Porous polyimide (PI) membranes are widely used in separation processes because of their excellent thermal and mechanical properties. However, the applications of porous PI membranes are limited in the nanofiltration range. In this study, porous PI membranes with through-holes have been successfully fabricated by the novel multiple solvent displacement method. This new method requires only a porous polyamic acid (PAA) membrane, which was prepared by immersing PAA film in N-methylpyrrolidoneebk; (NMP) prior to immersing it in a mixed solvent consisting of NMP and a poor solvent, followed by immersion only in poor solvent. The pore size, morphology, porosity, and air permeability demonstrated that the fabricated PI membranes had a uniformly porous structure with throughholes over their surface. This new method enabled control of pore size (3-11 μm) by selecting a suitable poor solvent. This multiple solvent displacement method is highly versatile and promising for the fabrication of porous PI membranes.
Ultra-high-molecular-weight polyethylene (UHMWPE) has been widely used in industry; however, the applications for UHMWPE are limited because of low hydrophilic and adhesive properties. Herein, we developed the surface properties of UHMWPE by using side-chain crystalline block copolymers (SCCBCs), which consist of a side-chain crystalline unit and a functional unit. This process only required immersing the UHMWPE film in the diluted SCCBC solution, which enabled the UHMWPE surface to be coated homogeneously. The results of the contact angle and tensile shear test showed that the surface of UHMWPE modified with SCCBC was improved in hydrophilicity and adhesive properties. In addition, high adhesion strength was measured on UHMWPE surfaces dipped in a SCCBC solution at high temperature with the UHMWPE film becoming elongated at all parts other than the adhesion contact area.
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