Smart polymer self-lubricating material: Optimal structure of porous polyimide with base oils for super-low friction and wear

In the contemporary pursuit of ensuring long-term lubrication for transmission units operating under harsh conditions, significant challenges remain. Researchers have been investigating porous polymer materials as a potential solution; however, achieving exceptionally low friction and wear has proven elusive. To address this issue, we have developed a novel porous fluorinated polyimide (PPIF-250) characterized by superior mechanical performance, heat resistance, and higher oil content and retention compared to other PPIs with comparable pore size and porosity. Extensive lubrication testing under varying conditions has demonstrated that PPIF-250 achieves remarkably low friction and wear characteristics, even under high FV values, representing a significant advancement in this field. Furthermore, our findings indicate that the polarity of base oils plays a crucial role in determining the oil content and retention of PPIF-250. Specifically, the integration of PPIF-250 with a tailored PEG-200 structure results in significantly improved oil content, retention, and long-term lubrication relative to other base oils. This improvement is attributed to the formation of high-load capacity boundary films within the PPIF-250 matrix, comprising oxidation processes involving carboxyl functional groups that chelate with iron or its oxides, alongside multi-layer adsorption films stabilized by intermolecular hydrogen bonding and Van der Waals forces. These insights will be instrumental in the development of more efficient and effective lubrication materials to meet the demands of modern technology.