Abstract

This study aimed to develop natural rubber/butadiene rubber (NR/BR) composites with low hardness, high abrasion resistance, and flame retardancy. Two flame-retardant plasticizers - triisopropyl phenyl phosphate with viscosities of 50 mm² /s (IPPP-50) and 95 mm²/s (IPPP-95) - were incorporated into NR/BR matrices. We systematically compared the effects of IPPP-50 and IPPP-95 on the composite's compatibility, hardness, flame resistance, and abrasion resistance. The results demonstrated that IPPP-95 exhibited superior compatibility with the rubber matrix. The incorporation of IPPP-95 effectively reduced composite hardness while maintaining abrasion resistance and enhancing flame retardancy. However, when used as the sole additive, IPPP-95 provided insufficient flame retardancy for NR/BR composites. Subsequent formulation optimization combining IPPP-95 with aluminum diethylhypophosphite and aluminum hypophosphite synergistically achieved reduced hardness, improved flame resistance, and preserved abrasion resistance. Notably, IPPP-95 showed negligible impact on the tensile strength of NR/BR composites. This phenomenon can be attributed to two mechanisms: (1) enhanced molecular chain mobility and (2) increased strain-induced crystallinity, both of which indirectly contribute to maintaining abrasion resistance. Additionally, IPPP-95's lubricating effect further preserved the composite's wear resistance.