Performance enhancement of unsaturated polyester using sustainable CaCO₃ nanoparticles: A multiscale characterization study

Abstract

In this study, unsaturated polyester (UPE) composites reinforced with oyster/shell-derived CaCO₃ nanoparticles (OSP) were fabricated with filler loadings of 1, 3, 5, 7, and 9 wt.% to evaluate their structural, mechanical, thermal, morphological, and antibacterial properties. Composite density increased from 1.20 g/cm³ (0%) to 1.30 g/cm³ (9%), confirming effective nanoparticle incorporation. XRD analysis showed enhanced calcite peak intensity with increasing OSP content, while crystallite size increased from 27.0 nm (1%) to 30.0 nm (7%). AFM results demonstrated a significant reduction in surface roughness, reaching 0.418 nm at 9 wt.%. FESEM images confirmed uniform dispersion at 5–7 wt.% and agglomeration at higher contents. Mechanical performance improved markedly, with optimal tensile (13.896 MPa), flexural (81.9 MPa), hardness (85.1 Shore D), impact strength (9.08 kJ/m²), and thermal conductivity (0.441 W/m·°C) observed at 5–7 wt.%. Antibacterial tests showed strong inhibition against E. coli and S. aureus, with complete E. coli elimination at 7 wt.%.