Synthesis And Properties Of High-performance Aqueous Polyurethane Dispersions

Polyurethane (PU) has been widely used due to their good mechanical and excellentchemical resistance properties. With the improvement of people’s awareness ofenvironmental protection, the environmental regulations in various countries very strictlylimited the contents of volatile organic compounds (VOC) in coating industry, whichpromoted the development of water-based coatings, specifically waterborne polyurethane(WPU) coatings. Compared with solvent-based PU coatings, WPU has been attracted muchattentions in coatings, adhesives and leather finishing agents because it display manyadvantages in the production, transportation, use of safety and also do not pollute theenvironment. However, The presented waterborne polyurethane carried amount of organic-tincatalyst and N-methyl pyrrolidone (NMP) which harmful to the environment, it also exhibitslow solids content (about35%), slowly dried speed, poor chemical resistance and filmappearance, all of these limited their applications and development.The aqueous polyurethane dispersions (PUD) free NMP and organic-tin catalyst wereprepared with the aminased DMPA as a hydrophilic chain extender, and the effects aminationprocess on the preparation technology and properties of PUD were investigated. Thestructures and the properties of PUD films were also studied. It was found that theamination process display simple, feasible and environment-friendly due to it could preparePUD with excellent properties and avoid using both organotin catalysts and NMP solvents.The high solids content PUD was synthesized via prepolymer dispersion process withaminated DMPA and ethylenediamine sulfonate (N60) as the composite hydrophilic chainextenders. The effects of the soft segment composition, the proportion of the soft and hardsegments, the amount, ratio and additive process of the hydrophilic components, the amount,species and chain extender process of the amine chain extender and overall NCO/OH molarratios on the PUD and its film properties were discussed. The results showed that optimalproportion of soft and hard segments was40~50%, as well as the4.5~6wt%of thehydrophilic components with0.6/0.4~0.8/0.2of the ratios, and the optimal amine chainextender extent was60~80%, which was added with water after emulsification, N60was added directly before emulsification and the overall molar ratios of NCO/OH was1.3~1.6.PUDs with a solid content of at least45%was obtained by crosslinking modified with TMPand organosilane, and found that its film possesses excellent chemical resistance includingwater-, alcohol-and alkali-resistance, etc. and high hardness as well as does not contain NMPand organic tin.