Microporous formation and evolution mechanism of PTFE fibers/isotactic polypropylene membranes by interface separation

Abstract Studying microporous formation and evolution mechanism plays a crucial role in fabricating high-performance microporous membranes. A formation mechanism of PP microporous membranes, different from those reported previously, was proposed based on the interface separation of PTFE fibers and PP matrix during sequential biaxial stretching. The experimental results indicated that the initial microcracks, which were filled by microfibrillated PP, were originated from PTFE fibers-PP matrix interfaces perpendicular to the longitudinal stretching direction. As the strain increased, microfibrillated PP was further elongated, ultimately forming microfibrillated PP membranes at a relatively low strain (200%). The subsequent transverse stretching caused the separation of fibrillated PP to form an excellent microporous structure. As a result, PTFE/PP membranes after biaxial stretching exhibited the narrower pore size distribution, higher porosity, higher N2 flux and pure water flux than β-PP membranes.