Identification of Pore‐Forming Development in <scp>PTFE</scp> Microporous Membranes Under Thermo‐Mechanical Stretching

ABSTRACT Polytetrafluoroethylene (PTFE) is widely used for membrane preparation due to superior thermal stability, chemical inertness, and high fracture toughness. Elucidating the stretching mechanism is essential for the cost‐effective production of PTFE microporous membrane with optimized structure and performance. In this study, a series of PTFE microporous membranes were prepared via thermo‐mechanical stretching under various processing conditions. The results showed that the microcrack initiation occurred at the early stage of stretching. The specific point on the stress–strain curve where microcrack formation commences was identified as the stretching induced pore‐forming point. Through mechanical characterization and scanning electron microscopy (SEM) analysis, this pore‐forming point was established to coincide with the yield point. Notably, a rightward shift of this pore‐forming point on the stress–strain curve promotes microcrack development, and its displacement trend enables prediction of microstructural evolution in the membranes. Furthermore, increasing the stretching ratio significantly enhances membrane porosity and hydrophobicity.