Managing challenging waste fractions: Mechanical recycling of PP/TPV blends from automotive post-industrial waste

Post-industrial waste from automotive window-profile production combines polypropylene (PP) copolymer, thermoplastic vulcanizate (TPV), high-density polyethylene (HDPE), residual aluminium and acrylate foam adhesive in a co-extruded assembly that poses challenges for mechanical recycling. We compared three mechanical recycling routes of increasing process complexity — direct regranulation, melt filtration with vacuum degassing, and melt filtration with vacuum degassing and nitrogen inerting — and used a virgin PP/TPV blend study and SEM fracture-surface analysis to identify the property-limiting factor. Adding purification steps tended to raise the tensile modulus slightly, but tensile strength at yield and Charpy notched impact strength were essentially unchanged across all three routes. None of the routes lifted the recyclate into the property range typical of PP-based bumper applications. The virgin PP/TPV blend series reproduced the recyclate property level at the same nominal TPV content, and the SEM micrographs showed a morphology dominated by TPV pull-out cavities whose density scaled with TPV content. These results indicate that for recyclate performance appears to be the elastomer fraction in the blend itself, not the residual contamination after filtration. Diluting the effective TPV content below 5 wt.% by blending the recyclate with virgin PP recovered stiffness and strength within the bumper-recyclate range, while impact strength stayed below virgin-PP levels. A life cycle assessment (EF 3.1) showed that this recycling-plus-blending route delivers net-negative environmental impacts when the blend substitutes virgin PP, with the benefit growing as extrusion throughput scales up. The practical lever for higher recyclate quality lies upstream — in component formulation and seal design — not in increasingly elaborate downstream purification.