Glass fiber, due to its high strength, heat resistance, and electrical insulation, is widely used in wind turbine blades, automotive parts, circuit boards, and building materials. However, untreated glass fiber has a highly hydrophilic surface and poor compatibility with resin matrices (such as epoxy and polyester), easily leading to poor interfacial bonding and decreased mechanical properties in composite materials. In this case, methyltrimethoxysilane becomes a crucial "interfacial bridge."

During glass fiber production, it is often impregnated in a coupling agent solution containing methyltrimethoxysilane. The methoxy groups of the silane molecules chemically bond with the silanol groups (Si–OH) on the glass surface, while the methyl groups face outwards, forming a hydrophobic molecular layer compatible with organic resins. This not only significantly improves the bond strength between the fiber and resin but also enhances the composite material's resistance to damp heat, fatigue resistance, and long-term stability.

For example, in the manufacture of large wind turbine blades, using glass fiber cloth treated with methyltrimethoxysilane allows the blades to maintain structural integrity and extend their service life under high humidity and high salt spray environments. Meanwhile, since methyl groups are non-reactive groups, they do not interfere with the subsequent curing reaction of the resin, making it particularly suitable for high-performance composite material systems with strict process window requirements. This "molecular-level coating" technology is an indispensable part of modern advanced composite materials.