Effect of Extrusion Reprocessing on the Thermal, Mechanical, and Morphological Properties of Olive Pomace‐Reinforced Polypropylene Composites

Plastic recycling and the valorization of waste‐derived fillers have become increasingly important for the development of sustainable polymer materials. In this study, polypropylene (PP) composites reinforced with olive pomace (P) were produced, and the effects of repeated thermomechanical reprocessing (C1–C6) on their mechanical, thermal, and structural properties were investigated. The PP‐P composites were fabricated using a twin‐screw extruder followed by hot pressing. Differential scanning calorimeter (DSC) thermograms revealed that the crystallinity in the PP‐P‐C6 sample increased by 31.4% compared to neat PP, and the melting ( T m ) and crystallization temperatures ( T c ) rose to 163.12 and 122.5, respectively. Thermal analysis revealed that although the initial decomposition temperatures ( T 5% ) were lowered due to the lignocellulosic structure of P, T max values were largely maintained throughout the extrusion cycles (C1–C6). Compared to neat PP, the PP‐P composites exhibited pronounced improvements in flexural properties, and these enhancements were maintained throughout the extrusion cycles. The flexural strength (FS) values ranged from 45.5 to 52.8 MPa, while the flexural modulus (FMOE) values varied between 1541.8 and 1936.2 MPa. These findings demonstrate that PP‐P systems preserve their mechanical and thermal properties across successive recycling cycles (C1–C6), without a significant deterioration in performance.