Polyvinyl alcohol (PVA)/carboxyl methyl cellulose sodium (CMC)/Na₂CO₃ composite films with different contents of Na₂CO₃ were prepared by blending and solution-casting. The effect of Na₂CO₃ on the microstructure of PVA/CMC composite film was analyzed by Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and atomic force microscopy (AFM). Its macroscopic properties were analyzed by water sorption, solubility, and dielectric constant tests. The results show that the microstructure of PVA/CMC/Na₂CO₃ composite films was different from that of PVA and PVA/CMC composite films. In addition, compared to PVA and PVA/CMC composite films, the water sorption of PVA/CMC/Na₂CO₃ composite films relatively increased, the solubility in water significantly decreased, and the dielectric properties significantly improved. All these results indicate that the hydrogen bonding interaction between PVA and CMC increased and the crystallinity of PVA decreased after the addition of Na₂CO₃. This was also a direct factor leading to increased water sorption, decreased solubility, and enhanced dielectric properties. The reaction mechanism of PVA, CMC, and Na₂CO₃ is proposed to further evaluate the effect of Na₂CO₃ on the microstructure and macroscopic properties of PVA/CMC/Na₂CO₃ composite films.

The composite films based on polyimide (PI) and chloride modified carbon black (CB-COCl) were prepared by conversion of biphenyltetracarboxylic dianhydride and 4,4′-oxydianiline in the presence of CB-COCl, followed by thermal imidization. The presence of chemical bonds between PI and CB-COCl, proved by FTIR spectra of the composites, has a considerable effect on the properties of PI films. Scanning electron microscopy (SEM) pictures of the PI/CB-COCl membranes showed changed morphology compared to reference membranes without CB-COCl. The thermal stability and structure of the composites were studied by differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) and X-ray diffraction (XRD), respectively. These hybrid films showed an increase in thermal decomposition temperature and a slightly enhanced glass transition temperature. On their mechanical properties, the modulus and ultimate strength of the hybrid films increased and elongation at break decreased with increased CB-COCl content. The surface free energy of polyimide films were determined by means of the contact angle measurements.

Polytetrafluoroethylene (PTFE) capillary membranes, known for the great chemical resistance and thermal stability, are commonly used in membrane separation technologies. However, the strong hydrophobic property of PTFE limits its application in water filtration. This study introduces a method whereby acrylamide (AM), N, N-methylene bisacrylamide (MBA), and vinyltriethoxysilane (VTES) undergo free radical copolymerization, followed by the hydrolysis-condensation of silane bonds, resulting in the formation of hydrophilic three-dimensional networks physically intertwined with the PTFE capillary membranes. The modified PTFE capillary membranes prepared through this method exhibit excellent hydrophilic properties, whose water contact angles are decreased by 24.3–61.2%, and increasing pure water flux from 0 to 1732.7–2666.0 L/m²·h. The enhancement in hydrophilicity of the modified PTFE capillary membranes is attributed to the introduction of hydrophilic groups such as amide bonds and siloxane bonds, along with an increase in surface roughness. Moreover, the modified PTFE capillary membranes exhibit chemical resistance, maintaining the hydrophilicity even after immersion in strong acidic (3 wt% HCl), alkaline (3 wt% NaOH), and oxidative (3 wt% NaClO) solutions for 2 weeks. In conclusion, this promising method yields modified PTFE capillary membranes with great hydrophilicity and chemical resistance, presenting substantial potential for applications in the field of water filtration.