One step closer to circularity: recycling post-consumer PE-HD into shampoo bottles

Abstract

Due to their dominance in the extrusion blow-moulded plastic packaging, post-consumer PE-HD bottles pose a promising material stream for increasing current recycling rates. Several studies already considered the circularity potential of PE-HD post-industrial milk bottles as well as material from multicoloured post-consumer waste streams and highlighted the addition of virgin resins to enhance the properties of these materials. However, little is known about the baseline performance of current, multicoloured post-consumer PE-HD (rPE-HD) and its suitability for blow-moulding. Consequently, a cold-washed batch of rPE-HD from the Austrian source separated waste collection system was obtained, granulated and extrusion blow-moulded at industrial scale. The corresponding flakes, regranulate pellets and produced bottles were investigated to gain insights on the recycling feedstock and impacts of melt processing on material performance. The collected samples underwent comprehensive laboratory-scale analysis including flake composition via infrared spectroscopy, thermal analysis via DSC and TGA, rheological shear and extension experiments, energy dispersive x-ray (EDX) scans of cryo-fractured tensile specimens, regular tensile tests as well as bottle drop- and strain hardening behaviour assessments. The obtained results demonstrated that extrusion blow-moulding grade rPE-HD can be successfully converted into recycled bottles, yet remains an underutilised feedstock for mechanical recycling. Despite containing ~ 4 wt% of PP contamination, the extrusion blow-moulded rPE-HD bottles exhibit high ductility in the side wall regions (> 1000%) and drop resistance from a height of 0.8 m. However, to realise the “100% rPE-HD bottle” at scale, the cooperation of all value cycle participants is much-needed.