Sho Hirai

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 through‐holes 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.

The consumption of polypropylene (PP) has significantly increased over that of other materials because of its light weight, easy molding, and high mechanical strength. However, the applications of PP are limited, owing to the lack of surface properties, especially with respect to adhesive properties and hydrophilicity. In this study, we developed a surface modification method for enhancing the adhesive properties and hydrophilicity on the PP surface using a side-chain crystalline block copolymer (SCCBC). This method was simple and involved the dipping of a PP film in a diluted SCCBC solution. The optimized modification conditions for enhancing the adhesive properties of PP were investigated. The results revealed that the adhesion strength of PP modified with the SCCBC of behenyl acrylate and 2-(tert-butylamino)ethyl methacrylate was enhanced to 2.00 N/mm (T-peel test) and 1.05 N/mm² (tensile shear test). In addition, the hydrophilicity of PP modified with the SCCBC of behenyl acrylate and di(ethylene glycol)ethyl ether acrylate was enhanced to a water contact angle of 69 ± 4°. Surface analysis was also performed to elucidate a plausible mechanism for PP modification by the SCCBCs. This surface modification method is facile and enhances desirable properties for the wide application of PP.

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.

While polyethylene is widely used in consumer products, its use in other applications is limited because of low adhesive properties. In this study, the adhesive properties of high-density polyethylene were improved by a facile chemical treatment which was no require the special equipment or reagents. This simple treatment enabled the homogeneous modification of a polyethylene surface by dipping in a dilute solution containing a side-chain crystalline block copolymer (SCCBC) for a short time. SCCBC comprises of a block copolymer with one monomer containing long alkane side chains that form the side-chain crystalline units and the other that contains functional monomers. The adhesive strength of the high-density polyethylene film modified by SCCBC, as determined using a T-peel test and tensile shear test, was stronger than the non-modified high-density polyethylene substrate. Furthermore, this facile method imparted these strong adhesive properties to high-density polyethylene over a wide variety of treatment conditions such as temperature of SCCBC solution, concentration, dipping time and types of solvent.