Effect of Porosity on Oil Migration and Capillary Oil Absorption Characteristics in Porous Polyimide

A microscopic model with a high degree of polyimide (PI) pore structure reproduction was constructed using the quartet structure generation set method and slicing technique. Based on finite element method, a visual simulation of PI porous models with different porosities was performed. The migration characteristics of lubricating oil within models of varying porosities under the influence of centrifugal force, as well as the impact of porosity on capillary oil absorption properties, were thoroughly analyzed. Results shown that the increase in porosity leaded to a rising trend in the lubricating oil content within the porous PI model, indicating that under the influence of centrifugal force, the migration amount of lubricating oil increases with the increase in porosity. When considering only capillary forces, the volume fraction of lubricating oil and the oil level line within the porous PI model initially rised rapidly and then tended to stabilize as porosity increases. This demonstrated that the increase in porosity significantly promoted the capillary oil absorption process. The primary reason is that the increased porosity allows more pores to participate in oil absorption through capillary forces, thereby increasing the oil content. However, when the porosity is too high, pore merging occurs, which weakens the capillary force effect.