| Due to the improvement of People's awareness of environmental protection and international and domestic strict environmental regulations, coatings with low pollution and high performances have developed. Since wooden coatings have a very tight contact with people's lives, they have become hot research topics. Especially polyurethane acrylate (PUA) has become an important type of wooden coatings for its outstanding performances. There are lots of research emphasized on Toluene diisocyanate (TDI) polyurethane water-based coatings in domestic, but TDI-based polyurethane wooden coating is easy to yellowing, which does not meet the demands of high-quality wooden coatings about the anti-yellowing. In this dissertation, the aliphatic PUA composite emulsion used as high-quality wooden coatings was mainly developed.Polyurethane prepolymer was synthesized via step polyaddition, based on isophorone diisocyanate (IPDI),poly(propylene oxide) diol (N220) and PTMEG as raw materials, tri(hydroxymethyl) propane (TMP) as cross-linkers, 1,4-butanediol (BDO) as chain extender, dimethylol propionic acid (DMPA) as hydrophilic agent, and triethylamine (TEA) as neutralizer. Polyurethane dispersion (PUD) was obtained by dispersing PU prepolymer into water at a high speed of stirring with ethylenediamine (EDA) as another chain extender. Methyl methacrylate (MMA) was dispersed into PUD previously. Then polyurethane-acrylate (PUA) hybrid emulsions were synthesized by emulsion polymerization using 2, 2'-azobisisobutyronitril (AIBN) as initiator.Firstly polyurethane-acrylate (PUA) composite emulsions were synthesized based on poly(propylene oxide) diol (N220),PTMEG,policarbonatediol (PCDL) alone or based on their blends at different ratio. The performances of emulsions and their corresponding films with different diol as raw materials were compared particularly. At last the optimal recipe was confirmed that the emulsions and films have the best performances with 50% PTMEG instead of poly (propylene oxide) diol (N220).When the mass ratio of PTMEG and N220 was 1:1, effects of amount of organic solvent, reaction time and temperature of pre-polymerization, temperature of emulsion polymerization, mole ratio of -NCO/-OH, content of cross-linker (tri(hydroxymethyl) propane),content of hydrophilic chain extender (DMPA) and emulsification process on properties of waterborne polyurethane emulsions and their films were described and the optimal recipe and synthetic process were decided. The results showed that when the temperature of pre-polymerization was between 60℃~65℃and the time of pre-polymerization was 7.5h, the content of organic solvent was 15%, the preliminary mole ratio of -NCO/-OH was between 10.5~11.0 and the total mole ratio of NCO/OH was 1.35, the content of TMP was 2.0%, the temperature of Emulsification process was 20℃-30℃, the speed of impeller was between 4000-5000 r/min,using direct dispersion method and after-neutralization technology, the temperature of emulsion polymerization was 70℃-75℃, the amount of MMA was 20~30%, the emulsions and the corresponding films have best comprehensive properties.Modern instruments such as infrared spectroscopy (IR), gel permeation chromatography (GPC), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) etc. were used for tracing synthetic process and characterizing structures and properties of products. Infrared spectroscopy showed that -NCO and-OH groups were involved in the reaction to form the urethane groups; The analysis about tracing the synthetic process of PU by gel permeation chromatography showed that the increase of PU's molecular weight quickly was happened mainly in the chain-extending stage when EDA was added, and the molecular weight of the final product was more than 105; Scanning electron microscopy was used in characterizing film's break surface and results showed that section without cross-linking modification was smooth, and the modified section was very rough.
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