Two-step thermal infiltration and crystallization of solvent for preparation of nanoporous polypropylene membranes

초록

Nanoporous polypropylene (PP) membranes are increasingly vital for diverse applications, driving the demand for facile fabrication methods that yield controlled pore structures and high performance. This study introduces a novel approach for creating PP membranes with aligned nanopores through a two-step thermal infiltration and directional crystallization process. A crystallizable solvent, arachidic acid (AA), is thermally infiltrated into PP films, followed by directional crystallization under a temperature gradient. Subsequent selective extraction of the crystallized AA results in the formation of internally aligned nanopores. To enhance porosity and interconnectivity, a two-step infiltration strategy was employed—initial infiltration at a high temperature (160 ℃), followed by isothermal holding at intermediate temperatures (130–150 ℃). This approach enabled precise control over crystallization kinetics with maintaining PP crystalline phases, leading to the formation of improved nanopore networks. As a result, membranes with a porosity up to 56% exhibited improved filtration flux. Thermal analysis and mechanical testing revealed that the crystallinity and mechanical strength of the membranes varied significantly depending on the thermal infiltration history. The proposed method shows great potential for the development of environmentally friendly, scalable, and high-performance functional membranes.

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