Effects of Bio-Based PP-g-IA Compatibilizer on Polypropylene Composites Incorporating Unmodified and Hydrophobically Modified Lignocellulose

In this study, a bio-based compatibilizer, itaconic acid-grafted polypropylene (PP-g-IA; IP), was synthesized via melt grafting as a sustainable alternative to the conventional petroleum-based maleic anhydride-grafted polypropylene (PP-g-MAH; MP). Successful grafting was confirmed by Fourier-Transform Infrared (FT-IR) spectroscopy, and the efficacy of the synthesized compatibilizer was systematically evaluated by applying it to composites incorporating both unmodified lignocellulose (LC) and hydrophobically modified LC (mLC). Mechanical evaluation revealed that the PP-g-IA-compatibilized LC composite (PPLCIP) achieved the highest tensile strength of 23.5 MPa among all samples. This result is attributed to a synergistic effect: the PP-g-IA compatibilizer significantly improved the interfacial adhesion issue, thereby allowing the intrinsically higher aspect ratio of unmodified LC fibers (3.0 ± 2.1) to serve as the dominant reinforcement factor. While mLC surface modification improved composite performance over unmodified LC even without a compatibilizer, the introduction of a compatibilizer shifted fiber aspect ratio to the dominant factor, resulting in LC-based composites outperforming their mLC-based counterparts. Furthermore, PP-g-IA maintained mechanical performance comparable to that of the conventional PP-g-MAH while simultaneously achieving enhanced melt flowability. These results demonstrate that the bio-based PP-g-IA is an effective and sustainable compatibilization strategy that satisfies both mechanical performance and processability requirements.