GOALI - Fundamental Studies of Microstructure and Property Development in Novel Latex Coatings

Intellectual Merit:

This collaborative research explores the fundamentals of microstructure and property development in coatings created from engineered latex particles developed at Arkema, Inc. Arkema is a leading supplier of specialty chemicals that are used in the coatings industry and has been an innovator in the development of synthetic routes to new latex particles. The University of Minnesota has developed advanced techniques to monitor structure and property development in situ during drying and via time sectioning methods in which the coating is frozen at different stages of structure development and then examined in the frozen state by cryogenic scanning electron microscopy (cryoSEM). The overall aim of the research is to advance the understanding of the film formation and structure development in latex coatings using model systems that are industrially relevant and well suited to fundamental research. Two novel latex systems will be explored in this research: (1) block copolymer latex and (2) fluoropolymer acrylic latex. The block copolymer latex consists of nanostructured particles with a combination of hard and soft blocks in a microphase separated nanostructure. The role of this nanostructure on film formation is not understood. The objective of this part of the research is to connect the nanostructure of block copolymer latex particles with the film formation process and the final structure of the coating. Model block copolymer latex with a range of chemistries and morphologies will be synthesized at Arkema. CryoSEM will be used to track the development of structure during film formation so that connections to nanostructure can be made. The stages in structure development, from discrete particles through compaction and deformation to the final coalesced film, will be imaged in frozen specimens. AFM studies will complement the research. With the fluoropolymer-acrylic latex, the main objective is to characterize film formation and relate the structure development to stress and cracking. Understanding and controlling cracking is important to the application of latex materials. Arkema will provide model materials formulated with and without a coalescing aid. CryoSEM studies will be carried out in parallel with measurements of weight loss and stress development and observations of cracking in order to determine the origin of the stress that causes cracking and the role of the latex particle structure on the phenomenon. The second objective is to use a broader set of particles to explore connections between particle and process parameters on cracking, and ultimately to develop strategies to mitigate cracks.

Broader Impacts:

This research will impact the fields of coating processing, colloidal science, materials characterization, and particle mechanics. The results will broadly apply to other latex materials, feeding a growing effort in industry to replace solvent based polymer coatings with water-based latex coatings. The research will help to advance the scientific understanding so that companies can meet the challenges they face as they seek to improve the environment. The impact of the research will extend to multiple groups of students. First, the research will help the career development of the graduate student as well as the undergraduate researchers, who will join the effort in the summers. These students will learn not only from the research itself but also from the interactions with academic and industrial scientists. Second, the graduate students in the home department of the academic PIs will have the opportunity to participate in an industrial roundtable that involves the Arkema PIs. Third, a new experiment will be designed for an undergraduate course in Materials Processing. The students will design coating formulations to make a Cool Roof? using the fluoropolymer acrylic latex. Lastly, the PIs will develop a learning module that introduces K-12 students to engineering concepts, an important topic in light of recent changes to the science standards in the State of Minnesota. The module will also be built on basic concepts in film formation and will include engineering of a Cool Roof. A high school science teacher will join the team to help with the research and the development of the learning module. The Arkema Foundation will make the learning module available through its summer program for science teachers.