Date Palm Fiber Agricultural Residue Valorization in Rotationally Molded LLDPE Single- and Multilayered Composites for Engineering Applications

Abstract Waste material valorization in rotational molding is gaining attention for modifying mechanical properties and reducing the use of virgin polymers in plastic components. This study investigated, first of its kind, the use of date palm fibers (DPF), an agricultural residue available abundantly in the Middle East and North Africa region, in linear low-density polyethylene (LLDPE) composites via rotational molding. Roto-molded DPF/LLDPE composites were manufactured with different fiber contents of 5–20 wt % in single-, double-, and triple-layered structures combining only LLDPE and fiber-incorporated LLDPE layers. Double- and triple-layered molding cycles were 10–27% longer than single-layer ones. These multilayered composites showed higher densities compared to single layers, although fiber addition overall reduced composite density. Rheological data and SEM images confirmed good fiber dispersion in the polymer matrix. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses confirmed no changes in crystal structure. DPF addition slowed crystallization, reduced crystallinity and thermal stability compared to only LLDPE samples. The tensile modulus increased by 34–49% in single- and double-layered composites with higher fiber content. However, triple-layered structures demonstrated balanced mechanical performance, retaining a tensile modulus closer to only LLDPE while showing the highest impact strength compared to all composites and even surpassing LLDPE. DPF increased hydrophilicity and thermal insulation in single-layered composites. Double- and triple-layered structures are expected to reduce moisture uptake while further enhancing thermal insulation. These results support the effective valorization of DPF in roto-molded composites, enabling sustainable solutions tailored to specific product performance requirements.