Enhancement in electrical and thermal performance of high‐temperature vulcanized silicone rubber composites for outdoor insulating applications

Research on Postcuring Parameters Effect on the Properties of Fiberglass-Reinforced Silicone Resin Coil Bobbin

With the growing demand for insulation parts in extreme service environments, such as nuclear power, aviation, and other related fields, fiberglass-reinforced silicone resin (FRSR) has become a popular choice due to its exceptional physical and chemical properties in high-temperature and electromagnetic working environments. To enhance the performance of FRSR molded parts that can adapt to more demanding extreme environments, the oven postcuring process parameters on thermal stability and mechanical properties of the bobbin were investigated. The curing behavior of FRSR was analyzed by using thermogravimetric analysis (TGA) and the differential scanning calorimetry (DSC) method, and the bobbins were manufactured based on the testing results. Subsequently, the bobbins were oven postcured at different conditions, and the heat resistance and mechanical properties were analyzed by TGA and tensile tests. The results revealed that the tensile strength of the bobbin increased by 122%, and the weight loss decreased by 0.79% at 350 °C after baking at 175 °C for 24 h. The optimal process parameters for producing bobbins to meet the criteria of nuclear installations were determined to be a molding temperature of 120 °C, molding pressure of 50 MPa, pressure holding time of 3 min, oven postcuring temperature of 175 °C, and postcuring time of 24 h. The molded products have passed the thermal aging performance test of nuclear power units.

Preparation of High-Strength and Excellent Compatibility Fluorine/Silicone Rubber Composites under the Synergistic Effect of Fillers

Fluorine/silicone composite rubber is widely used as a sealing material in aerospace, missile, automotive, petroleum, and other industries, but the traditional process does not use synergistic fillers to strengthen the composite system. In this research, fumed SiO₂ and black caron (N990) were used as synergistic fillers, fluorine/silicone composite rubber was prepared by mechanical mixing process, and three different fluorine rubber systems were used to find the best composite material. The mechanical properties, thermal properties, aging properties, moderate strength properties, and microstructure of the composites were evaluated. Studies have shown that mixing the two can produce a certain interface interaction and effectively improve the compatibility. The physical properties of the material tended to decrease during the increase in the added amount of silicone rubber (MVQ). The maximum tensile strength of the hybrid material can reach 15 MPa. The optimal mixing ratio is fluororubber/silicone rubber (FKM/MVQ) = 9/1. At this time, the mechanical properties of the composite material are in the best state, and SiO₂ and black caron (N990) have a reinforcing effect, which can effectively improve the mechanical properties. After the composite was kept at 200 °C for 48 h, the tensile strength and elongation of the best sample A1 were 99.5 and 97.0%, respectively, showing excellent anti-aging properties. This work provides a method to fabricate high-strength fluorine/silicone composites using synergistic fillers that may be used in heat-medium-sealed environments.

On the icephobicity of damage-tolerant superhydrophobic bulk nanocomposites

To address the increase in demand for superhydrophobic and icephobic surfaces with greater mechanical robustness, we fabricated damage-tolerant, abrasion-insensitive, and icephobic superhydrophobic bulk nanocomposites using a facile, cost-effective, industrially applicable, and environmentally benign strategy. We prepared nanocomposites composed of high-temperature vulcanized silicone rubber through the highly controlled incorporation of nanosized fumed silica and microsized aluminum trihydrate particles. The produced nanocomposites did not require additional processing, such as sand abrasion or plasma treatment, to acquire their superhydrophobic properties. The extended roughness throughout the whole bulk of the nanocomposites imparted the volumetric superhydrophobicity and resistance to mechanical damage. The presence of micro-nanoparticles also enhanced the thermal stability and icephobic properties of the silicone rubber. The icephobic behavior of the developed nanocomposites was assessed based on freezing delay and push-off tests both of which denoted improved icephobic properties, i.e., high freezing delay time and low ice adhesion strength. We verified the extended duration of superhydrophobicity within the bulk nanocomposite using sandpaper abrasion, severe cutter scratching, tape peeling, and water-jet impacts. This study represents the first evaluation, to the best of our knowledge, of the icephobic properties of both the surface and bulk of the produced nanocomposite subjected to several cycles of sandpaper abrasion. Interestingly, even after multiple abrasion cycles, the samples demonstrated considerably low ice adhesion strength confirming their bulk icephobicity. In a nutshell, our findings are very promising for the fabrication of mechanically robust icephobic materials.