Physical recycling of polyimide waste films to improve friction and wear properties of rubber

The surge in polyimide (PI) film production has resulted in a significant accumulation of waste films. Thus, exploring rational recycling and reuse strategies for PI waste films is of great significance. In this work, PI waste film was ground into powder via liquid nitrogen pulverization, with a broad particle size distribution (DV10 = 5.692 μm, DV50 = 77.146 μm, DV90 = 376.913 μm) as characterized by a laser particle sizer. Different contents of PI powder (0 phr, 2.5 phr, 5 phr, and 7.5 phr) were blended with natural rubber (NR), followed by hot-press vulcanization to prepare NR/PI composites. The friction and wear properties of the composites were evaluated under room temperature, dry sliding conditions with a 5 N load. Experimental results demonstrated that PI powder derived from waste films not only enhanced the hardness but also reduced the friction coefficient of NR/PI composites. At 7.5 phr, the hardness increased by 5%, and the friction coefficient decreased by 13.83% with enhanced stability. Notably, at 2.5 phr PI content, the composite exhibited optimal PI-NR interfacial bonding, thermal stability, and wear performance: wear mass decreased by 30% and wear volume by 58.3% compared to neat NR.