In polymer composites such as plastics, rubber, and coatings, inorganic fillers (such as calcium carbonate, talc, and silica) are often added to reduce costs or improve mechanical properties. However, these hydrophilic fillers have poor compatibility with the hydrophobic polymer matrix, easily leading to problems such as uneven dispersion, weak interfacial bonding, and material embrittlement. In this case, n-octyltrimethoxysilane becomes a crucial "interfacial bridge."

By mixing the filler with a small amount of n-octyltrimethoxysilane, the methoxy group of the silane reacts with the hydroxyl group on the filler surface, "encapsulating" it with an organooctyl chain. This not only changes the filler from hydrophilic to hydrophobic but also enhances its wettability and dispersibility in the resin or rubber. The result is a significant improvement in the tensile strength, impact toughness, and processing fluidity of the composite material, while reducing agglomeration and sedimentation.

For example, adding silane-treated calcium carbonate to polypropylene (PP) can increase the filler content to over 40% without significantly sacrificing performance, and also improve the surface finish of the product. In silicone rubber cable materials, using silane to treat silica can reduce mixing energy consumption and improve dielectric properties. This "small dosage, big effect" surface modification technology has become an important part of the industrial production of high-performance composite materials.