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<p>Poly(lactic acid) (PLA) is a sustainable alternative to conventional polymers; however, its brittleness and limited thermal resistance still restrict its use in more demanding applications. In this context, this study aims to systematically investigate the combined effect of plasticization with epoxidized soybean oil (ESO) and thermal annealing on the structure–property relationships of PLA, with the hypothesis that the synergistic action of these two strategies can simultaneously improve ductility and thermal performance without compromising material integrity. In this study, PLA was plasticized with epoxidized soybean oil (ESO), at concentrations of 2.5, 5, and 7.5 parts per hundred resin (phr), combined with a thermal annealing treatment. The blends were processed by extrusion and injection molding and were characterized before and after annealing (90&#xa0;°C for 5&#xa0;h) by means of chemical, thermal, mechanical, thermomechanical, and morphological analyses, in addition to evaluating ESO migration. The results demonstrated strong interaction between PLA and ESO, as evidenced by the low oil migration, the disappearance of the characteristic epoxy group band in Fourier Transform Infrared Spectroscopy (FTIR), and the predominantly single-phase morphology observed by Scanning Electron Microscopy (SEM). Annealing promoted a significant increase in crystallinity, with suppression of cold crystallization in the DSC (Differential Scanning Calorimetry) curves and a degree of crystallinity exceeding 55%. This improved molecular reorganization was directly reflected in the mechanical and thermomechanical performance, with a transition from brittle to ductile fracture, increased tensile strength, an increase of more than 10&#xa0;°C in the heat deflection temperature (HDT), and up to a 3.8-fold improvement in impact strength for the composition containing 7.5 phr of ESO. Therefore, the synergy between plasticization and annealing proved to be an effective, simple, and scalable strategy to enhance PLA performance, contributing to the development of sustainable materials with advanced properties.</p> Graphical abstract <p></p>

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From brittleness to toughness: tailoring PLA performance through epoxidized soybean oil in combination with controlled annealing

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月7日

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  • Clara Maria Marinho Serafim,
  • João Vitor Souto de Araújo Queiroz,
  • Carlos Bruno Barreto Luna,
  • Eduardo da Silva Barbosa Ferreira,
  • Emanuel Pereira do Nascimento,
  • Valmar da Silva Severiano Sobrinho,
  • Renate Maria Ramos Wellen,
  • Edcleide Maria Araújo

摘要

Poly(lactic acid) (PLA) is a sustainable alternative to conventional polymers; however, its brittleness and limited thermal resistance still restrict its use in more demanding applications. In this context, this study aims to systematically investigate the combined effect of plasticization with epoxidized soybean oil (ESO) and thermal annealing on the structure–property relationships of PLA, with the hypothesis that the synergistic action of these two strategies can simultaneously improve ductility and thermal performance without compromising material integrity. In this study, PLA was plasticized with epoxidized soybean oil (ESO), at concentrations of 2.5, 5, and 7.5 parts per hundred resin (phr), combined with a thermal annealing treatment. The blends were processed by extrusion and injection molding and were characterized before and after annealing (90 °C for 5 h) by means of chemical, thermal, mechanical, thermomechanical, and morphological analyses, in addition to evaluating ESO migration. The results demonstrated strong interaction between PLA and ESO, as evidenced by the low oil migration, the disappearance of the characteristic epoxy group band in Fourier Transform Infrared Spectroscopy (FTIR), and the predominantly single-phase morphology observed by Scanning Electron Microscopy (SEM). Annealing promoted a significant increase in crystallinity, with suppression of cold crystallization in the DSC (Differential Scanning Calorimetry) curves and a degree of crystallinity exceeding 55%. This improved molecular reorganization was directly reflected in the mechanical and thermomechanical performance, with a transition from brittle to ductile fracture, increased tensile strength, an increase of more than 10 °C in the heat deflection temperature (HDT), and up to a 3.8-fold improvement in impact strength for the composition containing 7.5 phr of ESO. Therefore, the synergy between plasticization and annealing proved to be an effective, simple, and scalable strategy to enhance PLA performance, contributing to the development of sustainable materials with advanced properties.

Graphical abstract