Preparation And Characterization Of Nano-TiO₂ /acrylate Composite Emulsion

Nanocomposite materials have received significant attention in recent years for their special properties. Nano-titanium dioxide (TiO₂) not only has small size effect, surface and interface effect, quantum dimension effect and macroscopic quantum tunnel effect like the ordinary organic nanometer particles, but also has the special functions such as ultraviolet radiation shield effect, photocatalysis effect, etc, and are widely studied to be used in medical science, textile, paint, etc.Acrylate paint is extensively applied in many fields. The mechanical properties and weatherability of acrylate will be improved if nano-titanium dioxide applied in the polymerization of acrylate emulsion.In this paper, nano-titanium dioxide (nano-TiO₂) was prepared by sol-gel method, using butyl titanate (TBOT) as precursor, hydrochloric acid (HCl) as catalyst andγ-methacryloxypropyl trimethoxy silane (KH-570) as modifying agent. Nano-TiO₂/ acrylate composite emulsion was prepared by emulsion polymerization using organic nano-titanium dioxide sol, methyl methacrylate (MMA), butyl acrylate (BA) and acrylic acid (AA).The main content and the results of this paper are as follows:Firstly, the effects of the content of ethanol, HCl and KH-570 on the surface modification of nano TiO₂ were studied. The structure of nano-TiO₂ was characterized by FT-IR and XRD. The results showed that KH-570 was grafted onto the surface of nano-TiO₂ particles by means of chemical bonds and the crystal form of nano-TiO₂ was anatase form. Compared with the unmodified nano-TiO₂, the lipophilicity of KH-570 modified nano-TiO₂ was improved obviously. With the increase of HCl content, the crystallization degree of nano-TiO₂ was enhanced. The content of KH-570, ethanol and HCl also had an effect on the grafting ratio and particle size of nano-TiO₂ sol. When nKH-570/nTBOT=0.2(mol ratio), nEtOH/nTBOT =6, nH2O/nTBOT =1, nHCl/nTBOT =0.48, the grafting ratio reached 25.6%, the minimum value of particle size was10.0nm and particle size distribution was the narrowest.Secondly, the effects of the content of monomer, emulsifier, initiator and organic nano-TiO₂ sol on the polymerization reaction were discussed.The emulsion was characterized by TEM and particle size analyzer. The results showed that the compatibility between nano-TiO₂ and polymer was good. With the increase of nano-TiO₂ sol content, the particle size of latex increased. When the content of AA, initiator, emulsifier and nano-TiO₂ sol were 3wt%, 0.6wt%, 3wt% and 2wt% separately, the minimum value of gel ratio was 0.87% and the conversion was 97.8%.Thirdly, the effects of pre-emulsifying method, the content of monomer, emulsifier, initiator and organic nano-TiO₂ sol on the properties of latex film were discussed.The latex film was characterized by TG. The results showed that the effect of nano-TiO₂ sol on the adhesion and flexibility of latex film was little, but the impact property, pencil hardness, ultraviolet resistance and heat endurance were improved. The content of AA, initiator and emulsifier also had an effect on the properties of latex film. When the content of AA, initiator, emulsifier and nano-TiO₂ sol were 5wt%, 0.5wt%, 3wt% and 2wt% separately, the comprehensive properties of latex film were the best, the water absorption, adhesion, pencil hardness, impact property, flexibility and glossiness were 13.9%, 0-1 grade, H-2H, 55cm, 2mm and 125.0% separately.