2001 TSE: Formulating Waterborne Coatings for the Environment: Interactions in Water-Cosolvent Media between Associating Polymers, Surfactants, and Colloidal Particles
Paschalis Alexandridis Principal Investigator
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Abstract<br/>CTS-0124848<br/>Alexandridis, P<br/>SUNY Buffalo<br/><br/>Formulating Waterborne Coatings for the Environment: Interactions in Water-Cosolvent Media between Associating Polymers, Surfactants, and Colloidal Particles<br/><br/>Background: The coatings and paints industry commands a 50 billion-dollar market worldwide. Over 1 billion gallons of coatings and paints are sold in the U. S. every year. Because of increased environmental awareness and under regulatory pressure for the reduction of volatile organic compound (VOC) emissions (e.g., Pollution Prevention Act of 1990), over half of the coatings and paints are now waterborne, and the trend for increasing the fraction of waterborne formulations continues. But even waterborne coatings and paints are not VOC-free, as they contain cosolvents, which may comprise up to 30% of the total liquid present. Furthermore, a number of these cosolvents are classified as hazardous air pollutants (HAP).<br/><br/>Motivation: There is a need for both an overall reduction of VOC cosolvents and a replacement of HAP cosolvent by non-HAP ones. This need challenges the waterborne coating and paint formulations, but the drive for reformulation is confounded by the dearth of reports in the open literature regarding the effects of cosolvents on the aqueous solution behavior of associating polymers and surfactants. These amphiphiles are essential in stabilizing the resin and pigment colloidal constituents of coatings and paints and in conferring unique rheological properties (e.g., very high viscosity at rest and very low viscosity during the spraying or brushing application). <br/><br/>Research objectives: It is the goal of the principal investigator to develop fundamental knowledge to support and guide the optimal formulation of waterborne coatings and paints. The specific objectives are the following: Objective 1 is to establish benchmarks by examining the phase behavior, structure, and dynamics of aqueous solutions consisting of associating polymers and surfactants representative of those used in coatings and paints. Objective 2 is to explore and quantify the effects of various cosolvents (e.g., different types of glycol ethers and other polar solvents) on the phase behavior, structure and dynamics of aqueous solutions consisting of associating polymers and surfactants. No such information is currently available in the open literature. Cosolvents can have a profound effect on the solution behavior and interactions of amphiphiles, and also modify the overall and local viscosity of the system. Objective 3 is to study the colloidal stability, structure, and rheology of colloidal suspensions of resins or pigments in aqueous-cosolvent media that contain associating polymers and surfactants. Such suspensions are very similar to the ones used in coatings and paints. Of explicit consideration here is the fact that the cosolvents can interact specifically (e.g., partition or swell) with the resins. Another very important issue to consider is the change in the overall and the local composition (and corresponding interactions) of the particle-polymer-surfactant-cosolvent mixture as the water and cosolvents evaporate following the application of the coating/paint.<br/><br/>Potential Impact: The proposed research directly enables (i) the reduction of VOC cosolvents that are used in waterborne coatings and paints and the switch to cosolvents that are not HAPs, (ii) the optimal formulation of waterborne coatings and paints which would result in overall reduction of coating material (and associated energy costs) needed; (iii) at the same time the proposed work assists (by providing fundamental information) the ongoing efforts of replacing organic solvent-borne coatings and paints with environmentally friendlier waterborne formulations.