Consequences of Humidity Cycling on the Moisture Absorption Characteristics of Epoxy Resins with Different Network Architectures
Consequences of Humidity Cycling on the Moisture Absorption Characteristics of Epoxy Resins with Different Network Architectures
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DOI：
10.1021/acsapm.2c01570
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发表时间：
2023-01
影响因子：
5
通讯作者：
Rishabh D. Guha;E. Danilov;Katherine Berkowitz;Oluwatimilehin E. Oluwajire;L. Grace
中科院分区：
文献类型：
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作者：
Rishabh D. Guha;E. Danilov;Katherine Berkowitz;Oluwatimilehin E. Oluwajire;L. Grace
吸收的水分是在用环氧基聚合物材料性能稳定损失的永久原因。在原子尺度上，交联环氧树脂中单个水分子的状态取决于它们参与的次级键合相互作用的强度和它们的局部物理环境。然而，这些化学和物理变量可以通过改变实验固化时间表在宏观尺度上进行调整。在这项研究中，通过改变环氧树脂：硬化剂组合的化学计量混合比，固化具有不同网络结构的交联环氧树脂基质。随后使样品经受波动的湿度条件，其包括高湿度（> 95%RH）和环境湿度的重复循环。红外（IR）光谱和介电读数都成功地建立了吸湿性，网络形态和介电性能之间的强相关性。在光谱峰分析过程中观察到的异常行为帮助我们理解吸收历史如何在相同的水分浓度下重新分布水物种的浓度。这项研究的结果阐明了吸收现象本身如何作为损伤引发事件，并且它们还表明，样品中不同水物种的空间量化可以使我们能够绘制损伤部位，纳米孔和具有整体较高空隙含量的区域。
Absorbed moisture is a perpetual contributor to the steady loss of performance for in-service epoxy-based polymer materials. On the atomistic scale, the state of individual water molecules in a crosslinked epoxy is dependent on the strength of the secondary bonding interactions they engage in and their local physical environment. However, these chemical and physical variables can be tailored on the macroscopic scale through changes in the experimental curing schedule. In this study, crosslinked epoxy matrices with different network architectures were cured by varying the stoichiometric mixing ratios of the epoxy: hardener combination. The samples were subsequently subjected to fluctuating humidity conditions which comprises repeating cycles of high (∼95% RH) and ambient humidity. Both infrared (IR) spectroscopy and dielectric readings were successful in establishing a strong correlation between moisture absorption, network morphology, and dielectric properties. An anomalous behavior observed during the spectral peak analysis helped us understand how absorption history can redistribute the concentrations of water species at the same moisture concentrations. The results from this study elucidate how the phenomenon of absorption itself can act as a damage initiation event, and they also indicate that the spatial quantification of the different water species across a sample can allow us to map damage sites, nanopores, and areas with an overall higher void content.