Abstract The extent to which hydrophilic GO nanofillers regulate polymer degradation during exposure to a combination of ultraviolet (UV) radiation and moisture is presently unknown. Accordingly, this study systematically evaluated the effect of GO on polymer degradability under both humid UV and dry UV conditions. Both GO accumulation at the polymer nanocomposite (PNC) surface and GO release following degradation were also investigated. Different mass loadings of GO were incorporated into waterborne polyurethane (WBPU), a commonly used exterior coating, and the resulting GO/WBPU nanocomposites were exposed to precisely controlled accelerated weathering conditions using the NIST Simulated Photodegradation via High Energy Radiant Exposure (SPHERE) device. Thickness loss and infrared spectroscopy measurements indicated GO slightly improved the durability of WBPU under dry UV conditions but not under humid UV conditions. Raman spectroscopy, scanning electron microscopy, and atomic force microscopy modulus measurements indicated that GO accumulation occurred at and near the PNC surface under both conditions but to a more rapid extent under humid UV conditions. Minimal GO release occurred under dry UV conditions as measured with Raman spectroscopy of aqueous run-off from a simulated rain spray applied to degraded PNCs. In contrast, PNC surface transformations under humid UV conditions suggested that GO release occurred.

中文翻译：

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水分和紫外线对氧化石墨烯/聚合物纳米复合材料降解的影响

摘要 目前尚不清楚亲水性 GO 纳米填料在暴露于紫外线 (UV) 辐射和湿气组合期间对聚合物降解的调节程度。因此，本研究系统地评估了 GO 在潮湿紫外线和干燥紫外线条件下对聚合物降解的影响。还研究了聚合物纳米复合材料 (PNC) 表面的 GO 积累和降解后的 GO 释放。将不同质量负载的 GO 掺入到水性聚氨酯 (WBPU)（一种常用的外墙涂料）中，所得 GO/WBPU 纳米复合材料使用 NIST 模拟光降解通过高能辐射曝光 (SPHERE) 设备暴露于精确控制的加速老化条件下。厚度损失和红外光谱测量表明，GO 在干燥 UV 条件下略微改善了 WBPU 的耐久性，但在潮湿 UV 条件下没有改善。拉曼光谱、扫描电子显微镜和原子力显微镜模量测量表明，在两种条件下，在 PNC 表面和附近都发生了 GO 积累，但在潮湿的紫外线条件下，积累得更快。在干燥的紫外线条件下发生最小的 GO 释放，如使用拉曼光谱测量来自应用于降解 PNC 的模拟雨水喷雾的水性径流。相比之下，潮湿紫外线条件下的 PNC 表面转变表明发生了 GO 释放。和原子力显微镜模量测量表明，在两种条件下，在 PNC 表面和附近都发生了 GO 积累，但在潮湿的紫外线条件下会更快地积累。在干燥的紫外线条件下发生最小的 GO 释放，如使用拉曼光谱测量来自应用于降解 PNC 的模拟雨水喷雾的水性径流。相比之下，潮湿紫外线条件下的 PNC 表面转变表明发生了 GO 释放。和原子力显微镜模量测量表明，在两种条件下，在 PNC 表面和附近都发生了 GO 积累，但在潮湿的紫外线条件下会更快地积累。在干燥的紫外线条件下发生最小的 GO 释放，如使用拉曼光谱测量来自应用于降解 PNC 的模拟雨水喷雾的水性径流。相比之下，潮湿紫外线条件下的 PNC 表面转变表明发生了 GO 释放。