117 / 2021-11-30 16:26:37

Friction behavior of oil impregnated porous polyimide material with different porosities and pore sizes

polyimide; porous material; friction mechanism; polymer

Three kinds of porous polyimide material with different densities were made and Stribeck curves and sliding-rolling rate (SRR) curves were tested to investigate friction behavior of the materials. A flow shape test rig was constructed to observe the oil spilling condition dynamically during sliding. Results indicate that the small amount of oil impregnated in micro pores could lubricate the contact surfaces effectively, but the hydrodynamic pressure will be unloaded to varying degrees depended on pore size and porosity. Low-density iPPI material impregnated more oil but the friction is the highest, and additional oil is not conducive to the reduction of friction coefficient. High- density iPPi materials behave elastohydrodynamic regime, and additional oil make friction lower under high speed. When the SRR is above 5 %, low-density iPPI material performs shear thinning, the friction coefficient decreases with SRR, while high-density iPPI material exhibits “shear thickening”, the friction coefficient increases linearly with SRR. This investigation provides the details of friction behaviors of iPPI material, which helps to better understanding of friction mechanisms of porous material used in artificial cartilage, bearing cage, etc.