<p>This study investigated the effect of adding nanodiamonds to blends of poly(L-lactic acid) (PLLA) and ethylene–vinyl acetate copolymer (EVA) prepared using the melt-compounding method. The PLLA used in this study has a crystallization temperature of 112&#xa0;°C, and the EVA as an amorphous polymer exhibits a glass transition around 30&#xa0;°C during the cooling process. Because the PLLA crystallization behavior was affected by the mixing ratio, the PLLA/EVA blends did not appear to form completely phase-separated systems. A PLLA:EVA ratio of 3:1 in the blend alleviates the brittleness of PLLA and the low Young’s modulus of EVA. It also demonstrated optimal mechanical properties, combining a steep stress–strain curve rise with enhanced elongation from 5 to 20%. Nanodiamond particles added to the PLLA/EVA blends were found to selectively penetrate the amorphous phase of EVA and disperse in relatively small amounts in the PLLA phase. In the PLLA/EVA/nanodiamond ternary composites, although the degree of crystallization of the PLLA part decreases slightly, the PLLA/EVA blend shows an increase in the Young’s modulus and maximum stress value. Furthermore, the properties in the elongation direction are maintained although they decrease, suggesting a reduction in the inherent brittleness of PLLA. The incorporation of 15 wt% nanodiamonds into the 3:1 PLLA/EVA blend doubled the maximum stress and achieved a high Young’s modulus of 1242&#xa0;MPa, comparable to neat PLLA, while maintaining an improved elongation rate of 10%.</p> Graphical abstract <p></p>

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Preparation, structural estimation, and mechanical properties of poly(L-lactide)/ethylene–vinyl acetate blends and the effect of nanodiamond addition

  • Rokibul Hasan Rumon,
  • Chisato Nara,
  • Yuya Matsuo,
  • Kai Xu,
  • Atsuhiro Fujimori

摘要

This study investigated the effect of adding nanodiamonds to blends of poly(L-lactic acid) (PLLA) and ethylene–vinyl acetate copolymer (EVA) prepared using the melt-compounding method. The PLLA used in this study has a crystallization temperature of 112 °C, and the EVA as an amorphous polymer exhibits a glass transition around 30 °C during the cooling process. Because the PLLA crystallization behavior was affected by the mixing ratio, the PLLA/EVA blends did not appear to form completely phase-separated systems. A PLLA:EVA ratio of 3:1 in the blend alleviates the brittleness of PLLA and the low Young’s modulus of EVA. It also demonstrated optimal mechanical properties, combining a steep stress–strain curve rise with enhanced elongation from 5 to 20%. Nanodiamond particles added to the PLLA/EVA blends were found to selectively penetrate the amorphous phase of EVA and disperse in relatively small amounts in the PLLA phase. In the PLLA/EVA/nanodiamond ternary composites, although the degree of crystallization of the PLLA part decreases slightly, the PLLA/EVA blend shows an increase in the Young’s modulus and maximum stress value. Furthermore, the properties in the elongation direction are maintained although they decrease, suggesting a reduction in the inherent brittleness of PLLA. The incorporation of 15 wt% nanodiamonds into the 3:1 PLLA/EVA blend doubled the maximum stress and achieved a high Young’s modulus of 1242 MPa, comparable to neat PLLA, while maintaining an improved elongation rate of 10%.

Graphical abstract