Characterization of colloidal particles formed in plastic coating solution at room temperature

The structure of solution of methyltrimethoxysilane (MTMS), which is used for hard coating for plastic materials through its sol–gel reactions, was investigated by light scattering, atomic force microscopy, infrared spectroscopy, and X-ray diffraction. Although hard films can be formed only after heating the MTMS solution and no significant increase in viscosity can be found at room temperature, colloidal particles were detected in the solution by light scattering immediately after adding the catalyst. Particles with a size comparable to that determined by light scattering were observed by atomic force microscopy. The change induced by the growth of the particles was measured for 4 weeks. The infrared spectroscopy and X-ray diffraction for the solutions changed gradually, which supports the formation and growth of the colloidal particles. These results indicate a very slow reaction of MTMS and structural change in the solution even at room temperature, which can affect successful coating of plastic materials using MTMS.