The effect of thermal aging on the mechanical properties and thermal stability of modified polypropylene insulating materials

As a novel cable insulation material, thermoplastic polypropylene (PP) offers advantages such as excellent electrical properties, good chemical corrosion resistance, and a relatively high temperature rating, aligning with China's current "dual-carbon" goals. Two types of modified PP insulation materials are investigated: blend-modified and copolymer-modified. Accelerated thermo-oxidative aging tests were conducted at different temperatures and durations. Variations in mechanical and thermal properties before and after aging were characterized using tensile testing, dynamic thermomechanical analysis (DMA), and thermogravimetric analysis (TGA). The performance differences between the two modified PP materials and XLPE were systematically analyzed. Results indicate that both XLPE and PP undergo oxidative degradation and a decline in mechanical performance during thermo-oxidative aging. However, PP demonstrates overall superior aging resistance. XLPE degrades relatively slowly in the initial aging stage but suffers rapid performance deterioration later due to the breakdown of its cross-linked network structure. In contrast, while PP exhibits a faster oxidation rate, it maintains better mechanical property retention and thermal stability than XLPE. Specifically, the blend-modified PP, toughened by elastomers, shows the best toughness and ductility, with the smallest decrease in mechanical properties. The copolymer-modified PP, owing to its high crystallinity, possesses more excellent thermal stability. Both modified polypropylene materials demonstrate potential for replacing XLPE as cable insulation.