Study on Lubricant Release-Recycle Performance of Porous Polyimide Retainer Materials

Oil-impregnated porous polyimide (PI) materials can provide continuous lubricant supply, which is widely used to manufacture space rolling bearing retainers. The lubrication performance of porous polyimide materials mainly depends on their ability to release and recycle lubricants, which is closely related to pore size. In this paper, to investigate the effect of pore size, porous polyimide materials with different pore sizes were prepared by preheating the retainer tube billet during the limit pressing process. The lubricant content rates at each stage were measured by the lubricant immersion and centrifugal release experiment to show the variation of the lubricant content rate in the porous PI sample during a working cycle. At first, the lubricant can be absorbed into the pore. It is found that the absorption rate is faster for lubricants with a smaller viscosity. Moreover, lubricant thinning caused by temperature rise also improves the absorption rate. After lubricant absorption to saturation, the lubricant is released under the centrifugal effect to provide the lubricant. Increasing pore size and using low-viscosity lubricants are the main ways to improve lubrication. Finally, the lubricant on the surface can be recycled into the pore by capillary effect. The smaller the pore size, the faster the lubricant recycles to saturation. These insights gained in this study can provide guidance for the choice of an oil-impregnated porous retainer in different working conditions.