Role of Curing Kinetics in Tuning the Evolution of Density, Fluidity, and Microscopic Characteristics of Epoxy Resin

Evolutions in the structures and properties of epoxy resins in the curing process are crucial in determining their performance and processability. During this process, the kinetics of curing reactions plays a pivotal role in affecting the growth of polymer networks and the alteration of physical properties. This study investigates the influence of reaction kinetics on the curing of DGEBA-DDS epoxy resin using molecular dynamics, with a particular focus on the structure and property evolutions at low to medium curing degrees. By manipulating the reaction probability ratio of cross-linking to linear polymerization between 10 0 and 10 –4, we simulate the curing process under diverse reaction kinetics. The simulation results reveal that decreasing the probability ratio delays the formation of cross-linked polymers, substantially affecting the evolution of multiple properties. A lower probability of cross-linking reaction leads to faster shrinkage and a slower increase in viscosity, which may enhance the performance of the material by reducing internal stress buildup during curing when used as filling materials. This faster shrinkage and slower viscosity increase occur because oligomers with lower cross-linking, characterized by their lower fractal dimensions, encounter less resistance to diffusion compared to those with higher cross-linking. The quantitative statistical analysis in this study demonstrates that by adjusting the rates of linear and cross-linking reactions, the desired property evolution can be achieved, thereby optimizing the performance and functionality of epoxy-based materials for various applications.