Investigation of Extrusion Fibrosis of PTFE Microporous Film During Extrusion Process Based on Air Permeability Experiments and Theoretical Analysis

The proportions of fiber, node, and pores on unit area of PTFE film were analyzed by image recognition. The relationship between the permeability and fibrosis degree was established based on air permeability experiments combined with theoretical analysis by using computational fluid dynamics (CFD) numerical simulation of the PTFE extrusion fibrosis process. With the particle tracing method, the independence of the particle number on the time step was simulated. The influences of the PTFE die cone angle, aspect ratio, compression ratio, and blank pushing speed were investigated. The simulation results are well consistent with those from experimental measurements, further verifying the reliability of the CFD simulation method of extrusion fibrosis. It is concluded that the cone angle, aspect ratio, and pushing speed have little effect on the export fibrosis index, while the average export fibrosis index increases with the compression ratio. Greater pushing force is required to achieve improved air permeability uniformity.