Synthesis And Characterization Of Silicon Modified Waterborne Polyurethane Coatings

Polyurethane(PU) has been widely used due to its various superiorities. In recent years, Waterborne polyurethane(WPU) is gradually replacing solvent-based polyurethane because of its low volatile organic compounds (VOC) content, low toxicity, good stability, excellent mechanical properties, adhesion resistance, etc.. Nevertheless, due to the introduction of ionic groups, the water resistance and surface hydrophobicity of WPU films is significantly reduced, increasing the water-resistance and hydrophobicity of WPU films while maintaining other excellent properties has high value in its practical applications.Using poly(propylene glycol)(PPG-2000), isophorone diisocyanate (IPDI) as fundamental monomers,2-bis(hydroxymethyl) propionic acid (DMPA) as hydrophilic chain-extender,1,4-butane diol (BDO) and trimethylolpropane (TMP) as chain-extender and cross-linking agent, a series of waterborne polyurethane (WPU) dispersions were prepared through the pre-polymer dispersion process. The extent of reaction under different temperature was tested, the main influencing factors of average particle size and size distribution were discussed, and the water-resistance, hydrophobicity, mechanical properties, thermal resistance property, surface morphology of WPU films after compound modification were researched. The whole thesis included five chapters, which contained:Chapter1:Literature review. The background and the significance of this topic were firstly introduced. Then, the research progress home and abroad, the synthesis method and classification of WPU, the film-forming mechanism were briefly outlined. The common modification methods along with their research progress were discussed in detail. Finally, the research objective and method is raised.Chapter2:Using Di-n-Butylamine-Acetone method to determine the amount of isocyanate groups, the extent of reaction under different temperatures was tested, the optimal production conditions were determined. The effect of various factors on the average particle size and size distribution were discussed. Silane coupling agent was then added to the system during the emulsion process, WPU nano-emulsion with good hydrophobicity and water-resistance of its film was successfully synthesized.Chapter3:Hydroxyl and amino groups could easily react with isocyanato groups on polyurethane, so silane coupling agent, aminosilicone emulsion and hydroxy silicone were used as modifiers of WPU. It was found that by adjusting the component of the modifiers, WPU films with good hydrophobicity and water-resistance can be successfully obtained. Its water contact angle was up to112.4°, while other product properties remained excellent.Chapter4:Hydroxyl silicon oil was added to the system, meanwhile, BDO was replaced by castor oil (CO) in this part. It was found that WPU synthesized in this part had good appearance, stability, and film-forming ability, the modified product with best performance has decreased water swelling, its water contact angle was101.3°, elongation at break was617.0%, tensile strength was12.6MPa, and its thermal stability was improved significantly.Chapter5:conclusions. The research achievements in each part were generalized and the main conclusions were summed up.