Study On High Performance Waterborne Polyurethane Latex

Waterborne polyurethane is a binary colloid system with water as its disperse medium. In this thesis, a series of organosilicon-modified waterborne polyurethane were synthesized with organosilicon, polyether diol, isophorone diisocyanate (IPDI) and dimethylol propionic acid (DMPA) in self-emulsifying process. Effects of the addition methods, the content of organosilicon and DMPA as well as emulsifying temperature were studied on particle size, viscosity, rheology, water absorption and mechanical properties. With an increase of content of organosilicon, the particle size, contact angle of water and pencil hardness increased; the viscosity and elongation at break decreased; the water absorption decreased at first and then increased while the tensile strength was opposite exactly; the test of rheology indicated that the latex was a non-newtonian fluid. With increasing DMPA amount, the particle size, the contact angle of water and elongation at break decreased while the viscosity, water absorption, tensile strength and pencil hardness increased. The water absorption and elongation at break increased, and the viscosity, contact angle of water, tensile strength and adhesion decreased with a higher emulsifying temperature.Meanwhile, a series of composite latex of organosilicon-modified waterborne polyurethane and waterborne polyurethane were prepared. The organosilicon surface enrichment of the composite latex film was investigated by attenuated total reflectance Fourier transform infrared spectroscopy (FTIR-ATR) and atomic force microscopy (AFM). The analysis of FTIR-ATR showed that the content of organosilicon on the air surface was 11.59 times of the one that the contact layer (i.e.glass) contained when the organosilicon content was only 2.14wt%, which indicated that the chain segment of organosilicon was enrichment on the air surface. AFM analysis showed that the topography of the film was improved markedly because of the addition of organosilicon-modified waterborne polyurethane. With the increase of content of organosilicon the contact angle and pencil hardness increased while the water absorption and surface free energy decreased. With an increasing amount of DMPA, the water absorption, surface free energy and pencil hardness decreased but the contact angle increased. The lower the emulsifying temperature is, the larger the contact angle of the film surface is. The surface free energy and water absorption decreased with the emulsifying temperature decreasing.In the research, waterborne polyurethane/poly (n-butyl acrylate-styrene) latex interpenetrating polymer networks (WPU/P(nBA-St) LIPNs) were also prepared by fractional step polymerization. The effects of the component ratio of two networks, the amount of styrene and DMPA on the properties were discussed. With the increasing of P(nBA-St) content the particle size, elongation at break and pencil hardness increased while the viscosity, adhesion and tensile strength decreased; The water absorption decreased at first and then increased; the test of rheology indicated that the latex was a newtonian fluid. With an increasing amount of styrene, the particle size, tensile strength and pencil hardness increased while the viscosity, water absorption and elongation at break decreased. The particle size and elongation at break decreased and the viscosity, water absorption, tensile strength and pencil hardness increased with the increasing amount of DMPA.