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<p>The rheological evolution of multiple-recycled polyethylene terephthalate (rrPET) modified with a multifunctional epoxide-based chain extender (Joncryl ADR 4468) was systematically investigated under controlled thermal and temporal conditions. Oscillatory and capillary rheometer, combined with network elasticity and phenomenological constitutive models, were employed to elucidate the mechanisms of chain extension and entanglement formation in degraded rrPET. The addition of 0.4 wt% chain extender increased the intrinsic viscosity from 0.376 to 0.596 dL/g and the number-average molecular weight from 6009 to 11087.5&#xa0;g/mol. Rheological analysis confirmed shear-thinning flow, measurable yield stress, and enhanced complex viscosity. Arrhenius evaluation revealed a reduction in activation energy for viscous flow (from 103.9 to 87.3&#xa0;kJ/mol), indicating improved thermal stability. Time-resolved SAOS experiments at 275&#xa0;°C demonstrated progressive growth of network elasticity, with entanglement density rising from 6.6 to 24.4&#xa0;mol/m³, consistent with rubber elasticity predictions. Integration of Boltzmann superposition, classical elasticity, and Mooney–Rivlin modeling provided a coherent mechanistic framework linking chain-extension reactions to macroscopic viscoelastic reinforcement. These findings highlight the critical role of controlled reactive rheology in restoring melt integrity of rrPET and provide a fundamental basis for understanding the interplay of degradation, chain extension, and network formation in branched polyesters.</p>

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Rheology of Chain Extended Multiple-Recycled PET for Fiber Spinning

  • 期刊论文

  • 发表日期：

    2026年5月24日

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  • K. Heydari,
  • A. Zadhoush,
  • A. A. Yousefi

摘要

The rheological evolution of multiple-recycled polyethylene terephthalate (rrPET) modified with a multifunctional epoxide-based chain extender (Joncryl ADR 4468) was systematically investigated under controlled thermal and temporal conditions. Oscillatory and capillary rheometer, combined with network elasticity and phenomenological constitutive models, were employed to elucidate the mechanisms of chain extension and entanglement formation in degraded rrPET. The addition of 0.4 wt% chain extender increased the intrinsic viscosity from 0.376 to 0.596 dL/g and the number-average molecular weight from 6009 to 11087.5 g/mol. Rheological analysis confirmed shear-thinning flow, measurable yield stress, and enhanced complex viscosity. Arrhenius evaluation revealed a reduction in activation energy for viscous flow (from 103.9 to 87.3 kJ/mol), indicating improved thermal stability. Time-resolved SAOS experiments at 275 °C demonstrated progressive growth of network elasticity, with entanglement density rising from 6.6 to 24.4 mol/m³, consistent with rubber elasticity predictions. Integration of Boltzmann superposition, classical elasticity, and Mooney–Rivlin modeling provided a coherent mechanistic framework linking chain-extension reactions to macroscopic viscoelastic reinforcement. These findings highlight the critical role of controlled reactive rheology in restoring melt integrity of rrPET and provide a fundamental basis for understanding the interplay of degradation, chain extension, and network formation in branched polyesters.