Synthesis And Structural Characterization Of Acrylic-modified Waterborne Polyurethane

The research in waterborne polyurethane(WPU) develops very quickly. It is friendly to environment because the low volatile organic compound is caused by little organic solvent used in the preparation and the usage of WPU. Compared with organic solvent polyurethane, WPU has some disadvantages such as bad film polish ,longer time of film preparation , hard endurance to corrosion , bad lowness of solid content, hard performance of wetting ability to backing and expensive price and so on. In order to overcome the defects in applications, WPU should be modified by introducing some resins.NCO-envoloped polyurethane prepared with isophorone diisocyanates(IPDI), polyester polyhydric alcohol and dimethylolpropionic acid(DMPA) was enveloped with hydroxyl ethyl methyl acrylate(HEMA ).Then the system was neutralized with triethylamine (TEA) .The pre-WPU was obtained by the system emulsified to water. Waterborne arylic-modified polyurethane was prepared by making pre-WPU polymerized with methyl methacrylate. And the synthesis and the factors affecting some of performance of WAPU were researched and the structure of WAPU was characterized in this paper.The best technique conditions were obtained which is 60 minutes, 80C pre-polymerizing temperature, 30C neutralizing temperature, 0.5 hour emulsifying time, 70C copolymerizing temperature and 2 hour copolymerizing time. The stability of products increased with the adding of Ri within the range of 1.2 to 1.4 and decreased with the adding of Ri within the range of 1.4 to 2.0, which was found by adjusting the factors influencing the stability of the dispersions. That the viscosity of dispersions increased with the adding of the content of dimethylolpropionic (DMPA) was discovered , which was moderate when the content of DMPA was 6%. PU chains moved quickly and the hydrogen bonds ruptured along with the increasing of dispersions temperature, which led to the interaction of the chains weakened and the viscosity decreased.The obvious hydrogen bond actions presented by WAPU were showed by FT-IR. The system showed compatible ability because a few carboxyl anions of themolecular chains of acrylate the hydrogen bond exited not only in the chains of PU but also the chains between PU and acrylates. The apparent activated energy of the film of the product prepared by water and IPDI was calculated by the method of Ozawa and Kissinger, which was 60.676 kJ/mol and 59.440kJ/mol respectively. By the TG analysis curve of the products film of the isocyanates respectively reacted with water, DMPA and the films of PU and WAPU, we found the decomposing temperatures increased in turn. The resistance to heat increased in turn was showed. The thermal weightlessness of first stage caused by the degradation of the hard segment ,which mainly was the fracture of the bond N-C , was found by the TG curves and superficial FT-IR of WAPU. By the DSC of WPU we found the Tg of the soft segment and the hard segment were respectively 7.58C, 124.69C and that of the DSC of WAPU is -0.71 C, 129.20C.From SEM photograph film surface of pre-WPU showed asymmetry and the chains integrated loosely, while the same of WAPU showed symmetry. That the film of WPU was found scale-like showed the molecular arranged partially order. SEM photograph showed the random status that the partial order of WAPU molecular was destroyed by copolymerzing of acylate .