Change of polymeric gel structure of several foamed plastic insulations deteriorated by moisture
Change of polymeric gel structure of several foamed plastic insulations deteriorated by moisture
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DOI：
10.1016/j.matpr.2023.07.021
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发表时间：
2023-07
期刊：
影响因子：
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通讯作者：
Yoobin Leem;R. Kitagaki
中科院分区：
文献类型：
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作者：
Yoobin Leem;R. Kitagaki
在可持续发展目标下，发泡塑料绝缘材料要求具有长期性能。然而，近年来，据报道，在高湿度环境中安装泡沫塑料绝缘材料，例如在屋顶的防水片下，吸收水分并随后增加导热性。本研究旨在评估高湿条件下泡沫塑料绝缘材料的吸湿性和物理性能的变化，并在多次实验的基础上讨论湿致劣化。我们观察了酚醛泡沫塑料、聚氨酯泡沫塑料和挤压聚苯乙烯泡沫塑料三种类型的泡沫塑料绝缘材料在受潮变质的情况下发生的变化。在第一步，我们验证水分以什么形式存在，以及变质后水分是否在材料内部凝结或与材料混合。准确地说，将两个试验结果对比高温湿变质前后的重量变化。一种是用x射线CT改变变质保温层的聚合物凝胶结构，另一种是用气体吸附法测定每个保温层表面吸附的水蒸气量。这些研究结果表明，变质的酚醛泡沫和水分可以混溶，从而改变聚合物凝胶结构。第二步比较水分恶化如何影响隔热材料的热特性。我们在之前的研究中评估了当绝缘材料暴露于季节性湿度周期时，适用于东北亚国家的典型季节性波动，对样品的影响比持续条件更严重。因此，我们研究了湿度波动中热特性与水分劣化效应之间的关系。结果，酚醛泡沫的聚合物凝胶结构发生了变化，其热性能受到湿度波动的影响。研究结果提供了部分湿气变质机理，湿气与泡沫塑料绝缘材料的混相行为改变了聚合物凝胶结构，从而改变了热性能。
Foamed plastic insulations require long-term performance under sustainable development goals. However, in recent years, it has been reported that foamed plastic insulations installed in high-humidity environments, such as under waterproof sheets on a rooftop, absorb moisture and subsequently increase thermal conductivity.The study aims to estimate both moisture absorption and changes in physical properties of foamed plastic insulations after exposure to high humidity and discuss the moisture-induced deterioration based on the results of several experiments.We observe what changes occur in three types of foamed plastic insulation, phenolic foam, polyurethane foam, and extruded polystyrene foam, in a deterioration condition with moisture. In the first step, we verify that the moisture exists in what form and whether moisture condenses inside or blends with the material after deterioration occurs. Precisely, comparing weight changes before and after high-temperature humidity deterioration with two test results. One is changing a polymeric gel structure of the deteriorated insulation with X-ray CT, and another is the amount of adsorbed water vapor on the surface of each insulation with the gas adsorption method. Results from these studies refer that the deteriorated phenolic foam and moisture are assumingly miscible to transform polymeric gel structure.The second step compares how moisture deterioration affects insulation’s thermal characteristics. We evaluated in our previous study when insulations are exposed to the seasonal humidity cycle to apply typical seasonal fluctuation in Northeast Asian countries, affecting more critical damage than a persistent condition to samples. Therefore, we examine the relationship between thermal characteristics and moisture deterioration effect in humidity fluctuations. Resultantly, the phenolic foam’s polymeric gel structure is changed, and its thermal property is affected by humidity swings.The results provide a part of the moisture deterioration mechanism, miscible behavior between moisture and foamed plastic insulations to change polymeric gel structure, which shifts thermal properties.