Scratch Resistant Sol-Gel based Nanocomposite Films on Polycarbonate: DMTA, Small Angle X-ray Scattering and FTIR Studies

Organic-inorganic hybrid materials are the most attractive compounds for coatings due to the combined properties of organic polymers such as processability, flexibility, low density and those of inorganic materials such as thermal stability and high hardness. The properties of nanocomposites are dependent on the size and shape of dispersed phase as well as interaction of two phases. Compatibility and interaction of two phases govern optical and mechanical properties. Inorganic nanoparticles can be dispersed in organic matrix physically. Alternatively they can be connected to the matrix with strong bonds. In the mean time connection of two phases with covalent bond is the most favorable method. In sol-gel process a network former such as tetraethyl orthosilicate (TEOS) take apart in the hydrolysis and condensation reactions and form inorganic network. An organoalkoxide can play the role of coupling agent and connect inorganic network to the organic one. Sol-gel type hybrid coatings provide several advantages such as : i) low temperature synthesis while yielding highly pure homogenous metal oxide materials., ii) low toxic solvent is used iii) desirable size and shapes can be obtained and iv) it is possible to have coating with high inorganic content.Polycarbonate is a thermoplastic engineering polymer that has good properties such as high transparency, low density and high toughness. But low hardness causes PC to lose transparency when scratched. In plastic coating such as polycarbonate increasing of temperature higher than Tg leads to curvature. Therefore, UV curable organic resins can be a good alternative. UV curable resins such as urethaneacrylate can create properties of organic coatings such as flexibility and barrier properties. The energy of UV irradiation can cure organic part and in the same time condense the sol-gel part.The aim of this work is the study of the role of coupling agents on the structure and morphology of silica phase. The effect of this morphology on the mechanical properties of hybrid coatings used for PC has been discussed.

کلیدواژه ها:

Sol-gel ، Nanocomposite ، Polycarbonate ، Hybrids