Abstract:

This study compares the properties of microporous membranes fabricated from two domestic polytetrafluoroethylene （PTFE） resins with different molecular weights against two commercial benchmarks （Daikin F⁃106 and F⁃104C）. The influence of molecular weight on the microscopic morphology， thermomechanical properties， and mechanical performance of the stretched membranes was systematically investigated. The results indicated a strong structure⁃property relationship： the high molecular weight （HMW） PTFE resin facilitated the formation of a microstructure characterized by short fibers and small junctions. This structure yielded a membrane with a small pore size （0.22 μm）， high tensile strength （7.1 MPa）， but lower air permeability. Conversely， the low molecular weight （LMW） resin produced long fibers and large junctions， resulting in a membrane with a larger pore size （0.71 μm）， higher gas permeability ［33 L/（m²·s）］， and lower strength （3.3 MPa）. Furthermore， crystallinity analysis revealed that the HMW membrane had a lower crystallinity （69.72 %） compared to the LMW membrane （82.82 %）， suggesting greater crystal structure damage and weaker recrystallization ability during processing. These findings demonstrate that molecular weight is a critical parameter for tailoring PTFE microporous membranes for specific applications， with HMW resins favoring small⁃pore， high⁃strength membranes and LMW resins enabling high⁃permeability variants.

Key words: polytetrafluoroethylene, stretching, microporous membrane, molecular weight