The Research Of Oligomer Functionalized Nano-silica And Its Application In UV-curing Polyurethane Nanocomposites

The silica nanoparticles have attracted substantial attention owing to their enhanced physical and chemical properties including high hardness, relatively low efractive index, good chemical stability and scratch and abrasion resistance. However, the silica nanoparticles are tend to aggregation because of the increment in the surface silanol structure and high surface energy, which are detrimental to industrial applications. To improve the dispersibility and compatibility of nanosilica within the polymer matrix and to yield a better mechanical and some surface properties, in this thesis, we proposed a new method to functionalize the silica with three types of oligomer(polymer) based polyurethane via amine-isocyanate coupling reaction, The PU nanocomposite films were prepared with the incorporation of treated silica through the covalent or hydrogen bonding interaction between the oligomer onto the surface of silica and PU chains. The main work have been divided in the following three aspects:Firstly, a photosensitive polyurethane was grafted onto the surface of silica particles. IR and TGA results confirmed the existence of PU oligomer at the surface of silica.The PUA nanocomposite films were prepared with the incorporation of the surface treated silica. The SEM analysis showed that small PU-SiO2clusters were homogeneously dispersed in PUA matrix. The grafted PU chains enhanced interfacial interaction and compatibility between silica and PUA matrix, which are further proved by rheological behavior and DMA analysis. The PU-SiO2functionalized nanocomposite films displayed enhanced Young’s modulus, storage modulus and tensile strength compared with the bare silica and silica modified with the silane coupling agents.An amphiphilic random acrylate copolymer was synthesized, and then the copolymer was grafted onto the surface of silica particles, The nanocomposite films were prepared with the incorporation of the surface treated silica, the TEM analysis showed that copolymer-silica uniformly dispersed in both non-polar and polar solvents, SEM analysis showed that copolymer-SiO2clusters homogeneously dispersed in WPU matrix. Stress-strain analysis, TGA demonstrated that copolymer-SiO2functionalized nanocomposite films displayed better tensile strength (2.4times), Young’s modulus (6.6times), elongation (1.16times), thermal stability than the WPU films.A photosensitive coumarin-polyurethane oligomer was grafted onto the surface of silica nanoparticles via amine-isocyanate coupling reactions. The morphology of treated silica nanoparticles dispersed in different organic solvents and polyurethane matrix was observed by TEM and SEM under UV-light conditions with different wavelength. It was found that the coumarin-SiO2clusters were all homogeneously dispersed in WPU matrix and did not aggregate seriously, which had been proved by the SEM analysis. Rheology and stress-strain analysis demonstrated that the evidence of stronger interfacial interactions resulting from the reversible photodimerization of two coumarin molecules. In compared to bare silica and silica modified with the silane APTES, the coumarin-SiO2functionalized nanocomposite films displayed enhanced Young’s modulus(47.8Mpa), tensile strength(47.8Mpa), and elongation(265%), the nanocomposite films exhibited high transparency (transmittance above80%) and well thermal stability.The contrast experiment proved that the evidence of stronger interfacial interactions between two coumarin molecules, the PU nanocomposite films exhibited improved tensile strength upon UV irradiation at λ>300nm.