Enhancing interfacial strength and hydrothermal aging resistance of silicone resin composites by different modification of carbon fibers with silica nanoparticles

Abstract

Besides the well‐designed combination of the fibers and matrix resin, the fiber‐matrix interface plays a key role in bulk properties of composites. Here, the chemical grafting of silica nanoparticle (SiO2) onto fiber surface (CF‐g‐SiO2) using the bridging toluene‐2,4‐diisocyanate has been achieved and compared with the physical adsorption one (CF‐ad‐SiO2). Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy confirmed the covalent bonding nature between SiO2 and CF. By atomic force microscopy observation, coating or grafting SiO2 on the surface of CFs also enhanced fiber surface polarity and roughness. However, CF‐g‐SiO2 showed a better uniform distribution of SiO2 on the fiber surface compared with CF‐ad‐SiO2 with the serious agglomeration of SiO2. These results of dynamic contact angle measurements indicated that CF‐ad‐SiO2 and CF‐g‐SiO2 had the similar increase degree of surface free energy, which contributed to improve the wettability between CFs and matrix resin. Interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) showed great enhancements, especially for CF‐g‐SiO2 composites, which increased 10.92% in ILSS and 10.71% in IFSS compared with those of CF‐ad‐SiO2 composites. Moreover, the interfacial reinforcing mechanisms have also been studied. Additionally, the introduced Si‐O‐Si bonds at the interface by SiO2 coating or grafting resulted in the different improved degree of the hydrothermal aging resistance. The results showed that the quality of fiber‐matrix interface could be tuned by varying the bonding natures between CFs and the modifiers, and chemically grafting SiO2 onto the fiber surface is the promising multifunctional reinforcement. POLYM. COMPOS., 40:E975–E982, 2019. © 2018 Society of Plastics Engineers

Effects of alkyl/vinyl‐modified nanosilicas on negative or positive high voltage direct current breakdown strength and tensile properties in silicone rubber nanocomposites

“…Therefore, electrical, physical, and mechanical properties are affected negatively by the bad interfacial characteristics. [14][15][16] When external stress such as electrical, mechanical and heat stress are applied to a nanocomposite, micro-cracks are generated at weak interfaces, propagated and fractured. 12,17 To modify the interfacial characteristics, the nanosilica surface should be treated with hydrophobic alkyl or vinyl groups using coupling agents.…”

“…However, since the affinity between hydrophobic silicone rubber and hydrophilic nanosilica is low, it is very difficult to disperse uniformly the nano‐sized fumed silica in the silicone rubber, so the nanosilica particles exist in agglomerated state in the silicone rubber. Therefore, electrical, physical, and mechanical properties are affected negatively by the bad interfacial characteristics 14–16 . When external stress such as electrical, mechanical and heat stress are applied to a nanocomposite, micro‐cracks are generated at weak interfaces, propagated and fractured 12,17 .…”

Facile preparation of hyperbranched polysiloxane‐grafted carbon fibers with improved interfacial strength of silicone resin composites

“…Carbon fibers (CFs), which are characterized by lightweight, strong strength, good thermal stability, high weathering resistance and radiation resistance, are widely used as the ideal reinforcing materials for polymers or matrix in various fields such as aerospace, automobile, chemical industry, textile and so on . The properties of composites are influenced not only by the inherent characteristics of CFs and matrix resin but also by the quality of their interface .…”

Chemical grafting of salicylaldehyde onto carbon fiber for enhancing interfacial strength of silicone resin composites

“…Carbon fibers (CFs) have the advantages of light weight, high hardness, good corrosion resistance, high‐temperature resistance, and good electrical and thermal conductivity, which are extensively used in aerospace, aerospace, automobile, and many manufacturing industries . It is widely accepted that the quality of fiber‐matrix interface influences its performance deeply, controlling the stress transfer efficiency between CFs and matrix resin .…”