Zepp Richard, Ruggiero Emmanuel, Acrey Brad, Davis Mary J B, Han Changseok, Hsieh Hsin-Se, Vilsmeier Klaus, Wohlleben Wendel, Sahle-Demessie Endalkachew
U.S. Environmental Protection Agency (EPA), Office of Research and Development (ORD), Center for Environmental Measurement and Modeling (CEMM), 960 College Station Rd., Athens, GA, USA.
BASF SE, Dept. Material Physics and Analytics, 67056, Ludwigshafen, Germany.
Environ Sci Nano. 2020;7(6):1742-1758. doi: 10.1039/c9en01360a.
In recent years, an increasing number of polymeric composites incorporating engineered nanomaterials (ENMs) have reached the market. Such nano-enabled products (NEPs) present enhanced performance through improved mechanical, thermal, UV protection, electrical, and gas barrier properties. However, little is known about how environmental weathering impacts ENM release, especially for high-tonnage NEPs like kaolin products, which have not been extensively examined by the scientific community. Here we study the simulated environmental weathering of different polymeric nanocomposites (epoxy, polyamide, polypropylene) filled with organic (multiwalled carbon nanotube, graphene, carbon black) and inorganic (WS, SiO, kaolin, FeO, Cu-phthalocyanines) ENMs. Multiple techniques were employed by researchers at three laboratories to extensively evaluate the effect of weathering: ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), optical microscopy, contact angle measurements, gravimetric analysis, analytical ultracentrifugation (AUC), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy. This work aimed to elucidate the extent to which weathering protocol ( wet dry) and diverse filler characteristics modulate fragment release and polymer matrix degradation. In doing so, it expanded the established NanoRelease protocol, previously used for analyzing fragment emission, by evaluating two significant additions: (1) simulated weathering with rain events and (2) fractionation of sample leachate prior to analysis. Comparing different composite materials and protocols demonstrated that the polymer matrix is the most significant factor in NEP aging. Wet weathering is more realistic than dry weathering, but dry weathering seems to provide a more controlled release of material over wet. Wet weathering studies could be complicated by leaching, and the addition of a fractionation step can improve the quality of UV-vis measurements.
近年来，越来越多含有工程纳米材料（ENM）的聚合物复合材料进入市场。这类纳米功能产品（NEP）通过改善机械、热、紫外线防护、电和气体阻隔性能，呈现出增强的性能。然而，对于环境老化如何影响ENM释放，人们知之甚少，尤其是对于高岭土产品这类高吨位NEP，科学界尚未对其进行广泛研究。在此，我们研究了填充有机（多壁碳纳米管、石墨烯、炭黑）和无机（WS、SiO、高岭土、FeO、铜酞菁）ENM的不同聚合物纳米复合材料（环氧树脂、聚酰胺、聚丙烯）的模拟环境老化情况。三个实验室的研究人员采用了多种技术来广泛评估老化的影响：紫外可见光谱（UV-vis）、傅里叶变换红外光谱（FTIR）、光学显微镜、接触角测量、重量分析、分析超速离心（AUC）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）和拉曼光谱。这项工作旨在阐明老化方案（湿 干）和不同填料特性在多大程度上调节碎片释放和聚合物基体降解。在此过程中，通过评估两个重要补充内容，扩展了先前用于分析碎片排放的既定纳米释放方案：（1）模拟降雨事件的老化和（2）分析前对样品浸出液进行分级分离。比较不同的复合材料和方案表明，聚合物基体是NEP老化中最重要的因素。湿老化比干老化更接近实际情况，但干老化似乎能比湿老化提供更可控的材料释放。湿老化研究可能会因浸出而变得复杂，增加分级分离步骤可以提高UV-vis测量的质量。
