Synthesis And Properties Of Nano-ZnO Modified Waterborne Polyurethane Composite Materials

A series of nano-ZnO modified waterborne polyurethane composite latex were synthesized from polyester polyol, isophorne diisocyanate (IPDI), dimethylol propionic acid (DMPA), ethylenediamine (EDA) and nano-ZnO which were modified by silane coupling agent by anionic self-emulsified method. The structure of nano-ZnO before and after the modification and the polyurethane/modified nano-ZnO composite films were characterized by fourier transform infrared spectroscope (FTIR). The conditions of surface modification of nano-ZnO have been studied, including the types and amount of silane coupling agent, reaction temperature and time. The effects of the molar ratio of NCO/OH, the amount of DMPA, the content of nano-ZnO on the basic properties such as particle size and emulsion viscosity of composite emulsion, and water resistance and tensile properties of the composite films werde discussed. Meanwhile, the influences of the content of nano-ZnO on the friction property as well as pencil hardness and adhesion of the composite coatings were studied.The results showed that the effect of surface modification of nano-ZnO was better when the amount of the silane coupling agent was5wt%, the reaction temperature was70℃, the reaction time was2h. Meanwhile, the composite films exhibited favorable comprehensive properties with the addition of0.5wt%modified nano-ZnO.In the study of the properties of the nano-ZnO modified waterborne polyurethane composite materials, the following research results were obtained. After the modified nano-ZnO was added into the WPU system, the water resistance and tensile properties of the composite materials improved a lot. But the stability of composite emulsion changed little. The increasing of nano-ZnO content resulted in that the particle size kept rising and the viscosity went down for the composite emulsion. At the same time, the water absorption of composite films dropped at first and increased later. The tensile strength and the enlongation at break both increased gradually in the beginning and declined finally. When the content of modified nano-ZnO was0.5wt%, the tensile properties of composite films were the best. The addition of modified nano-ZnO could improve the friction properties effectively. The composite coatings exhibited better abrasion performance with the amount of nano-ZnO of0.5wt%. The pencil hardness and adhesion of the composite coatings have both improved.With the increase of the molar ratio of NCO/OH, the particle size of the polyurethane composite emulsion decreased at first and then increased. However, the viscosity of composite emulsion and the water absorption of composite films showed the opposite law. The tensile strength of the polyurethane composite films enlarged, but the enlongation at break decreased. With increasing the amount of DMPA, the viscosity, the water absorption and the tensile strength of the polyurethane films went up, and the particle size and the enlongation at break declined. The pencil hardness increased while the adhesion had little change.