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Optimization and characterization of solution-cast fluoropolymer coatings

Meredith Lynn White, University of Massachusetts Amherst


New grades of fluoropolymers are available from DuPont that have been designed to relieve some of the processing problems associated with these materials. By nature, Teflon$\sp{\circler}$ is very viscous in the melt state, and only high energy processes allow material processing. These new grades of fluoropolymers are the first to be dissolvable, by perfluorinated solvents, and have opened up a whole new field of solution processing. It has been the aim of this work to investigate this new field of research. New solution processing techniques have been developed to create strong well-adhered coatings of fluoro-ethylene-propylene (FEP) copolymers to various substrate materials, ranging from 50nm to 100$\mu$m. By observing and exploiting upper and lower critical solution temperatures, solutions of concentrations up to 15 wt. % have been achieved, well above the 1 wt % solutions produced at DuPont. This enabled the formation of FEP coatings in one step, rather than attempting multiple layers to achieve greater thickness. Since these are experimental grades of FEP, physical properties have been investigated by thermal and x-ray analysis. In terms of coating properties, the coatings have shown remarkable adhesion properties measured by a unique self decohesion test approach. In order to define optimal uses for these materials as coatings, barrier properties have been measured. Permeability has been tested using carbon dioxide and air and Atlas cell corrosion tests have been run to compare the corrosion resistance among the copolymers being studied. Mechanical properties have also been characterized by holographic interferometry, which measures the in-plane residual stresses, and Instron testing, for tensile properties of the films. To improve coating quality, while taking advantage of the solution media, sol-gel reaction schemes have been modified by DuPont researchers to be carried out in these solvents in the presence of the dissolved FEP. The result is the formation of an SiO$\sb2$ network around the FEP molecules, producing a nano-composite material. This has been investigated with limited success on improving adhesion and other properties mentioned above.

Subject Area

Plastics|Materials science

Recommended Citation

White, Meredith Lynn, "Optimization and characterization of solution-cast fluoropolymer coatings" (1998). Doctoral Dissertations Available from Proquest. AAI9823789.