Glass Cloth Reinforced Ptfe Through The Composite

Polytetrafluoroethylene(PTFE) is a promising resin matrix with great potential to wave-transparent composites owing to its good dielectric properties, wide working temperature range, high temperature resistance, erosion resistance, rain resistance and excellent resistance to thermal shock.. However, PTFE is not qualified as structural wave-transparent material because of its poor mechanical properties. Glass fabric (GF) is a kind of reinforcing agent with high strength and low dielectric loss. It is of great interest to study glass fabric reinforced PTFE (GF/PTFE) composites with excellent dielectric properties and good mechanical properties.This study conducted systematic analysis and discussion on the molding process determination, interfacial modify and properties of the wave-transparent GF/PTFE composites as well as the influences of processing factors, aiming to solve some vital problems during the preparation of GF/PTFE composites, such as very complex molding process and poor interfacial adherence.Wave-transparent GF/PTFE composites were prepared according to following three steps: PTFE dispersion infusing GF, pressure molding and sintering. The molding process was optimized and determined through the analysis of the effects of each technical factors on the dielectric properties, mechanical properties and other performances. Results showed that the optimum technical factors for molding with 40wt% of GF is below: molding pressure 45MPa, holding for 40min, sintering process: 330/1 h+380/2h, heating rate 50/h. However, mechanical properties of the composites as prepared didn't satisfy the using demand for structural wave-transparent composites because of the poor interfacial adherence.The coupling agent SG-Si900, rare-earth solution containing SG-Si900 and rare-earth solution were used to treat the surface of GF and eventually modified the interface of GF/PTFE composites. SEM was used to observe the interfacial adherence of the composites under different surface treatment. The modifying mechanisms and effects of three modifiers were analyzed and evaluated throughthermodynamic calculation. Mechanical properties, dielectric properties, water absorption and thermal expanding coefficients were measured. It was found that the 0.3wt% rare-earth solution, which could obviously improve the mechanical properties of the composites, had the best modifying effects on the interfacial properties. While, the GF/PTFE composites as prepared were still not qualified as the structural wave-transparent materials.Moreover, in order to improve the mechanical properties of GF/PTFE composites further, cyanater ester resin (CE) infused GF/PTFE composites (GF/CE/PTFE) was suggested. Infusing process with CE was studied. The reinforcing effects and mechanism of CE infusing on the mechanical properties of composite were analyzed. The dielectric properties, water absorption and thermal expansion coefficients of GF/CE/PTFE composites were studied. It was found that when the porosity of GF/PTFE composite was 25%, the GF/CE/PTFE composite containing 14.4wt% of CE resin, possessing the optimum mechanical properties besides excellent dielectric properties, can be used as structural wave-transparent materials.Finally, the effects of environmental factors on the properties of GF/CE/PTFE composite were studied. The change of dielectric constant of GF/CE/PTFE under various humidities, temperature and frequency were studied. Many experiments such as water boiling, thermal cycling, UV radiation were carried out to study the effects of environmental factors on composite mechanical properties. It turned out that the dielectric constants of the GF/CE/PTFE composite changed greatly with humidities varying, while it was steady when temperature and frequency changed. Mechanical properties and thermal expansion coefficient were greatly influenced by wet and hot conditions but were hardly affected by thermal cycling and UV radiation.