SEM Image Analysis of Pore Structure of Extending PTFE Membrane

Abstract

The pore structure of extending PTFE(ePTFE) membrane by the stretching method is much different from other polymers. The image analysis of Scanning Electron Microscope(SEM) was used to describe the fiberized PTFE molecular and the coagulated PTFE node. The interconnected notes and fibrils were defined as numerical parameters, LF, WF, LN, WN and AN. The results by description of the SEM image analysis were corresponding with the porosity Pr and density Pf in the combination method of bubblepressure and fluid permeability used in other microporous membranes. The membrane with bigger AN images of node gave larger Pf and smaller Pr, and membrane with smaller AN images showed smaller Pf and bigger Pr. However there was no certain relationship with r or rmax. It is said that the SEM image analysis can be used as one of the methods to describe the pore performance of ePTFE membrane. Moreover, the influences of molecular weight of PTFE, and the stretching ratio at mechanical operation on ePTFE pore structure could also be interpreted by the SEM image analysis. The bigger molecular weight of raw material PTFE, the higher porosity and strength of the membrane would be found. The less stretching ratio, the bigger crystal node and the shorter fibril SEM image were observed.