Preparation And Surface Modification Of Nano-ZnO And Characteristics Of ZnO/PU Composite Coatings

Nano-materials have a wide range of applications in many industrial fields, andnanocomposites are drew much attention in recent years. Due to their high surfaceenergy and hydrophilic, nanoparticles tend to strongly agglomerate, which seriouslylimits their applications, and degrades the performance of nanocomposites. Therefore,appropriate surface modification of nanoparticles is necessary to enhance thenano-materials. In this study, the preparation and surface modification of nano-ZnOwere carried out, and preparation and characteristics of ZnO/PU nanocompositecoatings were also implemented.In the research, ZnO nanoparticles were produced by direct precipitation methodand coupling grafting surface treatment process was developed to obtain highlydispersed and long-term stabile in organic matrix. In this process,N,N’-carbonyldiimidazole (CDI) was employed as activating agent to promote thecondensation reaction rate between APS and SA. Infrared spectroscopy (IR),sedimentation experiment and scanning electron microscopy (SEM) were employed tocharacter the properties of ZnO nanoparticles. It was found that coupling graftingmodification exhibited the significant effect when stearic acid was activated by CDI,and the modified nano-ZnO particles had a good dispersibility, unform particledistribution and long-term stability in organic solvent. The modifying agent was bondedwith the surface of ZnO nanoparticles and5wt%of stearic acid was the appropriateamount for a better quality of the modified nano-ZnO.Polyurethane resin (PU)/ZnO composite films were prepared by incorporating thedifferent kinds of the modified ZnO nanoparticles into PU matrix and werecharacterized by SEM, TGA and XRD. The interfacial compatility between ZnOnanoparticles and PU matrix was significantly improved by hydrophobically modifyingthe surface of ZnO nanoparticles with APS and activated SA by CDI. It was clearlyfound from SEM observations that CDI-SA-APS-ZnO nanoparticles could behomogeneously dispersed in the PU matrix and had been encapsulated in the PU phase.The properties of ZnO/PU nanocomposites strongly depended on the surface treatmentprocess of nanoparticles and the composite materials by being added withCDI-SA-APS-ZnO nanoparticles exhibited the perfect mechanical and UV-shieldingproperties. It also found that CDI-SA-APS-ZnO/PU nanocomposite coatings have a bettersealing performance and adhesion with the surface of the wood when it was used as thewood primer. CDI-SA-APS-ZnO/PU nanocomposite coatings showed the perfectperformance to the seal the water molecules in the wood and the coatings film had atighter structure, which avoided the blister, shelling and other defects.