FST is amorphous fumed silica, produced by vapor phase hydrolysis of Silicon Tetrachl in flame of hydrogen and oxygen, the resulting products are pure, xray amorphous. Silicon Dioxide (SiO2). FST is pure amorphous pyrogenic silica, non-toxic and is not flammable or combustible. Its original particle size is between 7-40 nm, it has high surface activity. It can be widely used as reinforcing, thickening, thixotropic, matting, defoaming UV sterilization etc.