The Preparingand Application Of Two-Component Waterborne Polyurethane Coatings

Waterborne polyurethane coatings possess innoxious, odorless, no-harm to the environmentand safe characteristic, and now are gradually replacing traditional solvent-based coatings. Two -component waterborne polyurethane coatings which has almost same properties with solventbased coatings, has attracted much interest in the world. As a result of joining water, comparingto solvent based polyurethane, Two-component waterborne PU coatings lie in much difficulty.Two-component solventborne PU coatings must control water, because it is sensitive to NCOcomponent. chemical reaction will take place between them. But two-component waterborne PUcoatings regard water as solvent, there is much difficulty in its application and technology.Recently , the production and chemistry of two-component waterborne PU coatings have beenstudied successfully in overseas, for example that bayer company produces two-componentwaterborne PU coatings by acrylic emulsion and hydrophilically-modified polyisocyanate hasgained spreading.With improving of people recognization and development of coatingstechonology, two-component waterborne PU coatings will gain more applications.In this paper, hydroxyl component-acrylic dispersion was prepared for two-componentwaterborne polyurethane coatings. The influence of the components of these dispersions onpolymerization process such as hydroxyl value, acid value,Tg are investigated, by combined withhydrophilically-modified polyisocyanate. Scanning transmission electron microscopy(SEM)wasused to characterized the structure and morphology of film, in order to gain excellent waterbornepolyurethane coatings; The influence of mixing way, NCO/OH ratio,temperature,humidity wasinvestigated, and the reasons of pot life and air bubble were analysized. Finally applications oftwo-component waterborne polyurethane coatings in different materials were discussed.The indices of two-component waterborne polyurethane coatings by combining acrylicdispersion and hydrophilically-modified polyisocyanate were satisfied compared withsolvent-based coatings, and pot life was extended. These problems of two-componentwaterborne polyurethane coatings were settled by selecting proper technics and additives in theapplication such as lower gloss,hardness and bubble limitation of film.