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<p>In this study, carbon quantum dots (CQDs) based on weathered coal were synthesized by green oxidation method. Then, polylactic acid (PLA) nanocomposites foams were prepared with CQDs by a supercritical CO<sub>2</sub> autoclave foaming process. Moreover, the impact of CQDs on the mechanical strength, pore density, and foaming rate of PLA was investigated, respectively. Under the optimum circumstances of a melting temperature of 180&#xa0;°C, a melting time of 3&#xa0;h, a pressure of 11.7&#xa0;MPa, a foaming temperature of 120&#xa0;°C, and a foaming time of 1&#xa0;h, the foam expansion rate reached roughly 64.92 times. Still, the foaming ratio of pure PLA was only 36.13 times. By adjusting various parameters, the crystallinity of the PLA/CQDs nanocomposites foam was enhanced from 21.38% (pure PLA foam) to 46.7%, and its compressive stress was increased from 78 to 224&#xa0;kPa, resulting in high mechanical properties and the foaming performance of PLA/CQDs due to the high specific surface area of CQDs. Molecular dynamics simulations analysed the mean displacement of CO₂ molecules within pure PLA molecules and PLA/CQDs nanocomposite foamed materials, yielding diffusion coefficients D of 4.49 × 10⁻<sup>2</sup> Å<sup>2</sup>/Ps and 2.794 × 10⁻<sup>2</sup> Å<sup>2</sup>/Ps respectively. The incorporation of CQDs promotes strong interactions between CQDs and CO₂ molecules, enabling more controllable regulation of CO₂ molecular diffusion rates and enhancing CO₂ solubility within PLA/CQDs composite nano-foamed materials. This approach achieves high foaming ratios while improving the crystallinity and melt strength of PLA.</p>

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Preparation of polylactic acid/carbon quantum dots based on weathered coal and their foaming performance under supercritical CO₂

  • 期刊论文

  • 发表日期：

    2026年2月19日

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  • Shuai Liu,
  • Qianjin Xiang,
  • Weijun Zhen

摘要

In this study, carbon quantum dots (CQDs) based on weathered coal were synthesized by green oxidation method. Then, polylactic acid (PLA) nanocomposites foams were prepared with CQDs by a supercritical CO2 autoclave foaming process. Moreover, the impact of CQDs on the mechanical strength, pore density, and foaming rate of PLA was investigated, respectively. Under the optimum circumstances of a melting temperature of 180 °C, a melting time of 3 h, a pressure of 11.7 MPa, a foaming temperature of 120 °C, and a foaming time of 1 h, the foam expansion rate reached roughly 64.92 times. Still, the foaming ratio of pure PLA was only 36.13 times. By adjusting various parameters, the crystallinity of the PLA/CQDs nanocomposites foam was enhanced from 21.38% (pure PLA foam) to 46.7%, and its compressive stress was increased from 78 to 224 kPa, resulting in high mechanical properties and the foaming performance of PLA/CQDs due to the high specific surface area of CQDs. Molecular dynamics simulations analysed the mean displacement of CO₂ molecules within pure PLA molecules and PLA/CQDs nanocomposite foamed materials, yielding diffusion coefficients D of 4.49 × 10⁻2 Å2/Ps and 2.794 × 10⁻2 Å2/Ps respectively. The incorporation of CQDs promotes strong interactions between CQDs and CO₂ molecules, enabling more controllable regulation of CO₂ molecular diffusion rates and enhancing CO₂ solubility within PLA/CQDs composite nano-foamed materials. This approach achieves high foaming ratios while improving the crystallinity and melt strength of PLA.