Study on the Impact of Diluent Dosages on the Epoxy-Polythiol Self-Healing System

Self-healing technology is an effective method for enhancing the crack resistance of cement-based composites. This study focuses on the impact of the environmentally friendly diluent C12-14 alkyl glycidyl ether (AGE) on the performance of the epoxy resin-polythiol (rimethylolpropane tris (3-mercaptopropionate), TMPMP) self-healing system, examining core fluidity, microcapsule properties, molecular dynamics, and the mechanical properties of cured products. The results show that as the AGE dosage increases, the particle size distribution of microcapsules becomes more concentrated, and the dispersion of particles is improved. Fourier-transform infrared spectroscopy confirms the successful encapsulation of E-51 and AGE. Microcapsules maintain structural integrity at high temperatures of 423.15 K. The onset thermal degradation temperature of the mixture shows an increasing trend with reduced AGE dosage. Specifically, TMPMP_35% exhibits an onset degradation temperature of 370.95 K, while that of TMPMP_20% is increased by 57.57% compared to TMPMP_35%. Conversely, the initial and peak temperatures of the curing reaction decrease with less AGE incorporation. Thermodynamic analysis reveals that activation energy (E) initially increases and then decreases with increasing AGE. The frequency factor (A) correlates positively with the heating rate, indicating that the curing reaction's reactivity is closely linked to heating rate. Minor variations in the reaction rate constant (k) indicate that the self-healing system maintains stable reactive activity at low temperatures. Notably, the AGE dosage significantly affects the rigidity of the self-healing system; the average Young's modulus inversely correlates with AGE dosage, with the most substantial decrease of 5.88% occurring when AGE increases from 30% to 35%. This study offers insights into optimizing diluent ratios to balance self-healing and mechanical properties, essential for developing high-performance self-healing cement materials.