Sustainable Silica Nanoparticles from Jasmine Rice Husk as Reinforcing Fillers for Natural Rubber Composites

This study reports the synthesis of silica nanoparticles from Thai jasmine rice husk (J) and their application as reinforcements in natural rubber (NR) nanocomposites. The influence of surfactant distribution and surface treatment of the silica on the mechanical properties and biodegradation behavior of the composites was systematically investigated. Silica nanoparticles (J-SiO₂) were prepared via a sol-gel method and incorporated into NR, which was subsequently vulcanized using electron beam irradiation at 200 kGy. The synthesized J-SiO₂ exhibited primary particle sizes of 10-20 nm and aggregated structures ranging from 40 to 110 nm, as observed by AFM. Surface treatment with Si-69 significantly improved nanoparticle dispersion within the rubber matrix, enhancing mechanical strength and viscoelastic properties. The inclusion of ammonium laurate (AL) as an anionic surfactant further promoted dispersion without compromising the mechanical performance of the composites. Biodegradation behavior was evaluated under natural soil burial conditions over six months. Both neat NR and NR/J-SiO₂ nanocomposites showed signs of microbial degradation. Notably, the NR nanocomposites exhibited a higher weight loss (11.7%) than virgin NR (5.8%), indicating that the incorporation of silica nanoparticles enhances the biodegradability of NR. These findings highlight the potential of agricultural waste-derived silica in developing sustainable, high-performance rubber materials.