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.

Tetraethyl orthosilicate (TEOS) was used as the silicon source, and polydimethylsiloxane (PDMS) was the organic precursor to modify the surface of glass ber (GF) through the sol-gel method. The modi ed GF noted T-GF was lled in PTFE to prepare PTFE/T-GF composites. SEM, FTIR, XPS, and contact angle con rmed that organic-inorganic hybrids were successfully loaded on GF's surface. Compared with PTFE/GF and the conventional coupling agent modi ed GF lled PTFE composites, the properties of PTFE/T-GF composites, including dielectric properties, mechanical properties, moisture absorption, thermal conductivity, and coe cient of thermal expansion (CTE), enhanced signi cantly for the improvement of compatibility of PTFE and GF. Moreover, the PTFE/T-GF exhibited improved dielectric constant (2.305), decreased dielectric loss (9.08E -4 ), higher bending strength (21.45 MPa) and bending modulus (522 MPa), better thermal conductivity (0.268 W/m*K) and lower CTE (70 ppm/℃), making it has promising application as the substrate materials for printed circuit board.

In this article, polytetrafluoroethylene (PTFE) microporous membranes with excellent tensile strength and good wear durability were successfully fabricated by the addition of nano-alumina (Al2O3). The friction and mechanical behavior of PTFE microporous membranes with different nano-Al2O3 contents were investigated by Martindale abrasion tester, dynamic mechanical analysis, and universal testing machine. Scanning electron microscopy was applied to analyze the surface, longitudinal section, and worn surface of the microporous membranes. Results demonstrated that nano-Al2O3 particles were dispersed into the “node” structures of PTFE microporous membranes and acted as the skeleton, leading to the increasing of the tensile strength remarkably. The wear rate reduced significantly with the addition of nano-Al2O3 and was affected by nano-Al2O3 content. Additionally, the wear mechanism of the microporous membranes was also discussed based on the study results.