Performance And Structure Design Of Silica Sol/Self-crosslinking Polyurethane-polyacrylate

Waterborne polyurethane(WPU) coating is the direction of the industry development. However, there are also some disadvantages, such as water resistance, solvent resistance and abrasion resistance of WPU material. Various modified methods were used to improve the performance by the researchers.The chemical modified with WPU can significantly solve these problems. The WPU was been modified by three modification of modified silica sol, acrylate and ketone hydrazine. This article innovation comes from the silica sol which was modified by GMA containing unsaturated double bond. It is helpful to introduced it into the WPU molecular chain in the subsequent reaction and the modification from the acrylate and ketone hydrazine. the modified organic-inorganic three-dimensional interpenetrating network structure of the WPU latex film was prepared by means of soap-free in situ emulsion polymerization. The reaction condition and the performance of GMA modified silica sol were studied in this paper. On this basis, the impact of the emulsion and film properties of modified WPU was studied by the content of GMA and modified silica sol. Finally, the microstructure and film-forming performance of self-crosslinking films was discussed because of the effect of ketone hydrazine.The main content of this paper as follows:(1) Three different pH value of nano silica sol was selected to modify in the modification of nano silica sol and a series of modified silica sol relying on different content GMA was prepared.The stability, the particle size and the PDI of the silica sol was investigated by the different pH value, reaction temperature and the content of GMA. Analysis results of IR spectra and microstructure showed modified agent of GMA and the surface of silica sol was combined with the form of chemical compound. the best stability and the minimum size of61 nm was the neutral silica sol when the reaction temperature was 60℃. The size and PDI of modified silica sol decreased at first and then increased alongwith the increasing of the content of GMA.When the content of modifier of GMA was less than 2.5%, the modified silica sol can be stored for 3 months or more at the room temperature.(2) A series of different R value of self-crosslinking WSPUA was prepared in the silica sol/polyurethane-polyacrylate(self-crosslinking WSPUA) and the impact of R value from the film properties was studied. IR spectra showed that the silica sol and ketone hydrazine was successfully introduced into the molecular chain of the polyurethane-polyacrylate. TEM showed that self-crosslinking WSPUA emulsion was spherical, uniform size and not significant core-shell structure. Different R value has obviously influence for the emulsion and the film properties. when the R value increased, the colour of emulsion become gradually from Micro blue semi-permeable to milky white,the mechan- ical stability decreased, pencil hardness and adhesion improved significantly. In addition, the emulsion particle size was also showed a trend of increase as increasing of R value.(3) A series of different content of GMA of modified silica sol of self-crosslinking WSPUA was prepared and the impact of GMA from the film properties was studied. With the rising of the content GMA, the colour of emulsion become gradually from Micro blue semi-permeable to milky white,size increased, the mechanical stability decreased, pencil hardness and adhesion improved significantly. The water absorption, tensile strength, surface smoothness and heat resistance of self- crosslinking WSPUA were significant increased along with the increase of GMA content.(4) A series of different content of modified silica sol of self- crosslinking WSPUA was prepared and the impact of modified silica sol from the film properties was studied. With the rising of the content modified silica sol, the colour of emulsion become gradually from Micro blue semi-permeable to milky white, the mechanical stability decreased, the size decreased at first then increased, the minimum size was 60.63 nm. When the content of silica sol increased to 9%, the 10% thermal decomposition temperature of latex film was increased to 250.9 ℃, the tensile strength was increased to 16.12 MPa, the Ra was reduced to 1.15 nm and water absorption and breaking elongation rate was decreased obviously. When the content of silica sol reached 12%, theseperformance of latex film was no longer apparent improvements with 9%.(5) A series of different proportion Ketone hydrazine of modified silica sol of self-crosslinking WSPUA was prepared, The effects of the Surface morphology, thermal stability, water resistance, tensile properties, SEM and the coating performance of different proportion ketone hydrazine of self-crosslinking WSPUA was studied. The increasing of the content of crosslinking agent ADH, latex film was becoming more and more smooth and the thermal stability, water resistance and tensile properties of WSPUA were significantly improved as crosslinking agent of ADH increasing and ketone hydrazine percentage declining. The pencil hardness was improved from H to 3H and adhesion and impact resistance was significantly increased coating performance of WSPUA.