Silane‐Functionalized Rice Husk Silica as a Sustainable Reinforcement for High‐Performance Bio‐Epoxy Composites

ABSTRACT While rice husk silica has been explored as a low‐cost filler for conventional epoxies, the synergistic effect of complementary organosilanes—an epoxy‐functional GLYMO and an amino‐functional APTMS—on biogenic silica tailored for a partially bio‐based epoxy matrix has not been systematically investigated. Here, b‐Epoxy composites were prepared in three variants (unmodified b‐Epoxy/SiO 2 , amino‐functionalized b‐Epoxy/SiO 2 ‐AM, and epoxy‐functionalized b‐Epoxy/SiO 2 ‐EP) and characterized through a concerted FTIR/NMR/SEM/TEM/DMTA analytical sequence. Three advances emerge: (i) systematic benchmarking of GLYMO versus APTMS chemistry on the same biosilica source; (ii) identification of 5 wt% as the optimal filler loading for simultaneous tensile and stiffness reinforcement; and (iii) direct correlation of interfacial chemistry with thermomechanical stability. The GLYMO‐functionalized b‐Epoxy/SiO 2 ‐EP system delivered the most balanced performance—tensile strength ≈58 MPa at 5 wt% (significantly higher than 52 MPa for b‐Epoxy/SiO 2 ‐AM, and 46 MPa for the unmodified composite), Young's modulus up to ≈740 MPa, microhardness of 395 MPa (vs. 175 MPa for the neat bio‐matrix), and a T g shift from 96.17°C to 108°C–110°C. The same bio‐resin platform was extended to alkali‐treated flax‐fabric laminates (flexural strength 146.4 MPa) and validated by a cradle‐to‐functionalized‐silica E‐factor of 3.19–4.12 kg/kg—one‐to‐two orders of magnitude lower than conventional fumed silica—establishing silane‐functionalized biosilica as a tunable, circular route to high‐performance bio‐based composites.