| Due to its environmental friendliness, being free of toxicity and pollution and not flammability etc., waterborne polyurethane has been wide applied in many fields and daily lives. During the synthesis of waterborne polyurethane, water is used as dispersant instead of organic solvent, therefore the emission of volatile organic compounds can be largely reduced. However, it is also because of the presence of water which would lead two inherent problems to waterborne polyurethane.Firstly, the drying time for waterborne polyurethane is longer than that for oil-soluble polyurethane when they have the same solid content. This is bad for fast-paced modern production line. The increase of the solid content is one of the most effective ways to solve this problem. It is reasonable that high solid content dispersions would attract more interest because of the reduction of water content which allows us to reduce film-formation and drying time. It does not only make applications more efficient, but also reduces energy load needed in some cases. In addition, it will make product transport more efficient and less costly. So this is one of the possible developing trends of aqueous polyurethane and high solid content waterborne polyurethane will gradually become more attractive. However, in the most of previous researches, the solid content of aqueous polyurethane only ranges from 20% to 35%. At the same time, there are not a significant number of papers available in the open literature that describe the synthesis of high solid content aqueous polyurethane and most of the work published on this subject seem to be in the patent literature.Secondly,in order to prepare waterbrone polyurethane emulsion,the introduction of hydrophilic groups is necessary. However, owing to the introduction of hydrophilic groups, the membrane of WPU have high surface energy, poor resistance to water and oils.In this study, two kinds of anionic waterborne polyurethane emulsion PTMG-PU ?and PCLD-PU were prepared respectively using isophorone diisocyanate (IPDI), polytetramethylene glycol (PTMG), polycaprolactone diol (PCLD), dimethylol propionic acid (DMPA) and butanediol (BDO) by self-emulsification method. FTIR spectra confirmed the structural differences between PTMG-PU and PCLD-PU. The effect of some factors during preparation process of waterborne polyurethane on emulsion viscosity and particle size was investigated systematically. It was found that the stable polyurethane emulsion of solid content over 40% with appropriate viscosity, particle size could be easily prepared as controlling neutralization value of 90-100%, [NCO]/[OH] value of 1.13-1.20, DMPA content of 2.5-9.0%, rotating speed of 1500-2000 r/min, adding water speed of 100-200 ml/min (the total volume of system was 200ml).In order to increase water resistance of waterborne polyurethane, a novel fluorinated diol 3-(bis-(N, N-dihydroxyethyl)) dodecafluoroheptyl acrylate (DEFA) was synthesized by using diethanolamine and dodecafluoroheptyl acrylate. Based on IPDI, PTMG, DMPA and BDO, polyurethane IPDI-DEFA-PU emulsion with long branched chain of fluorine was synthesized using DEFA as chain extender by self-emulsification method. The chain structure of DEFA and IPDI-DEFA-PU was confirmed by the analysis of 1H NMR and Fourier transform infrared spectroscopy. With fluorine content increased from 0 to 15.1 %, the particle size of emulsion increased from 102 nm to 260 nm, the surface tensile force of latex film decreased from 42.9 mN/m to 16.5 mN/m while the water contact angle increased from 71°to 104°, the swelling ratio of latex film in water and cyclohexane decreased from 15.8 % to 1.1 % and from 28.8 % to 3.4 % respectively. Meanwhile, water resistance, organic solvent resistance and thermal stability were all improved. As tensile strengths increased from 9 MPa to 15 MPa, extensibility decreased from 520 % to 280 %. |
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