Sustainability in rotational molding: a study on recycling and the influence of additives

Abstract The rationale for recycling in the rotational molding community is arguably stronger than other sectors of the polymer industry since the process is more likely to produce extremely large parts and regardless of whether scrap is generated from an end-of-life situation or from off-spec production, this material is often too much and too valuable for diversion to landfill. It is therefore important for the community to establish test methods and knowledge on how to keep these polymeric materials within a circular economy. There is unfortunately little experimental data on recycling by rotomolding for processors to understand the feasibility of reclaiming scrap material in their production, for which this study aims to address. The molded parts of a commercial-grade and reactor-grade polyethylene were examined over several repeated molding cycles, in each case with between 10 and 50 % reclaim content, and then examined for quality indicators based on mechanical and rheological properties, part color and surface void content. The stabilized resin showed negligible changes over four recycle passes, except for yellowness, while the unstabilized resin showed minor signs of change on the second recycle pass. A narrow examination followed to understand the contributions of antioxidants versus UV stabilizers in the performance witnessed in the recycling trials. Overall, the study shows that robust recycling is very possible for the rotational molding industry with polyethylene grades, especially those intended for this process.