Nano-fillers are increasingly incorporated into polymeric materials to improve the mechanical, barrier or other matrix properties of nanocomposites used for consumer and industrial applications. However, over the life cycle, these nanocomposites could degrade due to exposure to environmental conditions, resulting in the release of embedded nanomaterials from the polymer matrix into the environment. This paper presents a rigorous study on the degradation and the release of nanomaterials from food packaging composites. Films of nano-clay-loaded low-density polyethylene (LDPE) composite for food packaging applications were prepared with the spherilene technology and exposed to accelerated weathering of ultraviolet (UV) irradiation or low concentration of ozone at 40 °C. The changes in the structural, surface morphology, chemical and physical properties of the films during accelerated weathering were investigated. Qualitative and quantitative changes in properties of pristine and aged materials and the release of nano-clay proceeded slowly until 130 hr irradiation and then accelerated afterward resulting complete degradation. Although nano-clay increased the stability of LDPE and improved thermal and barrier properties, they accelerated the UV oxidation of LDPE. With increasing exposure to UV, the surface roughness, chemiluminescence index, and carbonyl index of the samples increased while decreasing the intensity of the wide-angle X-ray diffraction pattern. Nano-clay particles with sizes ranging from 2-8 nm were released from UV and ozone weathered composite. The concentrations of released nanoparticles increased with an increase in aging time. Various toxicity tests, including reactive oxygen species generation and cell activity/viability were also performed on the released nano-clay and clay polymer. The released nano-clays basically did not show toxicity. Our combined results demonstrated the degradation properties of nano-clay particle-embedded LDPE composites toxicity of released nano-clay particles to A594 adenocarcinomic human alveolar basal epithelial cells was observed, which will help with future risk based-formulations of exposure.

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评估食品包装聚乙烯-纳米-粘土复合材料的耐候性：纳米颗粒的释放及其影响

纳米填料越来越多地加入聚合物材料中，以改善用于消费和工业应用的纳米复合材料的机械、阻隔或其他基体性能。然而，在整个生命周期中，这些纳米复合材料可能会因暴露于环境条件而降解，导致嵌入的纳米材料从聚合物基质中释放到环境中。本文对食品包装复合材料中纳米材料的降解和释放进行了严格的研究。用球粒技术制备了用于食品包装应用的纳米粘土负载低密度聚乙烯 (LDPE) 复合材料薄膜，并在 40 °C 下暴露于紫外线 (UV) 辐射或低浓度臭氧的加速风化。结构、表面形态的变化，研究了薄膜在加速老化过程中的化学和物理性能。原始和老化材料性质的定性和定量变化以及纳米粘土的释放缓慢进行，直到照射 130 小时，然后加速，导致完全降解。尽管纳米粘土增加了 LDPE 的稳定性并改善了热阻和阻隔性能，但它们加速了 LDPE 的紫外线氧化。随着紫外线照射的增加，样品的表面粗糙度、化学发光指数和羰基指数增加，而广角 X 射线衍射图的强度降低。从紫外线和臭氧风化复合材料中释放出尺寸为 2-8 nm 的纳米粘土颗粒。释放的纳米颗粒的浓度随着老化时间的增加而增加。还对释放的纳米粘土和粘土聚合物进行了各种毒性测试，包括活性氧的产生和细胞活性/活力。释放出来的纳米粘土基本上没有表现出毒性。我们的综合结果证明了纳米粘土颗粒嵌入的 LDPE 复合材料对释放的纳米粘土颗粒对 A594 腺癌人肺泡基底上皮细胞的毒性的降解特性，这将有助于未来基于风险的暴露配方。