Determination of Practical and Conservative Extraction Conditions for Recycled High-Density Polyethylene (rHDPE)

The increasing use of post-consumer recycled (PCR) plastics in sensitive packaging applications requires robust approaches for assessing chemical contaminants potentially introduced during previous use and recycling. Safety assessments based on finished packaging, however, can be resource-intensive and may hinder efficient material screening at an early stage. Here, we evaluate a pellet-based migration screening approach for recycled high-density polyethylene (rHDPE) as a potential representative and conservative alternative to testing finished packaging. Gas chromatography–mass spectrometry (GC–MS) was used to characterize substances released from rHDPE pellets into dichloromethane, 95% ethanol, and 50% ethanol under controlled time and temperature conditions. Key substance groups included alkanes and alkenes, fatty acid derivates, phthalates, salicylates, alkyl benzoates and antioxidants. Substance release kinetics were systematically investigated to identify conditions providing a representative or conservative estimate of the release potential. Most substances exhibited comparable release profiles, reaching approximately 85% of their maximum concentrations after 3 days at 40 °C in dichloromethane and after 7 days at 60 °C in ethanol. The outcomes of testing on pellets were subsequently assessed in comparison with testing on corresponding finished rHDPE bottles. For most identifiable substances, pellet testing yielded concentrations comparable to or higher than those measured in bottles, indicating that the approach can adequately capture the substance release potential without requiring production of finished packaging. A limited number of substance-specific deviations were identified and further evaluated; none were considered critical for a typical safety assessment. These findings provide experimental evidence that rHDPE pellets can serve as a representative and generally conservative test material for chemical safety screening of recycled plastics, enabling more efficient material qualification and facilitating the broader use of PCR plastics in contact-sensitive packaging applications.