Monitoring diffusion and reaction rate during film formation of waterborne 2-pack polyurethane coatings

对环境的关注已经推动了涂料行业技术的重大变革。为了减少挥发性有机化合物（VOC）释放到大气中的量，人们正在开发新技术，用水性涂料取代溶剂型涂料。最大的挑战是在工业涂料领域，聚氨酯涂料在其中发挥着特别重要的作用，例如在汽车，航空航天，工业维护和塑料涂料应用中。高性能聚氨酯（PUR）涂料包括“2-pack”（2K）溶剂型配方，其中多异氰酸酯（PIC）和低分子量多元醇被分开包装，以避免组分的固有反应。这两种成分在使用前混合，然后必须在成分之间的反应变得太超前（“锅寿命”）之前将它们应用到基材上。水性（WB） 2K-PUR涂料是一种环保的溶剂型聚氨酯替代品，但这种技术要复杂得多。首先，多异氰酸酯必须分散在水中，在那里PIC和水之间的反应可能与与多元醇的反应相竞争。此外，多元醇以小颗粒而不是离散分子的形式存在。这对PIC和多元醇的反应方式有重要影响。虽然已经尝试研究WB 2K-PUR系统中的反应速率，但对于组分如何在分子水平上混合以及这如何影响涂层的最终性能，几乎一无所知。在这个项目中，我们将使用由多伦多大学的Winnik小组开发的特殊技术来研究PIC和多元醇混合物中聚合物的速率，并将其与化学反应发生的速率进行比较。我们将研究各种多元醇成分的工艺，并与巴斯夫的合作伙伴合作，将这些基本知识转化为高性能WB 2K-PUR涂料的设计。

Concern for the environment has been driving major changes in technology in the coatings industry. To reduce the amount of volatile organic compounds (VOC's) released to the atmosphere, new technology is being developed to replace solvent-based coatings with water-based coatings. The biggest challenges have been in industrial coatings, where polyurethane coatings play a particularly important role, for example in automotive, aerospace, industrial maintenance, and plastic coatings applications. The highest performing polyurethane (PUR) coatings involve "2-pack" (2K) solvent-based formulations in which a polyisocyanate (PIC) and a low molecular weight polyol are packaged separately to avoid the intrinsic reaction of the components. The two components are mixed just prior to use and then they have to be applied to a substrate before the reaction between the components becomes too advanced (the "pot life"). Waterborne (WB) 2K-PUR coatings have been developed as an environmentally friendly alternative to solvent-based polyurethanes, but this technology is much more complex. First, the polyisocyanates have to be dispersed in water, where reaction between the PIC and water can occur in competition with the reaction with the polyol. In addition, the polyol is present as small particles rather than discreet molecules. This has a major effect on the way the PIC and polyol react. While attempts have been made to study reaction rates in WB 2K-PUR systems, almost nothing is known about how the components mix at the molecular level, and how this affects the final performance properties of the coating. In this project, we will use special techniques developed by the Winnik group at the University of Toronto to study the rates at which the polymers in the PIC and in the polyol mix and how this compares to the rates at which the chemical reactions occurs. We will study these processes for a wide range of polyol compositions, and we will work with our partners at BASF to translate this fundamental knowledge into the design of high performing WB 2K-PUR coatings.