Preparation And Properties Of Acrylate-polyurethane Modified By Nanofillers Via Miniemulsion Polymerization

In recent years, in order to combine polyurethane (PU) excellent wear resistance, higher tensile strength and impact strength with the acrylic resin (PA) good water resistance and adhesion, low-cost requirements of water-based resin, PUA composite emulsion known as the third generation of polyurethane has received the widespread attention. With the development of waterbased polymer, further exploiting high performance and multi-purpose materials become more and more popular with researchers both domestic and abroad. Appling nanometer inorganic particle to waterborne polymer, on the one hand, it may improve their traditional performance; On the other hand, it may endow them with new functions. Because of inorganic particles'small size, it isn't stabile in the polymerization process and the traditional emulsion polymerization cann't produce nanocomposite particles with great encapsulation efficiencies of inorganic particles.However, miniemulsion polymerization is different with the conventional emulsion polymerization. In the miniemulsion polymerization techniques, the inorganic particles are dispersed in the monomer phase followed by minemulsification, each submicron droplet act as a nanoreactor, which produce nanocomposite particles with great encapsulation efficiencies of inorganic particles. Therefore, miniemulsion polymerization is a powerful tool in preparing nanocomposite particles.In this paper, we synthesized a series of TiO2/P(MMA-BA), SiO2/P(MMA-BA) and SiO2/acrylate/polyurethane nanocomposite particles. All the research contents and results are as follows:In the second section of the dissertation, nano-TiO2 particles was modified by 3-(trimethoxysilyl)propyl meth-acrylate(MPS), and further the core-shell composite particles was preparation via miniemul-sion polymerization. Thermogravimetric analysis (TG) characterization showed the encasulation efficiency of nano-TiO2 was about 9.13%-10.06% with the MPS; and the relationships of the amount of emulsifier, stabilizer and the conversion were discussed,the results showed that the temperature should be controlled at 70℃, when the content of emulsifier was 2% of the monomer and costabilizer(HD) was 3%, the particles can be stable with narrow particle size distribution; Besides, the water-absorbing ratio, pull extensor strength and TG tests showed that nano-TiO2 can increase the water resistance, weather resistance and tensile strength of the poly-mer.In the third section of the dissertation, polymer/SiO2 nanocomposite particles were prepared by the double in situ miniemulsion polymerization method in the presence of surfactant (sodium dodecyl sulfate), costabilizer (hexadecane), methyl methacrylate (MMA), butyl acrylate (BA), and silica precursors (tetraethoxysilane, TEOS). The formation of SiO2 particles and the polymerization of organic monomers took place simultaneously. A silane coupling agent, y-methacryloxy (propyl) trimethoxysilane (MPS), was used as a functional comonomer to chemically link the polymer and inorganic silica via the copolymerization of MPS, MMA, and BA. The morphology of nanocomposite particles was characterized by transmission electron microscopy (TEM). The microstructure, mechanical properties, thermal properties, and optical properties of the as-prepared films were characterized by scanning electron microscopy (SEM), materials testing machine, thermogravimetric analysis (TGA), and UV-vis spectroscopy, respectively. The results showed that the P(MMA-BA)/SiO2 nanocomposite particles had a raspberry-like structure with nano-silica chemically adsorbed onto the polymer microspheres. The ultrafine silica particles of about 20 nm were highly dispersed within the nanocomposite films and the transmittance of the nanocomposite film was comparable to that of the copolymer latex film at around 70-80% from 400 to 800 nm. The mechanical properties and the fire retardant behavior of the polymer matrix were improved by the incorporation of nano-silica.In the fouth section of the dissertation, first, The polyurethane(PU) prepolymer was prepared by condensation of isophorone diisocyanate and polyethylene glycol using 1,4-butanediol as a chain extender and hydroxyethylacrylate or ethanol as end-capping reagents. The polyurethane-acrylate hybrid nanoparticles were obtained via miniemulsion polymerization. The FTIR and 1H-NMR spectra of these purified hybrid samples were obtained. The scanning electron microscopy(SEM) and Transmission electron microscopy(TEM) pictures of polyurethane/acrylic hybrid were also discussed. The result showed that PU can be used as the costabilizer, and polymerization rate and conversion dropped with the concentration and molecular weight of polyurethane increasing. Besides, stable emulsions can be prepared when the miniemulsification time was 5 minutes and rotational speed was above 14000rpm. what's more, narrow diameter distribution of PUA hybrid nanoparticles was obtained with oil-soluble initiator initiating. And the cross-linked polyurethane-acrylate hybrid containing PU with the acrylic endgroup was obtained during miniemulsion polymerization.In the fifth section of the dissertation, SiO2/acrylate/polyurethane nanocomposite particles were prepared via two different kinds of miniemulsion polymerization methods. One is to make inorganic particles well dispersed in the monomer phase. The other is to use silica precursors(TEOS), and the formation of SiO2 particles and the polymerization of organic monomers took place simultaneously. This article researched the preparation and modification of nano-SiO2, effect of SiO2 on the mechanical properties and thermal stability of nanocomposite films and TEOS content on the stability of miniemulsion polymerization. The FT-IR spectra, tensile stress-strain, water-absorbing ratio, thermogravimetric analysis(TGA) and the scanning electron microscopy(SEM) of SiO2/acrylate/polyurethane nanocompo site were obtained. The result showed that the second method is facile and efficient, and nanocomposites with silica particles highly dispersed within the films were obtained through the double in situ miniemulsion polymerization. The mechanical properties and water resistance of the polymer matrix were improved by the incorporation of nano-silica. But the stability of miniemulsion polymerization reduced gradually with increasing the content of TEOS.