Preparation And Properties Of Two-component Waterborne Polyurethane Coatings

In the field of environmentally friendly coatings, two-component waterborne polyurethane(2K-WPU) coatings represent a new technology, combining the good film properties of solventbased two-component coatings with the low volatile organic compounds (VOC) values ofwaterborne coatings. Two-component waterborne polyurethane coatings mainly comprise ofpolyols and polyisocyanates. Polyols can be divided into latex polyol and dispersion polyolaccording to the way of preparation. In this paper, acrylic latex polyol and acrylic dispersionpolyol were synthesized respectively. One kind waterborne polyisocyanate, which was waterbornehexamethylenediisocyanate (HDI) trimer, was obtained by hydrophilic modification. Andisophorone diisocyanate (IPDI) trimer (T1890E), which can formulate into 2K-WPU coatings withpolyols, was selected from the unmodified polyisocyanates. The effects of reaction technique and formula on the average diameter and stability of polyolparticles were addressed, and the rheology property of polyols was discussed during the synthesisprocess of polyols. The effects of average molecular weight of polyethylene glycolmonomethether and different hydrophilic component on the hydrophilic property of productionwere reviewed during the stage of hydrophilic modification of HDI trimer. Finally, three good 2K-WPU coating films were obtained by mixing above polyols withpolyisocyanates and then curing at different conditions. The effects of components and structuresof polyols and different proportion of polyol and polyisocyanate in mixing and film forming stageon the properties of coating films were addressed during the above process. After propertiescomparison of the above three kinds of coating films, it was shown that properties of the coatingfilm, which was acquired by mixing the acrylic dispersion polyol and modified HDI trimer and thencuring at the room temperature, are the best and approach the properties of the correspondingsolventborne two-component polyurethane coating films; but the content of VOC of it is only 36%of the latter, meeting the demand of environmental protection. Therefore, it has the wide prospectfor application.