Abstract
This study presents a novel approach to the thermo-mechanical performance of unsaturated polyester resin (UPR) composites reinforced with hybrid biomass fillers made from carboxymethyl cellulose (CMC) and date palm fronds (DPF). For the first time, this work systematically investigates the synergistic reinforcement effect of untreated DPF (agricultural waste) combined with CMC in a thermosetting polyester matrix. The mechanical and thermal properties of the composites were assessed after fabricating with filler loadings of 10, 15, and 20 wt%. The most balanced improvement was observed in the 20% hybrid formulation. In comparison to neat UPR, this composition produced a improvement in tensile strength (reaching 35.87 MPa) as well as a 33% increase in hardness (96.8 Shore D) and a 70% increase in compressive strength, which reached 85.75 MPa. Better heat transfer characteristics were indicated by a 66% improvement in thermal conductivity, which reached 0.690 W/m·K. Fourier transform infrared (FTIR) spectroscopy confirmed strong interfacial adhesion between the fillers and the matrix through the presence of characteristic peaks (e.g., C = O stretching at 1720 cm−1 and C-O at 1117–1122 cm−1) with shifts indicating hydrogen bonding, which helps explain the observed mechanical enhancement. Unlike previous studies that used single fillers or chemically treated fibers, these results demonstrate the potential of DPF/CMC hybrid composites as high-performance, environmentally friendly materials. This study provides useful information for development of polymer composites that efficiently use agricultural waste resources and possess optimal thermo-mechanical qualities for industrial applications. These findings provide practical recommendations for composite formulation by clearly demonstrating the distinct relationships between filler content and material performance.
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