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<p>Cold-curing epoxy adhesives, due to their rapid curing at room temperature and high bonding strength, are widely used in the external bonding reinforcement and near-surface mounting technologies of fiber-reinforced composite materials and concrete. However, the performance of these cold-curing epoxy adhesives exhibits higher susceptibility to the effects of varying gradient temperatures compared to heat-cured structural adhesive systems. This study systematically evaluated the temperature threshold effects on two cold-curing epoxy structural adhesive formulations through comprehensive mechanical property analyses across various tested and curing temperature ranges. The experimental results demonstrated that test temperatures exceeding the heat distortion temperature (HDT) induced significant molecular chain mobility, leading to material softening. Specifically, the standard-temperature tensile and shear strengths decreased by 38% and 32%, respectively, compared to those at 60&#xa0;°C. In the low-temperature range of − 5&#xa0;°C to 5&#xa0;°C, while tensile strength increased by 23%, the interfacial brittleness reduced the elongation at break, resulting in only a 2% increase in shear strength and an overall degradation of performance. The curing temperature exhibited nonlinear effects on performance: below HDT, increasing temperature enhanced crosslinking density and improved mechanical properties; above HDT, pre-curing thermal stress caused molecular structure damage, thereby degrading performance. Notably, shear performance was found to correlate more closely with material toughness rather than solely with the degree of cure.</p>

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Temperature-dependent mechanical behavior and threshold effects of heat deflection in cold-cured epoxy structural adhesives

  • 期刊论文

  • 发表日期：

    2025年11月20日

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  • Kunpeng Lu,
  • Xuexue Xue,
  • Xiaoyuan Pei,
  • Shigang Luo,
  • Wen Xu,
  • Peiwen Yang,
  • Zhiwei Xu

摘要

Cold-curing epoxy adhesives, due to their rapid curing at room temperature and high bonding strength, are widely used in the external bonding reinforcement and near-surface mounting technologies of fiber-reinforced composite materials and concrete. However, the performance of these cold-curing epoxy adhesives exhibits higher susceptibility to the effects of varying gradient temperatures compared to heat-cured structural adhesive systems. This study systematically evaluated the temperature threshold effects on two cold-curing epoxy structural adhesive formulations through comprehensive mechanical property analyses across various tested and curing temperature ranges. The experimental results demonstrated that test temperatures exceeding the heat distortion temperature (HDT) induced significant molecular chain mobility, leading to material softening. Specifically, the standard-temperature tensile and shear strengths decreased by 38% and 32%, respectively, compared to those at 60 °C. In the low-temperature range of − 5 °C to 5 °C, while tensile strength increased by 23%, the interfacial brittleness reduced the elongation at break, resulting in only a 2% increase in shear strength and an overall degradation of performance. The curing temperature exhibited nonlinear effects on performance: below HDT, increasing temperature enhanced crosslinking density and improved mechanical properties; above HDT, pre-curing thermal stress caused molecular structure damage, thereby degrading performance. Notably, shear performance was found to correlate more closely with material toughness rather than solely with the degree of cure.