Dış Cephe Boyalarında UV Dayanımının Arttırılması İçin Yeni Nesil Çinko Oksit Bazlı Nano Katkıların ve Hibrid Bağlayıcıların Geliştirilmesi
Eren , Mesut
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Along with technological development of paint industry, the quality and durability expectations the final consumers for architectural paints is continiously increasing. Since the profit margin of these paints is low and competition is serious, the manufacturers are continuously researching for additives which shall provide improvement with reasonable cost. Nano zinc oxide is accepted to be among recent popular additives on trial, due to its low cost, known UV absorption capacity and is considered to be non toxic in comparison with other paint components. In this work, semi-batch seed or monomer starved emulsion polymerization of methyl methacrylate-butyl acrylate containing either methacrylic acid or acrylamide or benzophenone methacrylate/methacrylic acid co-monomers were carried out to prepare binders for exterior architectural paints. During polymerization, unmodified powder or water dispersed nano zinc oxides or hydrophilic or hydrophobic silane modified nano zinc oxides were added to monomer feed to prepapare different types of nano zinc oxide hybrids. In case of addition of methacrylic acid containing co-monomers nano ZnO reacted with acid groups to form zinc methacrylate or dimethacrylate which participated in crosslinking reactions. The amount of nano ZnO added was increased up to the equivalence point and in several cases exceeded for unmodified or modified nano zinc oxides. The emulsions and clear polymer films obtained from them were characterized with conventional methods. FTIR and UV-Vis spectra confirmed the transformation of nano zinc oxide to zinc methacrylates up to the equivalence point. The emulsions were used for preparing of opaque and transparent base paints. These base paints were tinted with a red pigment paste and colored paints were obtained. The paints and clear polymer films obtained from emulsions were subjected to UV exposure-condensation accelerated weathering test The color parameters, gloss and water contact angle changes were determined for every 250 hours up to 1000 hours. Optical microscopy and for some cases AFM and FTIR were also used for further characterizations. Presence of zinc methacrylate cross linking and in some cases, additional presence of nano ZnO, provided blistering prevention and significant improvement of gloss and color stability.
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