mm^−1, and reduced elastic modulus of 352.54 MPa are achieved. Additionally, the modified composites also possess a high melting temperature, high volume resistivity, and excellent space charge suppression capability, achieving the synergistic improvements of the electrical, mechanical, and thermal properties.