Closed-Loop Recycling of ELV Fuel-Tank HDPE: Multimodal Characterization and Processability at High Recycled Content

This study evaluates the technical and environmental viability of reinserting post-consumer high-density polyethylene (rPE) recovered from end-of-life vehicle (ELV) multilayer fuel tanks into blow-moulding–grade blends. Virgin tank-grade HDPE was compounded with 50, 75, and 90 wt% rPE and assessed by multimodal characterization, including thermal and molecular analyses, AFM/SEM morphology, tensile/flexural/impact testing, linear viscoelasticity, capillary rheology, and uniaxial extensional rheology. All blends displayed viscoelastic and capillary flow behaviour comparable to the virgin grade and showed consistent strain hardening across compositions. The 90 wt% rPE / 10 wt% virgin blend maintained melt strength and mechanical performance after up to ten extrusion cycles, with only minor microstructural refinement and no measurable deterioration of bulk properties. A cradle-to-gate mini–life cycle assessment (per 1 kg compound) indicates substantial climate benefits, corresponding to approximately 1.2–1.5 kg CO 2 e avoided per kg for the 90 wt% rPE formulation (depending on the electricity mix). Overall, the results show that very high recycled content can be achieved without compromising processability or stability, thereby supporting circular economy strategies for automotive polymers. • ELV fuel-tank rHDPE blended up to 90 wt% with virgin tank-grade HDPE • Strain hardening retained in all blends, supporting blow molding processability • 10 extrusion cycles showed stable mechanics and rheology for the 10:90 blend • GPC-IR confirms overlapping MWD and near-constant short-chain branching • Washing plus vented extrusion reduces fuel VOCs in the most contaminated stream