Construction of epoxy composites with double alternating “rigid-flexible” structures: Curing kinetics and thermal/mechanical properties

Abstract

The curing rate, post-curing modulus, and strength of epoxy resin are key performance indicators for epoxy resin-based composites. Optimizing these factors is essential for improving production processes and expanding practical applications. Functionalized rigid-flexible bilayer transition interfaces between nano-ZnO and epoxy resins were developed using chitosan (CS) and 1,2,3-Tris(glycidyloxy)propane (GTE). Their impact on the curing characteristics, rheology, and mechanical properties of the composites was investigated. The activation energies of pure EP and systems containing ZnO, ZnO-CS, and ZnO-CS-GTE were studied using non-isothermal calorimetry, obtaining 53.604 KJ/mol, 52.548 KJ/mol, 56.66 KJ/mol, and 51.482 KJ/mol, respectively. ZnO-CS-GTE showed a notably stronger promotional effect. Nano-ZnO inhibited gelation due to filler aggregation at 80 °C for 4 min, while ZnO-CS-GTE promoted gelation in just 2.6 min owing to its functional groups, achieving a modulus near 1 GPa after curing. Mechanical studies revealed that the tensile, flexural, and compressive strengths of the ZnO-CS-GTE system increased by 48.52 %, 32.67 %, and 45.01 %, respectively, with flexural and compressive moduli rising by 15.14 % and 15.76 %. The rigid-flexible interface enhanced the dispersion of epoxy resin and strengthened interfacial adhesion.