Modifying Mechanical Performance of an <scp>LLDPE</scp> / <scp>PP</scp> Waste Blend During a Single Recycling Cycle Using Organometallic Complexes

ABSTRACT In this study, organometallic complexes were introduced at 0.05 wt% to modify the performance of a 70/30 LLDPE/PP waste blend during a single recycling cycle under high shear. Four complexes (C 8 ‐Ti, C 8 ‐Zr, C 18 ‐Ti, and C 18 ‐Zr), based on Titanium (Ti) or Zirconium (Zr) with phosphate esters of different alkyl chain lengths (P C8 or P C18 ), were incorporated under high‐shear mixing, and their effects on structural, thermal, morphological, and mechanical properties were investigated. Sequential processing of the unmodified waste increased PP crystallinity from 16.1% to 42.7% and reduced total crystallinity from 30.4% to 24.5%, indicating progressive phase separation. Upon additive incorporation, total crystallinity further decreased to 27.9% for C 18 ‐Ti and 29.3% for C 8 ‐Ti, while C 18 ‐Zr showed a slight increase to 35.2%, indicating structure‐dependent effects on phase packing. T _onset values ranged from 409°C to 444°C across all formulations, indicating essentially unchanged thermal stability. Mechanical testing showed that Charpy impact strength increased by up to 50%, rising from 11.3 to approximately 16.7 kJ/m 2 (ISO 179‐1), without detrimental effects on tensile properties, as confirmed by statistical analysis (ANOVA). Fracture analysis indicated that Ti‐containing samples exhibited more fibrillation, whereas Zr‐containing systems showed finer, small‐void fracture surfaces. Overall, the findings demonstrate that these organometallic complexes represent a potentially scalable additive strategy for improving mechanical performance in mixed‐waste polyolefin streams within a single high‐shear recycling cycle.