Preparation Of Scratch Resistant Organic-inorganic Hybrid Nanomaterials By In-situ Photopolymerization Technology

Organic-inorganic hybrid materials have drawn tremendous attention among the academic and industrial scientific communities because they combine advantages of inorganic and organic materials. Usually, most organic-inorganic hybrid materials are thermally cured, but some of them are cured by UV light. UV cured hybrid materials field is very promising because it combines the advantages of traditional hybrid materials and UV-curing technique, mainly including high-speed process, lower energy consumption as well as the curing process occurs at ambient temperature, lower process costs, high chemical stability of materials and lower VOCs (volatile organic compounds) of UV-curing technique, and the improvement of thermal and mechanical properties etc., due to micro-scale homogeneous network of the organic-inorganic hybrid material.Polymer coatings have been largely employed as possibilities for many protective and aesthetic applications. Consequently, in addition to bulk properties also surface properties, such as resistance to indentation and scratching, are critical to retain the basic coating functions. There are two main ways to improve the scratch resistance of organic coatings:one is to optimize the polymer lacquer components and the other is to reinforce the coating by embedding fillers into them. Accordingly, in this study, we prepared a series of silica sols to enhance scratch resistance properties of polymer coatings by sol-gel method, including nanosilica/acrylate hybrid oligomer containing tertiary amine moiety and UV curable MPTMS/SiO2sols.(1) Nanosilica/acrylate hybrid oligomer (HAP-GMA sol) containing tertiary amine moiety was prepared by sol-gel method of the product (AP-GMA) synthesized from3-Aminopropyltriethoxysilane (APTS) and glycidyl methacrylate (GMA). Using mainly transmission realtime Fourier transformed infrared (RT-FTIR) spectroscopy to characterize UV curing behavior of AP-GMA, HAP-GMA sol, AP-GMA coating and HAP-GMA hybrid coating. Excellent scratch resistant and thermal stability of HAP-GMA hybrid coating with respect to pure UV-cured organic coating (AP-GMA coating) were well evident because of micro-scale homogeneous network as well as the interfacial interaction between inorganic phase and the organic matrix. (2) A series of UV curable MPTMS/SiO2sols were prepared based on two-step sol-gel reactions using the different mole ratio of y-methacrylate propyl trimethoxysilicate (MPTMS) and tetraethoxysilane (TEOS), and then the blend of HDDA-TMPTA and the sols which was distilled under several vacuum distillation conditions to form the silica sol/HDDA-TMPTA dispersions. The method to improve the stability of the sol and the sol/TPGDA dispersions after the vacuum distillation was discussed. The silica sol/HDDA-TMPTA dispersions were mixed with the UV-curable organic composition (epoxy acrylate oligomer (EA) and Irgacure184photoinitiator) forming the UV-curing organic-inorganic hybrid coatings.(C=C) double bond conversions of the hybrid system were lower than that of pure UV-cured organic coating. It should be mentioned that the acrylate group of MPTMS may have a lower activity, the absorbing and scattering effects of nanosilica were restricted by the colloidal matrix. It was also observed that the thermal stability and scratch resistant of the hybrids increased with incorporation of MPTMS/SiO2sols into the organic part. UV-cured samples were stored in the dark at an ambient temperature for up to one month. Such storage was found to improve the scratch resistance and to delay the permanent deformation. To further improve the scratch resistance, one could submit the UV-cured coating to a thermal treatment.(3) EA and HAP-GMA sol were used as oligomer, and MPTMS/SiO2sols were used as inorganic components for preparing a series of the UV-curing organic-inorganic hybrid coatings. HAP-GMA sol containing tertiary amine moiety could reduce oxygen inhibition effect and have co-initiator property. Therefore,(C=C) double bond conversions of the hybrid system were slightly higher than that of pure UV-cured organic coating, when incorporation of HAP-GMA sol less than20%into the hybrid coating. It was also observed that the thermal stability of the hybrids did not decrease with decreasing EA content in the hybrid coating.When the hybrid composite materials were heated, nano-silica particles would tend to migration to the surface of the coating film due to their high surface energy, the surface nano-silica played an important role for preventing the degradation of polymer coating film. Acrylated epoxy matrix was a rigid polymer. But the inorganic oligomers HAP-GMA sol obtained by sol-gel method was an opened polyhedron structure which was linked by the organic acrylated chain on the cube edges. This structure was less rigid thanks to the opened structure of the polyhedrons. In this hybrid coatings, incorporation of HAP-GMA sol into the hybrid coating stiffness decreased, the elastic recovery increased. The scratch behaviour of coatings underwent a change from a brittle to a tough deformation. Moreover, the dispersed nanosilica made the polymer more deformable, with an increased elastic recovery and reduced the plastic deformation.