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<p>Bioepoxy resins offer a sustainable alternative to petroleum-based polymers; however, their intrinsic brittleness restricts their use in structural applications. This study investigates the reinforcing effects of nanobiochar (NBC) and cellulose nanocrystals (CNCs) on the mechanical and thermal properties of bioepoxy composites, with an aim of enhancing fracture toughness. Untreated nanoparticles were pre-dispersed in methanol to improve dispersion prior to incorporation into the bioepoxy. Characterisation included Fourier Transform Infrared Spectroscopy to confirm chemical integrity, Dynamic Light Scattering for particle size distribution, Brunauer‐Emmett‐Teller analysis for surface area, and Scanning Electron Microscopy (SEM) for fracture surface morphology. Rheological analysis assessed dispersion quality, while mechanical performance was evaluated through tensile tests and single-edge notch bending for fracture toughness. Viscoelastic behaviour and glass transition temperature were examined via Dynamic Mechanical Analysis. NBC consistently outperformed CNCs in reinforcing the bioepoxy. At 5&#xa0;wt%, CNCs increased Young’s modulus by 13.6% (3.5 ± 0.2&#xa0;GPa), however, agglomeration at higher loadings reduced effectiveness. NBC (10&#xa0;wt%) achieved a 24.2% increase in Young’s modulus (3.8 ± 0.3&#xa0;GPa) and improved ultimate tensile strength by 9.2% (71 ± 2&#xa0;MPa) at 3&#xa0;wt%. Fracture tests showed that CNCs improved mode I fracture toughness by 37.2% at 3&#xa0;wt% (110 ± 11&#xa0;J&#xa0;m<sup>−2</sup>), whereas NBC produced a 72.7% increase at 7&#xa0;wt% (138 ± 5&#xa0;J&#xa0;m<sup>−2</sup>). SEM analysis revealed mechanisms such as crack pinning and deflection, although voids and agglomerates limited CNC performance. Thermal analysis showed an increase in Tg with nanoparticle addition, reaching 69.1 ± 0.1&#xa0;°C for NBC at 7&#xa0;wt% (5.3% increase). Overall, NBC significantly improved stiffness, strength, fracture toughness, and thermal stability, demonstrating its potential as a high performance, sustainable nanofiller for bioepoxy composites.</p>

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Bioepoxy matrices reinforced with wheat straw-derived nanobiochar (NBC) or cellulose nanocrystals (CNCs)

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月3日

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  • Che L. Grant,
  • Neil A. Williams,
  • Spyridon Koutsonas,
  • Matthew Turner,
  • Ebby Shahidi,
  • Homayoun Hadavinia

摘要

Bioepoxy resins offer a sustainable alternative to petroleum-based polymers; however, their intrinsic brittleness restricts their use in structural applications. This study investigates the reinforcing effects of nanobiochar (NBC) and cellulose nanocrystals (CNCs) on the mechanical and thermal properties of bioepoxy composites, with an aim of enhancing fracture toughness. Untreated nanoparticles were pre-dispersed in methanol to improve dispersion prior to incorporation into the bioepoxy. Characterisation included Fourier Transform Infrared Spectroscopy to confirm chemical integrity, Dynamic Light Scattering for particle size distribution, Brunauer‐Emmett‐Teller analysis for surface area, and Scanning Electron Microscopy (SEM) for fracture surface morphology. Rheological analysis assessed dispersion quality, while mechanical performance was evaluated through tensile tests and single-edge notch bending for fracture toughness. Viscoelastic behaviour and glass transition temperature were examined via Dynamic Mechanical Analysis. NBC consistently outperformed CNCs in reinforcing the bioepoxy. At 5 wt%, CNCs increased Young’s modulus by 13.6% (3.5 ± 0.2 GPa), however, agglomeration at higher loadings reduced effectiveness. NBC (10 wt%) achieved a 24.2% increase in Young’s modulus (3.8 ± 0.3 GPa) and improved ultimate tensile strength by 9.2% (71 ± 2 MPa) at 3 wt%. Fracture tests showed that CNCs improved mode I fracture toughness by 37.2% at 3 wt% (110 ± 11 J m−2), whereas NBC produced a 72.7% increase at 7 wt% (138 ± 5 J m−2). SEM analysis revealed mechanisms such as crack pinning and deflection, although voids and agglomerates limited CNC performance. Thermal analysis showed an increase in Tg with nanoparticle addition, reaching 69.1 ± 0.1 °C for NBC at 7 wt% (5.3% increase). Overall, NBC significantly improved stiffness, strength, fracture toughness, and thermal stability, demonstrating its potential as a high performance, sustainable nanofiller for bioepoxy composites.