Chemical Engineering Department, University of Alicante, San Vicente del Raspeig Road, s/n, 03690 San Vicente del Raspeig, Alicante, Spain.
Sci Total Environ. 2021 Mar 1;758:144066. doi: 10.1016/j.scitotenv.2020.144066. Epub 2020 Nov 26.
While the annual European demand for polyolefins is 25 million tonnes, only 3 million tonnes of recycled polyolefins find their place in the market, despite collecting 15 million tonnes of post-consumer polyolefins every year. Brand owners of care products are showing their interest in using post-consumer recycled plastics for their packaging. However, there is a general concern in using these materials, as recycled polymers can contain unwanted substances that may expose the consumer to health risks or make the packaging unattractive. Accordingly, the presence of these contaminants narrows the market opportunity of recycled plastics to applications with low-quality requirements and in which the product is not in direct contact with the consumer. Though mechanical recycling is the most widespread solution presents limitations in terms of decontamination, as only superficial substances are removed. Thereby, the volatile organic compounds (VOCs) migrated to the polymer matrix remain inside. Consequently, there is a need to find a solution to purify recycled plastics and increase their market share. This study focuses on removing VOCs from post-consumer recycled HDPE through two innovative methods applied for the first time in this field, steam stripping and polyethylene glycol (PEG) extraction. The methodology implemented to analyze the volatile organic compounds in HDPE was HS-SPME-GC/MS. Both methods showed a decrease above 70% in the VOCs content compared to extrusion-degassing. Moreover, these were compared to hot air stripping, a new technology developed at an industrial scale for the removal of VOCs. As a result, steam stripping improved efficiency in reducing the overall VOCs compared to hot air stripping. The PEG extraction method lowered the volatile polar compounds further than using hot air stripping. Additionally, none of these technologies modified the HDPE melting flow index.
虽然欧洲每年对聚烯烃的需求为 2500 万吨，但尽管每年回收 1500 万吨消费后的聚烯烃，市场上仍只有 300 万吨回收聚烯烃。护理产品的品牌所有者对使用消费后回收塑料用于其包装表现出兴趣。然而，人们普遍担心使用这些材料，因为回收聚合物可能含有不需要的物质，可能使消费者面临健康风险或使包装失去吸引力。因此，这些污染物的存在将回收塑料的市场机会缩小到对质量要求较低的应用领域，以及产品与消费者不直接接触的应用领域。虽然机械回收是最广泛的解决方案，但在去污方面存在限制，因为只能去除表面物质。因此，迁移到聚合物基质中的挥发性有机化合物 (VOC) 仍留在内部。因此，需要找到一种方法来净化回收塑料并增加其市场份额。本研究专注于通过两种创新方法从消费后回收高密度聚乙烯 (HDPE) 中去除 VOC，这两种方法在该领域首次应用。该方法采用 HS-SPME-GC/MS 分析 HDPE 中的挥发性有机化合物。与挤出脱气相比，这两种方法都显示出 VOC 含量降低了 70%以上。此外，还将它们与热空气汽提进行了比较，热空气汽提是一种在工业规模上开发用于去除 VOC 的新技术。结果表明，与热空气汽提相比，蒸汽汽提在降低总体 VOC 方面的效率更高。PEG 萃取法比使用热空气汽提进一步降低了挥发性极性化合物的含量。此外，这些技术都没有改变 HDPE 的熔融流动指数。
