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首页> 外文期刊>Journal of coatings technology and research >Model-based analysis of photoinitiated coating degradation under artificial exposure conditions
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Model-based analysis of photoinitiated coating degradation under artificial exposure conditions

机译：基于模型的人工暴露条件下光引发涂层降解的分析

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摘要

Coating degradation mechanisms of ther-moset coatings exposed to ultraviolet radiation and humidity at constant temperature are investigated. The essential processes, photoinitiated oxidation reactions, intrafilm oxygen permeability, water absorption and diffusion, reduction of crosslink density, and development of a thin surface oxidation zone are quantified and a mathematical model for degrading coatings developed. Front-tracking techniques are used to determine the rate of movement of the oxidation and ablation fronts, the positions of which define the extension of the surface oxidation zone. Three previous and independent experimental investigations with two-component, densely crosslinked, epoxy-amine model coatings were selected for verification of the mathematical model. Simulations can match and explain transient mass loss and coating thickness reduction data and are in agreement with infrared measurements of carbonyl groups formed in the surface zone. The thickness of the stable surface oxidation zone, which is established after an initial ablation lag time, is estimated by the model to 0.5-2 μm in good agreement with previous measurements. Simulated concentration profiles of active groups, oxygen, and radicals in the stable surface oxidation zone are presented and analyzed. The mathematical model can be used for obtaining a quantitative insight into the degradation of thermoset coatings and has potential, after further development, to complete commercial coatings and dynamic exposure conditions, to become a supplementing tool for predicting in-service coating behavior based on accelerated laboratory measurements.
机译：研究了在恒定温度下暴露于紫外线和湿气的热固性涂料的涂层降解机理。量化了基本过程，光引发的氧化反应，膜内透氧性，吸水和扩散，交联密度的降低以及薄表面氧化区的形成，并建立了用于降解涂层的数学模型。前沿跟踪技术用于确定氧化和烧蚀前沿的运动速率，其位置决定了表面氧化区的延伸。选择了三项先前和独立的实验研究，用两组分致密交联的环氧胺模型涂料进行数学模型验证。模拟可以匹配并解释瞬态质量损失和涂层厚度减小的数据，并且与在表面区域中形成的羰基的红外测量结果一致。该模型将初始烧蚀滞后时间后建立的稳定表​​面氧化区的厚度估计为0.5-2μm，与先前的测量结果非常吻合。给出并分析了稳定表面氧化区中活性基团，氧和自由基的模拟浓度分布。该数学模型可用于获得对热固性涂料降解的定量了解，并有可能在进一步开发后完成商业化涂料和动态暴露条件，成为基于加速实验室预测服务中涂料行为的补充工具。测量。

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