| Summary: | 碩士 === 國立高雄科技大學 === 化學工程與材料工程系 === 107 === In this work, a series of solvent-free, high solid content and low viscosity waterborne polyurethanes (WPU) were successfully prepared by prepolymer process. The NCO-terminated prepolymer was synthesized by using polypropylene glycol (PPG), polytetramethylene ether glycol (PTMG), hydrophilic di-ol monomer dimethylolpropionic acid (DMPA) and an excess of isophorone diisocyanate (IPDI). After neutralized by TEA, then dispersed in deionized water containing AAS, finally extended chain with ethylenediamine (EDA). WPU dispersion with solid content of 50 wt% was obtained. To explore the effect of the NCO/OH molar ratio, degree of side chain, hydrophilic group content on the viscosity of WPU. The chemical structures of the waterborne polyurethane were characterized by infrared spectroscopy (FT-IR), the number average molecular weight of the WPU were measured by gel permeation chromatography (GPC), which confirmed that the polymerization reaction had been successfully carried out. In addition, the micelle size of the WPU were identified by particle size analyzer. The tensile strength, elongation at break were measured by universal tensile testing machine. The results of experiment indicated that the micelle size of WPU emulsion was decreased as the PPG/PTMG molar ratio increased, and the viscosity increased. Because the PTMG was a long-chain hydrophobic polyol, hydrophobic polyol will produce larger micelle size and longer molecular chain may coat hydrophilic group, resulting poor hydrophilicity, and then form larger micelle size. Finally, 50 wt % solid content solvent free WPU was obtained by incorporating of PPG to blend with PTMG with the molar ratio of 1:3, viscosity of 255.5 cP. The final product displayed water absorption was 13.48 %, water dissolution rate was 12.48 %.
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