Green and Chemically Synthesized Silver Nanoparticle-Reinforced Coconut Coir Dust/Water-borne Polyurethane Biocomposites for Lightweight Antibacterial Applications
J. Environ. Nanotechnol., Volume 15, No 3 (September 2026) pp. 818-835
Abstract
The present investigation explores a sustainable strategy for utilizing coconut coir dust, a largely underexploited by-product generated from agricultural waste, for the development of lightweight materials. Rather than employing this lignocellulosic waste in conventional low-value applications, the study incorporates environmentally synthesized silver nanoparticles (Ag NPs) into a coconut coir dust-reinforced water-borne polyurethane (WPU) matrix to fabricate functional biocomposites. The optimum formulation was identified using an integrated MEREC–RAFSI multi-criteria decision-making approach. Silver nanoparticles were produced through both chemical reduction and green synthesis routes utilizing lemon peel extract as a stabilizing and reducing agent. Structural, morphological, thermal, and antibacterial characteristics of the developed composites were systematically evaluated using XRD, FTIR, FESEM, thermogravimetric analysis (TGA), UV–Visible spectroscopy, and dynamic light scattering (DLS). The results confirmed the successful formation and homogeneous dispersion of Ag nanoparticles throughout the polymer matrix. DLS analysis revealed average particle sizes of approximately 55 nm and 61 nm for chemically synthesized and green-synthesized Ag nanoparticles, respectively, while XRD analysis indicated crystallite sizes of 21.0 and 20.84 nm. Mechanical evaluation demonstrated notable improvements in performance, with tensile strength values ranging from 22.4 ± 1.0 to 26.4 ± 0.4 MPa, tensile modulus from 31.2 ± 1.1 to 42.2 ± 0.4 MPa, and excellent flexing durability exceeding 8400 cycles, confirming suitability for lightweight applications. Furthermore, antibacterial assessment indicated strong inhibitory activity against both Bacillus subtilis and Escherichia coli, with the G4 composite exhibiting inhibition zones of 15.3 mm and 14.2 mm, respectively. The developed biocomposite therefore represents a promising eco-friendly alternative to conventional materials, combining waste valorization, enhanced mechanical integrity, thermal stability, and effective antibacterial functionality.
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