Light‐Weight Sustainable Composite From Virgin and Recycled Polypropylene Blends and Biocarbon for Automotive Part Application

This work develops lightweight, sustainable PP/rPP/biocarbon composites targeting automotive applications. Virgin PP was blended with automotive recycled PP (rPP) at 70/30 and 50/50 ratios; the 50PP/50rPP blend exhibited the highest impact strength (31.54 J/m) with acceptable stiffness and was selected as the composite matrix. Incorporation of 24 wt% waste paper/plastic‐derived biocarbon (BC) and 3 wt% PP‐g‐MA (MAPP) into the 50/50 blend increased tensile and flexural moduli by 36% and 33%, while maintaining density below 1.0 g/cm 3 (0.977 g/cm 3 ), thus maintaining a favorable stiffness‐to‐weight ratio. Thermal stability was significantly improved: T 10 increased by 33°C in the compatibilized BC composite compared to the 50PP/50rPP blend, and HDT increased by 44%. Biocarbon acted as a nucleating agent, increasing crystallinity by 47% in the uncompatibilized composite. The Guth‐Smallwood model predicted a nearly two‐fold increase in tensile and flexural moduli at a BC volume fraction of 0.19; experimentally, the BC composites reached ~67%–82% of this theoretical upper bound, indicating effective but non‐ideal reinforcement due to residual agglomeration and interfacial defects. The PP/rPP/BC system demonstrates low‐density, high stiffness, thermally stable composites suitable for automotive components such as dashboards while valorizing waste streams and reducing dependence on virgin fossil‐based polymers.