The use of the polypropylene (PP) recyclates in certain processing methods and applications is still limited by their quality. The high melt flow rate (MFR) and the inconsistent properties of recyclates are common obstacles to their use. Therefore, this work aims to identify possible reasons for the low and inconsistent quality of PP recyclates depending on the source material in PP waste bales. The levels of polymeric and non-polymeric contaminants were assessed. As mixing of different PP grades is an issue for the MFR, the proportions of the different processing grades were also investigated and the potential of sorting by processing method to produce lower MFR recyclates was assessed. The analysis showed that the waste bales, although pre-sorted, still contained high amounts of contaminants. Injection moulding was found to be the predominant processing method in the bales, explaining the high MFR of PP recyclates. However, a sufficiently high amount of low MFR products was found in the bales, which seems promising for the production of low MFR recyclates. Seasonal variations in the composition of the waste bales were identified as one of the reasons for the inconsistent qualities of recyclates. These results highlight the importance of proper sorting and treatment of PP waste bales prior to reprocessing in order to obtain high-quality recycled products.

中文翻译：

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不同聚丙烯废包的分析：PP 回收原料的评估

聚丙烯 (PP) 回收材料在某些加工方法和应用中的使用仍然受到其质量的限制。回收材料的高熔体流动速率 (MFR) 和不一致的性能是其使用的常见障碍。因此，这项工作的目的是根据 PP 废包的来源，确定 PP 回收品质量低下且不一致的可能原因。评估了聚合物和非聚合物污染物的水平。由于不同聚丙烯等级的混合对于 MFR 来说是一个问题，因此还研究了不同加工等级的比例，并评估了按加工方法分选生产较低 MFR 回收料的潜力。分析显示，废物包虽然经过预先分类，但仍然含有大量污染物。研究发现注塑成型是捆包的主要加工方法，这解释了 PP 回收材料的高 MFR。然而，在捆包中发现了足够多的低 MFR 产品，这对于低 MFR 回收材料的生产似乎很有希望。废物包成分的季节性变化被认为是回收材料质量不一致的原因之一。这些结果凸显了在再加工之前对聚丙烯废料包进行适当分类和处理的重要性，以获得高质量的回收产品。