Recyclability of Flexible Polyethylene with PP & PA: Novel Findings
RecyClass carried out tests verifying compatibility of common polyethlene (PE) film components with the recycling process. These include polypropylene (PP), polyamide (PA) and ethylene vinyl alcohol (EVOH), each tested at 10% concentration level of the total weight of the film. The results of the testing were used to update the RecyClass Design for Recycling Guidelines for PE Flexible Films for Household and Commercial Packaging enabling further science-based progress in driving design for recycling.
Three, coextruded and unprinted, film samples were tested by Aimplas, an independent laboratory. Each of the film samples contains 90% LDPE and, respectively, 10% PP, PA, and EVOH.
Following the procedures reported in the RecyClass Recyclability Evaluation Protocol for PE films, the samples were first ground and blended with a plain LDPE control sample obtaining a maximum 5% concentration of tested components in the samples, and then extruded. Finally, the pellets were diluted with virgin LDPE obtaining a maximum concentration of PP, PA and EVOH of 2.5% in the samples, and then processed to produce blown films.
The findings of PP testing show that the threshold of 2.5%, of the total weight of the package, increases gels and specks and at the same time decreases tear resistance (-30%) and elongation properties (-24%). The test results, therefore, demonstrate that PP with up to 5% of the total weight of the PE film will have adverse impact on the recycled material.
Additionally, the analysis of copolyamide PA6/66 confirmed the results of the previous findings. Films produced with a 2.5% concentration of copolyamide show a limited increase in haze, as well as in gels and specks. This shows that the compatibilization between PA6/66 and PE can be, to a certain extent, determined by selecting proper tie layers in the film structure.
Finally, the tests carried out on EVOH show that more than 5% EVOH, of the total weight of the PE film, impacts the PE film’s recyclability, confirming the findings of the precedent tests.
When assessing design for recycling and recyclability of packaging, robust and scientifically based benchmarks are key to ensure that the circularity of plastics is not impeded. This is the guiding principle of RecyClass which, up to date, has run several tests on functional barriers both in flexible and rigid applications.
By continuing its research, RecyClass works towards understanding the impacts and at the same time overcoming the possible negative effects of barriers in recycling processes.
 The structure of the tested films is as follows: (1) LDPE/PP/random copolymer/LDPE; (2) LDPE/tie/PA/tie/LDPE; (3) LDPE/tie/EVOH/tie/LDPE
RecyClass is a comprehensive cross-industry initiative that works to advance plastic packaging recyclability and to establish a harmonized approach towards recycled content calculation and traceability in Europe. Activities within RecyClass include the development of Recyclability Evaluation Protocols and scientific testing of innovative materials which serve as the base for the Design for Recycling guidelines and the free online tool. RecyClass offers Recyclability Certifications and Recycled Content Traceability Certification for plastic packaging.