The Preparation Of TiO₂/ZnO Waterborne Polyurethane And The Properties Study

Waterborne polyurethane(WPU) can be dispersed into water to form stable polyurethane emulsions due to the addition of hydrophilic groups and has been widely used in coatings, leathers, textile and other fields because of it has the following advantages, such as its low cost, non-toxic, and friendly to the environment. However, the addition of hydrophilic groups can reduce the water resistance, solvent resistance, resistance to chemical and other properties of the WPU film while improve its dispersion performance. Therefore, organic silicon, organic fluorine, epoxy resin and nanoparticles have been embed in waterborne polyurethane to improve its comprehensive performance. In all of those aforesaid materials, nanoparticles has a great potential in the synthesis of polymer composite due to its surface effect, quantum size effect and their abilities to remarkably improve the properties and performances of the composite. But, it is also because of the huge specific surface area and large surface energy of the particles that make them have strong tendency to generate chemical bond with oxygen in resin, so it is very necessary to modify the surface of the particles before using them.In this work, waterborne polyurethane was prepared from isophorone diisocyanate(IPDI) and polypropylene glycol(PPG-1000)as raw materials, the WPU also was modified by nano-powders of titanium dioxide and zinc oxide.in order to get better polyurethane coatings.Before modified by silane coupling agent KH550, the nano titanium dioxide and zinc oxide were coated by magnesium acetate and ethyl orthosilicate, respectively. Infrared spectrum analysis showed that two-step processing was successful; SEM examination revealed reunite of TiO2 and ZnO powder was improved to some extent by coating with inorganism. While for the hybrid particle mixed with TiO2 and ZnO with the mass ratio of 1:1, oleic acid was chosen as modifier. The results of contact angle and dispersion stability testing showed that the surface hydrophobicity of the nanoparticles was increased and dispersibility in organic medium was enhanced which provided a foundation for modifying WPU emulsion.Then the best modified nanoparticles were chosen to prepare the nanoparticle/waterborne polyurethane composite emulsion by the method of glycol dispersing. Theeffects of r(NCO/OH) value, DMPA content, degree of neutralization and the amount of nanoparticles et al. on the emulsion and the film properties were discussed, and the best formulation of WPU modified by TiO2/ZnO was determined. The IR spectrum chart proved that the nanoparticles/waterborne polyurethane was synthesized successfully; XRD showed that the WPU film modified by nanoparticles were still amorphous; the results of TG showed that to some extent, the addition of nanoparticles could improve the thermal stability of the WPU films; the UV-vis spectrum showed the ultra-violet resistance of nanoparticles/WPU were better than pure WPU films; the results of the electrochemical analysis revealed that the corrosion resistance of the films had been increased by modified.