Preparation And Modification Of Aqueous Polyurethane Emulsion

Aqueous polyurethane (aqueous PU) is dispersed in water media, which has not only the excellent properties of solvent-borne polyurethane with low temperature resistance, great adhesion, as well as outstanding toughness combined with good flexibility, but also advantages of incombustibility, low odor and environmental [iLndliiiess that solvent-borne adhesive has not. Therefore, emphasis on it was paid by researchers home and aboard. Aqueous PU adhesive has been made a great progress in many other countries, but domestic research on it was limited by sorts of conditions, which is basically in primitive stage. In this paper we aimed at the preparation of aqueous PU emulsion and the analysis on the properties and factors, the modification based on it, and so as to acquire modified aqueous PU with excellent properties. Aqueous polyether PU emulsion and aqueous polyester PU emulsion were prepared by prepolymer mixing process and aceyone process. The effects of change of dimethylolpropionic acid (DMPA) content and R (nNCJnOH ) value on the properties of emulsion and adhesive were researched. The results show that the change of DMPA content and R has effects on appearance, viscosity, particle size, stability and solidification velocity. The change of R has also effects on hygroscopicity, thermodynamic stability, glass transition temperature and mechanical strength. The effects of change of DMPA content and R on adhesion power such as cutting strength and peeling strength are complicated by sample quality, humidity, solidification time and so on. Based on polyether aqueous PU, aqueous polyurethane and acrylic copolymer emulsion (PUA emulsion) with core-shell structure were prepared by the modification of acrylate. The effects of proportion of acrylate and PU (A/PU) on emulsion and adhesion were studied. The results show that the change of A/PU influences emulsion characteristics such as particle shape, particle size and cutting strength, and the properties of emulsion-cast like hygroscopicity, solvent resistance, mechanism, thermodynamic stability and glass transition temperature. Compared with PU emulsion, acrylate emulsion (PA emulsion) and mixed emulsion of PU and PA, properties of PUA emulsion are better than those of mixed emulsion of PU and PA, not say PA emulsion and PU emulsion.