A study on poly(tetrafluoroethylene) (PTFE) reinforced with tetraethoxysilanes (TEOS) derived SiO2 is described. It included the manufacturing process of SiO2-reinforced PTFE and the effects of silylation agent on the properties of the hybrid material, such as porosity, hydrophobic, thermal resistance, dielectric and mechanical properties, and microstructure. PTFE/SiO2 hybrids of 50 wt % SiO2 loading were prepared via a sol-gel process and were shaped by a two-roll milling machine. Trimethylchlorosilane and hexamethydisilazane were used as the silylation agents. Our results showed that the water absorption and dielectric loss of PTFE/SiO2 hybrid had significantly improved with silylation agent. The silylation process replaced Si-OH with Si-CH3 on the surface of the TEOS-derived silica colloidal particle. The existence of trimethylsilyl [-Si(CH3)(3)] on the surface of the modified PTFE/SiO2 hybrid was confirmed via infrared and solid-state Si-29 magic-angle spinning nuclear magnetic resonance spectra. Nitrogen-sorption techniques were used to characterize the modified and unmodified PTFE/SiO2 hybrids. The microstructure of SiO2 in the matrix was also evaluated with scanning electron microscopy and transmission electron microscopy. Our results showed that the silylated sol-gel-derived PTFE/SiO2 hybrids had exhibited high porosity (53.7%) with nanosize pores (10-40 nm) and nanosize colloidal particles (20-50 nm). This manifests itself as have the ultralow dielectric properties (D-k = 1.9 and D-f = 0.0021), low coefficient of thermal expansion (66.5 ppm/degreesC), high tensile modulus (141 MPa), excellent thermal resistance (T-d = 612 degreesC), and an increased hydrophobia (theta = 114degrees); moreover, the hydrophobic property of the PTFE/SiO2 hybrid was thermally stable up to 400 degreesC. (C) 2004 Wiley Periodicals, Inc.