水性聚氨酯乳液和成膜性能简介

水性聚氨酯乳液性能
Properties of waterborne polyurethane emulsion
介质水中聚氨酯微粒的粒径大小对乳液的稳定性、成膜性、对基材的湿润性能、膜性能及粘接强度等性能有较大影响。在配方基本不变、亲水性基团含量基本相同的情况下，乳液粒径的减小，有利于提高乳液的稳定性和胶膜性能。乳液稳定性还与亲水基团含量和乳液颗粒表面的离子基团有关。表面张力是关系到水性聚氨酯对基材湿润性的重要因素。水性聚氨酯的表面张力一般在 0.040-0.055N/m范围。为了有效地使水性聚氨酯均匀涂覆在塑料等低表面能物质的表面上，可添加润湿剂以降低乳液的表面张力。水性聚氨酯的黏度对固含量的依赖较大，黏度主要与树脂的离子电荷数量、颗粒结构等因素有关。可以根据施工方式和用途对水性聚氨酯的黏度进行调整，如使用增稠剂等。
The particle size of polyurethane particles in aqueous medium has a great influence on the stability, film-forming properties, wetting properties, film properties and bonding strength of the substrate. When the formula is basically unchanged and the hydrophilic group content is basically the same, the decrease of emulsion particle size is beneficial to improve the emulsion stability and adhesive film performance. The stability of emulsion is also related to the content of hydrophilic groups and the ionic groups on the surface of emulsion particles. Surface tension is an important factor that affects the wettability of waterborne polyurethane to substrate. The surface tension of waterborne polyurethane is generally in the range of 0.040-0.055N/m. In order to effectively apply waterborne polyurethane on the surface of plastic and other low surface energy substances, wetting agent can be added to reduce the surface tension of emulsion. The viscosity of waterborne polyurethane depends greatly on the solid content, and the viscosity is mainly related to the number of ionic charges and the particle structure of the resin. The viscosity of waterborne polyurethane can be adjusted according to the construction methods and uses, such as thickening agent.

水性聚氨酯成膜性能
Properties of waterborne polyurethane film
水性聚氨酯干燥后，具有弹性体的外观和性能。由于聚氨酯原料的多样化，由水性聚氨酯也能制得从软质到硬质的干膜。通过热处理，一般能提高胶膜的强度和耐水性能，在乳液中添加交联剂一般也能提高胶膜强度，但有时会降低其延伸率。水性聚氨酯树脂一般含有亲水性基团。在干燥固化过程中，若离子型聚氨酯的成盐剂能够逸出，则胶膜会获得一定的疏水性；如果成盐剂不能够逸出，亲水性基团残留，并且成膜时未发生基团之间的交联反应，则胶膜耐水较差。
After drying, waterborne polyurethane has the appearance and properties of elastomer. Because of the variety of polyurethane raw material, the dry film from soft to hard can be prepared by waterborne polyurethane. Generally, the strength and water resistance of the adhesive film can be improved by heat treatment. The addition of crosslinking agent in the emulsion can also improve the strength of the adhesive film, but sometimes it will decrease its elongation. Waterborne polyurethane resins generally contain hydrophilic groups. In the dry curing process, if the ionic polyurethane salt forming agent can escape, then the film will obtain certain hydrophobicity; if the salt forming agent can not escape, hydrophilic groups and residual film without crosslinking reaction between the groups, while the film water resistance is poor.