Preparation Of Nano TiO₂ Composite Emulsion Coatings

Waterborne coatings possessed of many advantages such as low VOC content non-toxic, nonflammable, environmental-friendly etc, at the present time waterborne coatings not provide excellent properties compared to conventional solventborne coatings, water resistance and hardness of the paint films was not half so wonderful as solventborne coatings. Inorganic nano-particles can be successfully addition to resins, which preparation of nano composite waterborne coatings is one of the best solutions. Nano TiO2 is a unique photocatalytic inorganic material, which can be prepared self-cleaning and anti-UV functional coatings, so the research has great significance to prepare nano TiO2 composite coatings. Nano TiO2 exhibit unique optical properties because of the small sizes, large specific surface characteristics and the aggregative trend, these factors affecting the dispersivity of nano TiO2 in polymer, surface modification for nano TiO2 which is the key to successful nano composite waterborne coatings.In this paper the main contents were as follows:(1) Used diphenylmethane diisocyanate (MDI) react with nano TiO2,-NCO groups grafting on the surface of nano TiO2 react with compounds containing hydroxyl(PPG, Diethylene glycol, DMPA), nano TiO2 connected to polyurethane chains by react with -NCO, successfully prepared good store stability core-shell type nano TiO2 polyurethane composite emulsion.(2) Modification of nano TiO2 Surface by the same way react with MDI,-NCO groups grafting on the surface of nano TiO2 react with PPG, Diethylene glycol, DMPA and E51, nano TiO2 connected to epoxy-polyurethane chains by react with-NCO, and successfully prepared good store stability core-shell type nano TiO2 epoxy- polyurethane composite emulsion.(3) Developed a new method of obtaining nano TiO2 modified with oleic acid (OA) by only one step, and then preparation of nano TiO2 styrene-acrylic composite emulsion via semi-continuous emulsion polymerization. Investigates the effect produced by the addition of nano TiO2 to the polyurethane films, epoxy-polyurethane films and styrene-acrylic films, the effect produced by epoxy resins to the polyurethane. The mechanical properties of composite films, the UV absorption, the appearance and store stability of the composite emulsion were researched. The results indicated that proper quantities nano TiO2 improve water resistance and thermal stability of the composite films, the hardness graded of 0.6 wt% nano TiO2 composite films can reach to H, the maximum tensile strength of styrene-acrylic composite films can reach 12.3 MPa, nano TiO2 epoxy-polyurethane composite emulsion and nano TiO2 styrene-acrylic composite emulsion have wide field of application with good prospects.