Goodwin David G, Lai Trinny, Lyu Yadong, Lu Chen Yuan, Campos Alejandro, Reipa Vytas, Nguyen Tinh, Sung Lipiin
National Institute of Standards and Technology, Materials and Structural Systems Division, Engineering Laboratory, Gaithersburg, MD 20899 USA.
National Institute of Standards and Technology, Biosystems and Biomaterials Division, Materials Measurement Laboratory, Gaithersburg, MD 20899 USA.
NanoImpact. 2020;19. doi: 10.1016/j.impact.2020.100249.
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.
目前尚不清楚亲水性氧化石墨烯（GO）纳米填料在暴露于紫外线（UV）辐射和湿气的组合环境下对聚合物降解的调节程度。因此，本研究系统地评估了在潮湿紫外线和干燥紫外线条件下，GO对聚合物降解性的影响。同时还研究了聚合物纳米复合材料（PNC）表面的GO积累情况以及降解后的GO释放情况。将不同质量负载的GO掺入常用的外墙涂料水性聚氨酯（WBPU）中，并使用美国国家标准与技术研究院（NIST）的高能辐射暴露模拟光降解（SPHERE）装置，将所得的GO/WBPU纳米复合材料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在干燥紫外线条件下略微提高了WBPU的耐久性，但在潮湿紫外线条件下则没有。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，GO都在PNC表面及附近积累，但在潮湿紫外线条件下积累速度更快。通过对降解后的PNC进行模拟雨喷雾的水性径流拉曼光谱测量，发现在干燥紫外线条件下GO释放极少。相比之下，潮湿紫外线条件下PNC表面的变化表明发生了GO释放。
