Mechanical Behaviour of Hybrid SiO2-PMMA Coatings Measured By Nanoindentation

by J.L. Almaral-Sanchez AZojomo, 2 May 2006 Hybrid coatings of silica-polymethylmethacrylate were prepared by a modified sol-gel process using different molar relationships for TEOS:polymethylmethacrylate and constant quantities of 3-methacryloxypropyl-trimethoxysilane as bonding agent, for all the samples. Coatings were deposited on glass substrates by the dip coating method. The hybrid coatings were studied by Fourier transform infrared spectroscopy and by two different depth sensing indentation systems. Infrared spectroscopy measurements clearly showed the formation of the hybrid material. The effective hardness of the coatings was analyzed using the work of indentation model. From the indentation measurements we found that the mechanical properties of the hybrid coatings were improved in comparison with those of conventional acrylics. Hardness of the hybrid coatings was from three times to more than one order of magnitude higher than the acrylic hardness, depending on the molar ratio. An extra hardening phenomenon was measured at the surface of the coatings, which is probably due to an enrichment of silica at this region. Finally we found that hardness of the coatings decreases monotonically with the polymethylmethacrylate content. These results allow us to prepare hybrid coatings with tailored mechanical properties. Read more