|
The aqueous polyurethane and composite nanoparticles can improve the water solvent resistance and mechanical properties of waterborne polyurethane given the polyurethane material UV shield, absorbing, conductive, thermal insulation, wear and other functions. The introduction of water-based polyurethane nano-SiO 2 generated in situ method, sol - gel method and direct mixing method. But the in situ generation method using a greater limitations, is only suitable for containing a solution of metal, sulfide or hydroxide colloidal particles, the monomer molecules in situ polymerization Preparation of nano-coatings. Most of the sol - gel method using the precursor is alkyl silicate vinegar, expensive, toxic, and easy in the course of the reaction by the pH, solvents, catalysts, and the influence of temperature; but also during the drying process, since the solvent and small molecules volatile, shrinkage stresses inside the material, resulting in material embrittlement, so it is difficult to obtain a large area or thick nanocomposite coating. Direct mixing process is simple, intuitive and economical; However, due to the extremely small nanoparticles, large surface area, nanoparticles can easily gathered into a group, and PU elastomer is a polar polymer, nanopowder affinity is poor, resulting in dispersed bad, the content of the composite nanoparticles is lower, so the improvement of the performance of the aqueous polyurethane is limited. In this paper, three methods nano-SiO 2 introduced into the polyurethane diols dispersed polymer dispersant and surface modified graft law. (1) diol dispersion method is nano-SiO 2 pre-dispersed macromolecular diols of polyurethane raw materials and nano-SiO 2 dispersed in pre-mers, respectively prepared by two methods SiO 2 the same content of water-based polyurethane / nano-SiO 2 composite emulsion, and the performance of the two emulsions test. Simultaneously of the two methods to obtain a composite film the mechanical properties, thermal stability, ultraviolet absorption, as well as the dispersibility of the nanoparticles in the composite film were compared. (2) by adding nano silica acetone solution to the polyurethane prepolymer, the emulsification dispersant polyacrylic acid sodium salt of the polymer electrolyte is added to isophorone diisocyanate (IPDI), polytetrahydrofuran ethers two alcohol, 2,2 - bis (hydroxymethyl) propionic acid, 1,4 - butanediol as the main raw material, the law, prepared by the self-emulsifying SiO 2 IPDI different levels of water-based polyurethane / silicon oxide composite (PU / SiO 2 ). Fourier transform infrared spectroscopy analysis confirmed the PU / SiO 2 structure. The mechanical properties of the composite membrane at the same time, thermal stability, UV absorption and dispersion of the nanoparticles in the composite film were analyzed. (3) γ-aminopropyl triethoxysilane (KH550) surface-modified nano-silica, so that the nano-SiO 2 the surface with a reactive amino; then with NCO-terminated urethane reaction, by a method of graft nano - SiO 2 is introduced into the polyurethane molecule chain. Finally, the use of Fourier transform infrared and scanning electron microscopy to characterize, and film performance analysis papers.
|