Combined effects of nanoparticle and stretch‐induced orientation on crystal structure and properties of UHMWPE/TiO₂ composite microporous membranes

Abstract The nanocomposite microporous membrane of ultra‐high molecular weight polyethylene (UHMWPE) and nano‐titanium dioxide (nano‐TiO₂) system was prepared by combining the thermally induced phase separation (TIPS) technique with the extrusion‐casting process using liquid paraffin (LP) as the diluent. The effects of variations of TiO₂ content and melt draw ratio on the properties of composite microporous membranes were studied and the optimal processing parameters were further investigated. ATR‐FTIR demonstrated that nanocomposite microporous membranes were successfully prepared. The crystallization behavior and morphological evolution of membranes were systematically investigated by WAXD, 2D‐SAXS, and SEM. It was found that the stretch‐induced orientation of UHMWPE was promoted and the shish‐kebab structure was formed for the reason of addition of TiO₂. The mechanism of combined effects of nanoparticles and stretch‐induced orientation on the crystallization behavior of UHMWPE was further discussed and explained. Compared to pure UHMWPE film, the permeability of the optimum performance film was significantly improved, with porosity of 49% and pure water flux of about 193 L m⁻² h⁻¹. Mechanical studies showed that nanoparticles and DR have significant effects on tensile strength and elongation at break. In addition, the thermal stability of composite microporous membranes was found to be improved with the increase of TiO₂ content and melt draw ratio. Thus, this investigation delivers inspiration for the expansion of excellent performance microporous membranes used for battery separators and filtration devices.