Analytical Evaluation and Mechanistic Elucidation for Solvent Degradation of Polymeric Materials




Daniels, Grant C

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Polymeric coating materials have been used for decades to protect various substrates from degradation, such as corrosion, which can cause failure of important aspects in vehicles and buildings. The proper removal of polymeric coating materials is as important as their protection of underlying substrates since improper removal will damage the substrate. Methylene chloride and phenol based removers have been utilized for this purpose for over 50 years. During which time little understanding of the mechanism for the degradation of polymeric materials from these solvents has been developed. This work employed two military polyurethane coatings in three different formulations: full, partial and clear. Simplified formulations and control mixtures of solvents commonly used in methylene chloride and phenol removers were developed in order to deconvolute analysis of the complex polymeric material and the solvent systems. The polymeric coatings were exposed to the different solvents and solvent solutions. Analyses were conducted utilizing multiple techniques to determine the mechanism for the degradation of polymeric coatings. These analyses revealed that methylene chloride solvated and swelled the coating while phenol degraded the polymer by nucleophilic attack. It was also determined that the addition of water to the solution significantly increased degradation. The enhanced degradation arose from the water molecule abstracting the proton from phenol, which increased its nucleophilicity.



Polymeric coatings, Phenol, Polyurethanes, Methylene chloride, Spectroscopy