Mechanical, morphological, rheological, and water absorption performances of recycled-polyvinyl chloride/styrene-co-acrylonitrile blend composites incorporating fiber from treated date palms

Recent research has focused on the use of natural fiber/recycled plastic composites for industrial waste recycling and the reduction of environmental pollution. This study examines the development of recycled polyvinyl chloride-styrene-co-acrylonitrile copolymer blend (rPVC-SAN) filled with date palm fiber (DF). The composites were produced using a co-rotating twin-screw micro-extruder at processing temperatures ranging from 165 to 175°C, followed by hot compression molding at 170°C under a pressure of 300 bar for 10 min. The impact of fiber surface modification (alkali and silane treatments) on the mechanical, morphological, and water absorption properties of the composites was investigated. The rPVC-SAN-DF composites exhibited superior interfacial characteristics following surface treatment. Then, the impact of DF surface treatment on composite characteristics was assessed. In addition, the adhesion of rPVC-SAN-DF composites after various treatments was investigated. Due to its strong interfacial interaction and the interaction involving the alkoxy group of silane coupling agents and the nitrile group in SAN, the combined alkali-silane composite (BC-NaSi) outperformed other composites in mechanical properties. This resulted in the SAN accumulating at the interface between components and diminished the hydrophilicity of DF. Specifically, compared to the untreated composite, the BC-NaSi composite exhibited maximum improvements of 30% in tensile strength, 40% in tensile modulus, 24% in flexural strength, and 38% in flexural modulus. Scanning electron micrographs (SEM) revealed that the BC-NaSi composite has a rough surface with many exposed fibers, supporting the hypothesis that alkali-silane-treated fibers may improve interfacial bonding. The rheological properties of the composites were tested using dynamic shear rheology. The treated fiber composite demonstrated improved rheology. At low frequencies both the complex viscosity (3.06 × 10 ⁵  Pa. s) and the storage modulus (13.24 GPa) were increased in the BC-NaSi composite. Finally, the water uptake performance of the composites was studied. After 2, 4, and 6 weeks, the BC-NaSi composite still had the lowest water uptake at 4.02%, 4.22%, and 4.37%, respectively. The results illustrate the potential of using agricultural waste fibers in recycled polymer composites to produce sustainable materials with enhanced performance for structural, electrical, and packaging applications.