Synthesis And Characterization Of Waterborne Polyurethane Dispersion Based On Polycarbonate Diols

With the environmental regulations being increasingly stricted, countries have imposedserious restrictions on volatile organic compounds (VOCs) and toxicants, therefore, it is veryurgent to develop the green polyurethane materials with outstanding performances. Thewaterborne polyurethane (WPU) has meet with low VOC emissions standard, in recentdecades it has seen the rapid development of WPU. But WPU has poor performance in waterresistance, high temperature resistance and thermal stability, which has limited thedevelopment and application of WPU. It has great significance and prospects to develop novelWPU with good performance in water resistance and thermal stability.In this thesis, two types of end-capped WPU were prepared by means of the prepolymerdispersion method using hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI)and polycarbonate diols (PCDL), polytetrametlylene glycol (PTMG) as basic material,dimethylol propanic acid (DMPA) and1,4-butanediol were used as chain extender,aminopropyl trimethoxysilane (KH-551) and triethylamine (TEA) were used as end-cappingreagent and neutralizing agent, respectively. The structure and thermodynamic property ofWPU were characterized by FT-IR, thermogravimetric analysis (TGA), differential scanningcalorimetry (DSC). Besides, the appearance, stability, viscosity of the WPU emulsionsperformance and solvent resistance, mechanical performance and shear adhesive strength ofWPU film were also discussed. The main work and research results of the chapter includefour aspects:(1)-NCO end-capped WPU was prepared with PCDL and PTMG as softsegment, separately. The results indicated that the combination property of PCDL-WPU wasbetter than PTMG-WPU, which possessed better solvent resistance, higher thermal stabilityand mechanical performance.(2) A series of-NCO end-capped WPU were synthesized byusing HDI/IPDI and PCDL. The properties of WPU emulsions and films were analyzed bydifferent rates of HDI/IPDI. The results showed that with the increase of HDI/IPDI rates, theappearance of WPU emulsion became worse, the viscosity increased, the elongation at break,solvent resistance, thermal stability and compatibility of WPU film were improved; the tensile strength and tensile shear strength of WPU films were both increased preliminarily and thenreduced.(3) The WPU end-capped with silane coupling agent (KH-551) was prepared withIPDI and PCDL as main raw materials, and silane couping agent as end-capped agent. Theeffects of adding KH-551content on the properties of WPU were investigated. The results ofthe study showed that with the increase of KH-551conten, the appearance and stability ofWPU emulsions had little changes, emulsion viscosity, tensile strength and tensile shearstrength of WPU film were all increased preliminary and then reduced, the elongation at breakof WPU film was reduced, the initial decomposition temperature increased, and the solventresistance of film was reduced firstly and then increased. By considering, the better KH-551content should be at2%.(4) Polysiloxane-polycarbonate diol-waterborne polyurethaneterpolymer was synthesized by using IPDI and PCDL as main raw materials, and the differenttypes of polysiloxane as modifier. The effects that the various kinds and different additivequantity of polysiloxane on the properties of WPU emulsions and films were discussed. Thestructure and morphology of the WPU films were characterized by using FT-IR and scanninglectron microscopy (SEM), and the thermal properties of WPU were characterized by usingthermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Themechanical properties, water and ethanol resistance of the film were also tested in this chapter.It was shown that the compatibility of WPU chain became poor with PDMS joined, andexisted a micro phase separation in them, thus leading to a decreased tensile strength.However, the thermal stability and water resistance of the films were both improved. Besides,the elongation at break and tensile shear strength were both increased preliminary and thendecreased; and the ethanol resistance of PDMS-NH2modified WPU films was significantlyimproved, while the ethanol resistance of the PDMS-OH modified WPU films was worse.Compared and analysised the modification effect of PDMS-OH and PDMS-NH2, we cangenerally concluded that PDMS-NH2was more suitable for the modification on WPU.