Preparation And Properties Of UV-curing Polyurethane Acrylate Matting Material

In recent years,matting coatings has been widely demanded in the market because of their natural elegance,in line with modern aesthetic and can reduce light environmental pollution.Silica（SiO₂）has become a common inorganic matting agent in high-grade coatings due to its chemical inertness,controllable particle sizes,and similar refractive index to firm forming resins.In the process of coating synthesis,UV-curing polyurethane acrylate（PUA）coatings have the advantages of high impact strength,wear resistance and elongation at break,so they are popular applied in the industrial coatings,textiles,links and other manufacturing industries.The UV-curing coatings combine the advantages of inorganic particle and UV-curing technology,so as to obtain matting organic/inorganic composites with excellent performance.However,the high surface activity and hydroxyl groups with different bond states of silica,which are prone to conglomerate in the UV-curing coatings,resulting the poor matting and poor comprehensive performance of the composites.In order to address these problems,SiO₂was modified by three different methods to graft high-molecular polymer and organics onto the surface of SiO₂to improve the dispersion of SiO₂in the PUA coatings.A series of UV-curing coatings were prepared empolying modified SiO₂and PUA coatings,and the matting property,thermal stability and wear resistance of the composites were studied deeply.The main research contents are as follows:1.The condensation reaction of isophorone diisocyanate（IPDI）with the hydroxyl groups on the surface of the SiO₂particles was carried out,and the end capping was completed with hydroxyethyl methacrylate（HEMA）to obtain modified SiO₂with surface grafted polymer.The modified SiO₂was added into PUA UV-curing coatings to prepare modified SiO₂/PUA composites containing different SiO₂particle sizes.The results showed that the smaller the particle sizes of the added modified SiO₂,the lower the glossiness and the stronger the hydrophilicity of the composites.Meanwhile,the adhesion and wear resistance of the composites material were superior to the UV-PUA.As the the average particle size(D₅₀)of SiO₂was 2.5μm and the loading was 1.40 wt%,compared with the pure UV-PUA material,the surface glossiness（60°）of PUA/modified SiO₂composites was decreased 14.1,the adhesion grade was enhanced to 0,and the wear weight loss rate and the water contact angle were reduced to 0.05%and 40.2°,respectively.2.SiO₂was pretreated withγ-glycidyl ether oxypropyl trimethoxysilane to introduce epoxy groups onto the surface of the particles,and then the maleic anhydride/hydroxyethyl methacrylate（MAH/HEMA）organic matter was grafted on its surface through the epoxy ring-opening reaction to prepare the organic matter-modified SiO_2.The modified SiO₂and maleic anhydride grafted polyethylene wax（PEW-g-MAH）were added to the UV-curing coatings as the matting agent by physical blending method.Under the synergistic effect of the two, modified SiO₂/PUA composites containing different amounts of PEW-g-MAH were prepared.The results showed that-C=C groups grafted on the surface of SiO₂can react with-C=C groups of PUA coatings to form chemical crosslinking,which improved the dispersion of SiO₂in the polymer system,at the same time,the addition of PEW-g-MAH also further enhanced the dispersion of SiO₂in the coatings.Compared with pure UV-PUA material,when the content of modified SiO₂was 1.30wt%,the surface glossiness（60°）of modified SiO₂/PUA composites decreased to 50.7,and when 1.40 wt%of PEW-g-MAH was added,the surface glossiness（60°）of composites was decreased to 19.5,the adhesion grade was enhanced to 0,the wear weight loss rate was reduced 0.10%and the water contact angle was reduced to 72.2°.3.SiO₂was aminated by 3-aminopropyl triethoxy silane（KH550）,and then epoxy ring-opening reaction with glycidyl methacrylate（GMA）was carried out to obtain the modified SiO₂with activated carbon double bond grafted on the surface.The modified SiO₂was introduced into the methyl ethyl ketoxime（MEKO）modified PUA UV-curing coatings,and the modified SiO₂/PUA composite material containing different MEKO dosages was prepared by the method of UV/thermal dual curing.The results showed that the modified SiO₂can be effectively dispersed in the UV-curing coatings after grafted the organic chain segment,and caused the surface of the composite material to form an uneven film structure.Under the radiation of UV curing machine,the-NCO groups unsealed in the film forming process can form the carbamate bonds with-OH groups in HEMA molecule.The interaction of molecules leaded to the microphase separation on the film surface,which in turn improved the roughness of the film surface.When the modified SiO₂content was 3.50 wt%,the surface glossiness（60°）of the composite material was reduced to 40.8 compared to the pure UV-PUA light-curing material,and when the n（MEKO）/n（NCO）in the UV curable coating was 0.6,the surface glossiness（60°）of the modified SiO₂/PUA composites was reduced to 13.9,the adhesion grade was enhanced to 0,the wear weight loss rate was reduced 0.12%,the shore hardness was enhanced to 96.3 HD and the water contact angle was increased to 97.8°.