Enhancement of Fire Retardancy Using Surface-Modified Silica Spheres with Aluminum Hydroxide

Large surface area and fire-inert property of sub-micrometer silica spheres were employed to improve the fire retardant performance by attaching large number of Si–O–Al(OH) _2 groups. Various amounts of AlCl _3 were attached to the surface of silica spheres and the residual –AlCl _2 was hydrolyzed by adding excess amount of KOH. Although the FESEM image of pure silica spheres showed smooth surface, the surface-modified silica spheres exhibited nanoparticles on the surface of silica spheres. The characteristic absorption peaks of Al–OH and Si–O–Al were detected by FTIR spectra. Silica spheres attached with Si–O–Al(OH) _2 were uniformly distributed on the surface of cellulose acetate films. The performance of the fire retardant was greatly enhanced by increasing the amount of aluminum hydroxide.