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<p>Epoxy resins are widely used in coatings, adhesives and composites due to outstanding adhesion and mechanical strength, yet high crosslinking density leads to inherent brittleness and low impact resistance, limiting their engineering application. To solve this problem, three diacid-based glycidyl ester toughening agents (GAEP, PAEP, AAEP) with gradient molecular chain lengths were synthesized to regulate the structure–property relationship and optimize the performance of E51 epoxy resin. Their chemical structures were verified by FTIR and ¹H NMR, with epoxy values of 0.493, 0.713 and 0.413&#xa0;mol/100&#xa0;g. The modifiers reduced system viscosity to 1672, 757 and 916 mPa·s and provided a controllable curing window of 69–73&#xa0;°C, improving processability. AAEP/E51 at 25:100 achieved prominent improvements in elongation at break (21.38%) and impact strength (13.4&#xa0;kJ/m²), while PAEP/E51 at 15:100 obtained a maximum shear strength of 30.94&#xa0;MPa for Kevlar fibers/PVDF bonding. SEM confirmed ductile fracture and improved fiber wettability. This work proposes a novel chain-length regulation strategy for epoxy toughening, providing a valuable reference for formula design and industrial application of modified epoxy systems.</p>

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Synthesis of diacid-derived toughening agents with variable chain lengths: structure design, toughening mechanism and property enhancement of E51 epoxy resin

  • 期刊论文

  • 发表日期：

    2026年5月23日

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  • Yang Yu,
  • Xiang Meng,
  • Xiaofeng Liu,
  • Xiaofeng He,
  • Qi Yue,
  • Zhanzhou Liu,
  • Tiejun Ge

摘要

Epoxy resins are widely used in coatings, adhesives and composites due to outstanding adhesion and mechanical strength, yet high crosslinking density leads to inherent brittleness and low impact resistance, limiting their engineering application. To solve this problem, three diacid-based glycidyl ester toughening agents (GAEP, PAEP, AAEP) with gradient molecular chain lengths were synthesized to regulate the structure–property relationship and optimize the performance of E51 epoxy resin. Their chemical structures were verified by FTIR and ¹H NMR, with epoxy values of 0.493, 0.713 and 0.413 mol/100 g. The modifiers reduced system viscosity to 1672, 757 and 916 mPa·s and provided a controllable curing window of 69–73 °C, improving processability. AAEP/E51 at 25:100 achieved prominent improvements in elongation at break (21.38%) and impact strength (13.4 kJ/m²), while PAEP/E51 at 15:100 obtained a maximum shear strength of 30.94 MPa for Kevlar fibers/PVDF bonding. SEM confirmed ductile fracture and improved fiber wettability. This work proposes a novel chain-length regulation strategy for epoxy toughening, providing a valuable reference for formula design and industrial application of modified epoxy systems.