MultiRec: Effects of multiple extrusion in cast and blown film applications

Abstract

The MultiRec project investigates the degradation of physicochemical and mechanical properties in linear low-density polyethylene granulate subjected to multiple reprocessing cycles without intermediate additivation. This reprocessed granulate is incorporated into stretch films for automatic wrapping. To ensure industry relevance, additional case studies benchmark commercially available virgin films and films with recycled content from MultiRec partners. Two virgin films and two films with 30% post-consumer recyclate (PCR), each 20–24 µm thick, were evaluated. Characterization includes a standard tensile test (ISO 527-3) and a stretch-specific test (ASTM D5459) to assess permanent deformation and stress retention at prestretch values of 200% (safe), 300% (challenging for films with PCR), and 400% (extreme). Transport simulations involve wrapping column-stacked pallets with these films, followed by horizontal shock tests, some preceded by vibrations or exposure to humid, hot conditions, and additional tilt tests at 26°. Video analysis tracks tilting during simulations, while layer displacement is measured before and after. Virgin films have slightly higher maximum stress than films with PCR, with averages of 46.6 ± 4.2 MPa and 45.1 ± 12.7 MPa for virgin films compared to 41.7 ± 1.9 MPa and 40.5 ± 3.1 MPa for films with PCR. No clear trend was observed for strain at break. Prestretch level significantly influences stress retention and permanent deformation, higher prestretch reduces stress retention and increases permanent deformation. Stress retention ranges from 73% at 200% prestretch to 65% at 400%, while permanent deformation ranges from 54% at 200% to 76% at 400%. These findings indicate that commercially available films with recycled content, likely reprocessed only once, have comparable tensile properties to virgin films. The presentation will include transport simulation results and preliminary findings on films with multi-reprocessed granulate compared to these commercial standards.