Date of Award
2000
Degree Type
Dissertation
First Advisor
Sze C. Yang
Abstract
In the aircraft industry, the chromate conversion coatings are the current choice for corrosion protection of aluminum alloys. However, due to their highly poisonous nature, especially the potential carcinogenic effect, the EPA has passed regulations in 1998 calling for the eventual replacement of these coatings. Various replacement coatings systems are being actively explored. So far, nothing has been found with the matching performance of corrosion protection of Alodine 600 and 1200 industry chromate conversion coatings. Conducting polymers, especially the water-based PAN/PAA copolymer, as evidenced by our previous research, has the potential to perform as well as the chromate conversion coatings with further development. The PAN/PAA copolymer based coatings have the ease in application and less environmental hazard. The corrosion protection capability of PAN/PAA copolymer comes mainly from its electroactive nature. The performance at higher pH environment deteriorates rapidly due to the loss of conductivity when the polymer changes from its green conductive form to its blue non-conductive form. This work is positioned to resolve the pH limitation of these coatings. The idea is to utilize the combined properties of novel conducting polymer--inorganic compounds hybrid composite materials. In this approach, the pH limitation of the PAN/PAA copolymer can be improved greatly with the incorporation of chemically acidic transition metal compounds, such as molybdenum trioxide, tungsten trioxide and zirconium hydrogen phosphate. The interaction of the PAN/PAA copolymer with the transition metal compounds in aqueous and ethyl acetate media has been studied systematically. The composite formation process is a complex, self-assembling, self-organizing process that takes place at equilibrium conditions. This process involves the possible defoliation of the layered transition metal compounds and insertion of polymer molecules. The adsorption rate and conditions have been determined through kinetic and adsorption isotherm measurements. The novel conducting polymer--inorganic compounds composite materials were then synthesized and characterized. The defoliation process during the composite formation has been monitored by solution viscosity. The improved base resistance and capacity of the novel composite materials have been confirmed by acid base titration. Compared with a pH of 4 to 5 limitation in the case of pure PAN/PAA copolymer based coating, the conducting green form of the novel composite material has been extended up to above pH = 7. The composite formation in ethyl acetate media has some advantages over aqueous solution in terms of adsorption rate and ease of handling in separating, drying and grinding of the products. In this study, an esterified form of the PAN/PAA copolymer, methoxy polyacrylic acid and polyaniline is used instead of PAN/PAA copolymer. The potential use of this esterified PAN/PAA copolymer as a primerless Epoxy coating was investigated. Initial tests showed promising results. Further work is needed to improve the wetting and adhesion on the metal surfaces.
Recommended Citation
Chang, Kaiguo, "Synthesis and characterization of conducting polymer-inorganic composite materials" (2000). Open Access Dissertations. Paper 1896.
https://digitalcommons.uri.edu/oa_diss/1896
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