One-step enrichment of silica nanoparticles on milled carbon fibers and their effects on thermal, electrical, and mechanical properties of polymethyl-vinyl siloxane rubber composites

It is critical to develop new approaches of preparing engineered carbon-based fillers for high-performance applications. Herein, silica nanoparticles enriched milled carbon fibers (MCFs@SiO₂) as novel thermal conductive and electrical insulating filler was synthesized through a simple and rapid sol-gel reaction method within one hour before their incorporation into polymethyl-vinyl siloxane rubber (MVSR). Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectrometer (XPS) were applied to analyze the surface chemical structure of synthesized MCFs@SiO₂, results of which demonstrated the existence of unhydrolyzed oxyethyl groups that are beneficial to improve the compatibility with polymer matrix. Enrichment mechanism of silica nanoparticles on milled carbon fibers was also described. The MVSR composites with a 20 vol.% MCFs@SiO₂ loading showed 109.7% higher thermal conductivity compared to that of neat MVSR and an excellent electrical volume resistivity of 1.04 × 10⁹ Ω cm owing to the silica nanoparticles layer. Besides, their tensile strength increased by 145.7%, resulting from the good compatibility between MCFs@SiO₂ and MVSR which was confirmed by scanning electron microscope observations.