PHYSICAL AND CHEMICAL EFFECTS IN AN EPOXY-RESIN EXPOSED TO WATER-VAPOR
PHYSICAL AND CHEMICAL EFFECTS IN AN EPOXY-RESIN EXPOSED TO WATER-VAPOR
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DOI：
10.1080/00218469508014353
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发表时间：
1995-01-01
影响因子：
2.2
通讯作者：
SHANAHAN, MER
中科院分区：
文献类型：
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作者：
DENEVE, B;SHANAHAN, MER
一种基于 DGEBA 的商用环氧粘合剂，用双氰胺 (DDA) 固化并含有填料，已在不同高温下的水蒸气（约 100% RH）中老化。在老化不同时间直至饱和之后以及随后的干燥之后进行粘弹性表征。玻璃态的杨氏模量在吸水后降低，但在干燥后几乎恢复到其原始值，这表明由于塑化而导致物理减弱，而在橡胶态下，观察到的减小在干燥时仅略有恢复。基于橡胶弹性理论的分析得出这样的结论：化学降解是通过水解和断链发生的。对暴露于蒸气固定时间然后干燥至（虚拟）平衡的聚合物进行的重量分析显示，随着暴露时间的增加，重量增加，然后减少，最后重量损失。提出了一种理论来解释这种现象，即水的初始化学结合，然后是切断的链段的浸出。使用粘弹性和重量数据计算的平均交联间分子量非常一致。结论是，环氧粘合剂长期暴露于水会导致材料的可逆（物理）和不可逆（化学）降解。
A commercial epoxy adhesive based on DGEBA cured with dicyandiamide (DDA) and containing fillers has been aged in water vapour (ca. 100% RH) at various elevated temperatures. Viscoelastic characterisation was effected after ageing for various times up to saturation and after subsequent drying. Young's modulus in the glassy state is reduced after water sorption but returns virtually to its original value after drying, suggesting physical weakening due to plasticisation whereas, in the rubbery state, the observed diminution is only slightly restored on drying. An analysis based on the theory of rubber elasticity leads to the conclusion that chemical degradation is occurring by hydrolysis and chain scission. Gravimetric measurements effected on the polymer exposed to vapour for a fixed time and then dried to (virtual) equilibrium show an increase in weight followed by a decrease and finally a weight loss as exposure time is increased. A theory is proposed to explain the phenomena by initial chemical combination of water followed by leaching of severed chain segments. Calculations of average inter-crosslink molecular weight using both viscoelastic and gravimetric data are in good agreement. It is concluded that long-term exposure of the epoxy adhesive to water leads to both reversible (physical) and irreversible (chemical) degradation of the material.