Methanol degradation mechanisms and permeability phenomena in novolac epoxy and polyurethane coatings
نویسندگان
چکیده
On a global scale, methanol is one of the most important feedstocks and used widely as solvent co-solvent. However, due to polar nature associated ability conduct current, small molecule can take part in galvanic corrosion metal storage tanks degrade barrier properties protective coatings. In present work, we investigated degradation two novolac epoxy coatings polyurethane (PU) coating exposed with aim quantifying various paths. Absorption desorption rates were measured thermomechanical followed by dynamic mechanical analysis. For evaluation (i.e., breakthrough time steady state permeation methanol), cells applied. During absorption, simultaneous leaching certain ingredients bonding binder matrix via hydrogen bonds was evidenced. terms classification, took place types mechanisms. Type I, forms single bond network, thereby acting plasticizer, which decreases modulus glass transition temperature. II methanol, on other hand, network form per molecule, resulting so-called physical crosslinking. The I mechanism boosted segmental mobility contributed plasticizer benzyl alcohol from residual solvents naphtha xylene) PU coating. Following desorption, attributed an increased effective crosslinking density bound exhibited significant increases temperatures. addition, for three coatings, gradual decline permeability rate observed over time. These enhanced (and unexpected) result combination effects ascribed process.
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ژورنال
عنوان ژورنال: Journal of Coatings Technology and Research
سال: 2021
ISSN: ['1547-0091', '2168-8028']
DOI: https://doi.org/10.1007/s11998-020-00446-w