In this paper, silicate filler modified with silanes (3-aminopropylsilanetriol, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, hexamethyldisilazane and 3-glycidoxypropyltrimethoxysilane) and industrially processed filler R 711 were studied. By definition, fillers are particulate materials that are added to polymers to improve the physical properties and/or reduce the cost of the composite. The surface of natural fillers based on silicon dioxide, SiO2, is partially or completely hydrated and therefore hydrophilic. By depositing organic substances on the hydrophilic surface of natural and synthetic inorganic fillers, their dispersibility and functionality can be improved. The basic method for converting hydrophilic inorganic fillers into ones with covalently bound organic groups on the surface is silane treatment. Organofunctional silanes are a hybrid material of silanes and have recently attracted a lot of attention for their versatile properties, which offer a wide range of applications. They are ecologically acceptable and are not found in nature; they are mainly synthesized from silica. They are used in the paint industry as adhesion promoters or cross-linking agents that create strong bonds with the upper layers of the coating and as surface hydrophobizers. The samples were characterized by contact angle and surface energy measurements, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The results of the contact angle analysis indicate that the hydrophobization of the surface has occurred. DSC analysis determined the glass transition temperatures, and TGA analysis determined the decrease in thermal stability of the composite. The FTIR results confirmed the successful modification of the silica surface.