To increase the use of agricultural residues, such as date palm fibers, for the sustainable reinforcement of biocomposites, this study investigated the incorporation of varying weight percentages of date palm microfibers (DPMF) ranging from 0 wt.% to 10 wt.% into polycaprolactone (PCL) matrix. Biocomposites were fabricated using a combination of compression molding and dry blending techniques with and without sodium hydroxide (NaOH) alkali treatment. The surface modification was found to increase the surface roughness of the fibers, removing impurities such as lignin, hemicellulose, and wax, while improving crystallinity, as evidenced by FTIR, XRD, TGA, and particle size analyses. Among the different biocomposites investigated, the results for 5 wt.% DPMF content biocomposites exhibited the highest tensile properties: approximately 20% increase in tensile strength and 164% increase in Young’s Modulus in comparison to neat PCL. The crystallinity of the matrix exhibited an increasing trend from approximately 39% for neat PCL to 43% for the 5 wt.% DPMF biocomposites. Furthermore, treated biocomposites demonstrated higher water-repellency behavior and improved thermal properties. Dynamic mechanical analysis (DMA) results indicated enhanced storage moduli for alkali-treated composites; at 35 °C, the storage modulus showed approximately 22% increase compared to the untreated DPMF biocomposites, reflecting improved stiffness and thermomechanical performances. This study highlights the potential of DPMF as an efficient, eco-friendly alternative to fossil-based conventional reinforcement for biocomposite materials’ potential for sustainable rigid packaging applications.

Plastic waste causes severe environmental impacts worldwide and threatens the lives of all creatures. In the medical field, most of the equipment, especially personal protective equipment (PPE), is made from single-use plastic. During COVID-19, the usage of PPE has increased, and is disposed of in landfills after being used once. Worldwide, millions of tons of waste syringes are generated from COVID-19 vaccination. A practical alternative to utilizing this waste is recycling it to reinforce building materials. This research introduces an approach to using COVID-19 syringe plastic waste to reinforce building material as composite concrete. Reinforced fiber polymer (FRP) concrete materials were used to mold cylindrical specimens, which underwent mechanical tests for mechanical properties. This study used four compositions with 0%, 5%, 10%, and 15% of FRP to create cylindrical samples for optimum results. Sequential mechanical tests were carried out on the created samples. These specimens were cured for a long period to obtain water absorption capability. After several investigations, the highest tensile and compressive strengths, approximately 2.0 MPa and 10.5 MPa, were found for the 5% FRP composition samples. From the curing test, the lowest water absorbability of around 5% was found for the 5% FRP composition samples.