Zeolites as effective desiccants to solve hygroscopicity issue of post-consumer mixed recycled polyolefins

The issue addressed in this study concerns the hygroscopicity of post-consumer mixed recycled poly-olefins (PCMP). PCMP commonly incorporate polar contaminants, responsible of their moisture sorption and bad smell; as a consequence, it is necessary to dehumidify the recycled material before processing it. This represents a strong technical limitation, since polyolefin converters are not generally equipped with dehumidification plants, so hindering the future circular economy perspectives for these recycled ma-terials. In order to address this issue, in this study we proposed an easy and innovative solution, alter-native to drying and based on the use, never considered before, of zeolites as desiccant additives during PCMP extrusion. At this regard, we prepared, on a pilot scale extrusion plant, several material formu-lations based on undried PCMP loaded with different amounts and types of zeolites, with and without a compatibilizing agent. The obtained systems were submitted to mechanical tensile test to assess the effectiveness and the technological relevance of the proposed strategy with regard to conventional heat drying and a calcium oxide-based desiccant, specially marketed for processing recycled polyolefins. Results showed that the addition of either type of zeolites at 2 wt% loading has an effective desiccant function during PCMP processing and, with respect to heat drying or calcium oxide desiccant, ensures higher strength of the resultant systems (up to ca. 15% and 40%, respectively). Moreover, the use of the compatibilizing agent improves the mechanical performances until they are a little better than those of the heat dried PCMP. Therefore, in a sustainability perspective of the packaging industry, the proposed strategy can offer a tangible contribution to improve the plastic packaging circularity and to reach the EU plastic recycling targets. (c) 2021 Published by Elsevier Ltd.

Automated summary

This study addresses the hygroscopicity issue of post-consumer mixed recycled poly-olefins (PCMP) and proposes a novel solution using zeolites as desiccant additives during PCMP extrusion. The results show that zeolites can effectively function as desiccants during PCMP processing, ensuring higher strength of the resultant systems compared to traditional drying methods. The use of a compatibilizing agent further improves mechanical performance, offering a tangible contribution to the sustainability of the packaging industry and EU plastic recycling targets.