Research On Preparation And Modification Of HMDI-based Waterborne Polyurethane

In recent years, the waterborne polyurethane(WPU) material has become one ofthe major research and development on the non-toxic, nonflammable, toughness,abrasion resistance, mechanical flexibility and do not pollute the air. However, thethermal stability, water resistance, solvent resistance and mechanical properties ofWPU are lower than those of the organic solventborne PU, which are considered closeto the organic solventborne PU in theory. In order to improve the properties of WPU,it is necessary to improve the formula and modify of WPU.In this work, the optimum formula of WPU obtained through the selection of rawmaterials,design of condition and adjusting formula. On this basis, for the sake ofenduing some electrical performance, carbon nanotubes and LiClO4were introducedto the WPU system.(1) Research on synthesis and properties of HMDI-based waterbornepolyurethaneIn this chapter, a series of WPU dispersions have been successfully synthesizedbased on dicyclohexylmethylmethane diisocyanate (HMDI), dimethylol propionicacid (DMPA) and low-molecular chain extenders (1,4-butylene diol (BDO))byprepolymer method. The WPU were characterized by Fourier transform infraredspectroscopy (FTIR). Other properties of WPU films, such as viscosity, waterresistance and tensile strength were also determined. The hard segment, DMPAcontent, R value on the properties of WPU were studied.The research results showed when the R value is1.05, the hard segment is35%and DMPA content is7%, the comprehensive performance of WPU is the best. Thewater resistance is better, the tensile strength is34MPa, the elongation at break is867.23%.(2) Research on synthesis and properties of carbon nanotubes/waterbornepolyurethane compositeIn order to study the effects of carbon nanotubes on properties of WPU, controlother polymerization condition, R value(1.05), hard segment(35%) and DMPAcontent(7%). The WPU emulsion were treating by PVP before using. The carbonnanotubes were doped to the system by physical blending method. The diameter andcarboxylated modification of carbon nanotubes on the properties of WPU compositewere studied.The research results showed that the larger diameter of carbon nanotubes, the properties of composite is better.Using PVP to process WPU emulsions improve thedispersion of carboxylated carbon nanotubes in WPU matrix. When the content ofTNM7-COOH is1%, the tensile strength is up to43.32MPa, the the elongation atbreak is966.23%. WPU composite material has some conductivity, the volumeresistance of composites is8.31×107Ω.(3) Research on synthesis and properties of LiClO4/waterborne polyurethanecompositeIn order to study the effects of LiClO4on properties of WPU, control otherpolymerization condition, R value(1.05), hard segment(35%).When the DMPA content is7%, the comprehensive performance is better. Thetensile strength is up to37.51MPa, the the elongation at break is1183%, the volumeresistance of composites is6.17×106Ω. It was revealed that the LiClO4contentincreased, which could make the degree of ionization improve, and water resistancereduce, the tensile strength and elongation at break improve.When the LiClO4contentis0.7times of the molar mass of DMPA, the comprehensive performance ofcomposite is better, the tensile strength is49MPa, the elongation at break is1145%,the volume resistance is3.74×106Ω。(4) Research on synthesis and properties of carbon nanotubes/LiClO4/waterborne polyurethane compositeIn order to study the effects of carbon nanotubes and LiClO4on properties ofWPU, control other polymerization condition, R value(1.05), hard segment(35%) andDMPA content(7%). The WPU emulsion were treating by PVP before using.Whencarbon nanotubes and LiClO4exist in the system at the same time, the propertieschange trend of composite were studied.The result indicated that the properties of composite changed a lot. The tensilestrength of composite reduced, the elongation at break improved and the electricalconductivity improved. When the content of carbon nanotubes is0.5%, the content ofLiClO4is0.6times of the molar mass of DMPA, the comprehensive performance ofcomposite is better.