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<p>Mechanical recycling of polyamide 66 (rPA66) represents a promising strategy to enhance material circularity in engineering plastics. However, repeated thermal and hydrolytic degradation induces severe chain scission, leading to reduced molecular weight, and deterioration of mechanical and rheological properties. To overcome these limitations, epoxy-functional chain extenders (CEs) composed of styrene, methyl methacrylate (MMA), and glycidyl methacrylate (GMA) are synthesized and applied to rPA66 via reactive extrusion at concentrations of 1, 3, and 5 parts per hundred resin (phr). Torque rheometry and oscillatory shear measurements reveal significant increases in melt viscosity and elasticity, confirming effective chain rebuilding and the formation of long-chain branched architectures. Differential scanning calorimetry shows that low extender contents slightly enhance crystallization temperature and crystallinity due to heterogeneous nucleation, whereas higher loadings lead to decreases in melting and crystallization temperatures as a result of restricted chain mobility. Tensile testing demonstrates pronounced improvements in elongation at break and toughness with increasing extender content, particularly for rPA66/ADR. Notably, the incorporation of 3–5 phr ADR results in more than a threefold increase in elongation compared to neat rPA66 while maintaining acceptable tensile strength. However, the higher reactivity of ADR causes greater disruption of crystallization, leading to a lower modulus relative to the synthesized CE at equivalent loadings. Consequently, this study highlights the critical role of chain extender architecture in balancing stiffness, toughness, and processability for upgrading rPA66.</p> Graphical abstract <p>Chain extension of rPA66 using as-synthesized random copolymer type epoxy-functional chain extender enables improved rheological and mechanical properties.</p>

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Effect of epoxy-functional chain extender architecture on the rheological, thermal, and mechanical properties of recycled polyamide 66

  • 期刊论文

  • 发表日期：

    2026年4月27日

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  • Dae Kyom Kim,
  • Sihyeon Ahn,
  • Eunju Noh,
  • Youngjae Yoo

摘要

Mechanical recycling of polyamide 66 (rPA66) represents a promising strategy to enhance material circularity in engineering plastics. However, repeated thermal and hydrolytic degradation induces severe chain scission, leading to reduced molecular weight, and deterioration of mechanical and rheological properties. To overcome these limitations, epoxy-functional chain extenders (CEs) composed of styrene, methyl methacrylate (MMA), and glycidyl methacrylate (GMA) are synthesized and applied to rPA66 via reactive extrusion at concentrations of 1, 3, and 5 parts per hundred resin (phr). Torque rheometry and oscillatory shear measurements reveal significant increases in melt viscosity and elasticity, confirming effective chain rebuilding and the formation of long-chain branched architectures. Differential scanning calorimetry shows that low extender contents slightly enhance crystallization temperature and crystallinity due to heterogeneous nucleation, whereas higher loadings lead to decreases in melting and crystallization temperatures as a result of restricted chain mobility. Tensile testing demonstrates pronounced improvements in elongation at break and toughness with increasing extender content, particularly for rPA66/ADR. Notably, the incorporation of 3–5 phr ADR results in more than a threefold increase in elongation compared to neat rPA66 while maintaining acceptable tensile strength. However, the higher reactivity of ADR causes greater disruption of crystallization, leading to a lower modulus relative to the synthesized CE at equivalent loadings. Consequently, this study highlights the critical role of chain extender architecture in balancing stiffness, toughness, and processability for upgrading rPA66.

Graphical abstract

Chain extension of rPA66 using as-synthesized random copolymer type epoxy-functional chain extender enables improved rheological and mechanical properties.