Extension of Isoconversional Analysis to Diffusion‐Controlled Epoxy Cure Kinetics: Comparison With Model‐Fitting Approaches

ABSTRACT The curing kinetics of epoxy resins is commonly described using either model‐fitting or model‐free (isoconversional) approaches. Among model‐fitting methods, the Kamal–Sourour model is widely accepted, but it requires an adjustment to describe the transition to diffusion‐controlled regimes at high conversion. Isoconversional methods, while more flexible, have been traditionally regarded as unable to capture the curing evolution under diffusion control. In this work, we present an extension of isoconversional analysis to diffusion‐controlled regimes and a parallel modification of the Kamal–Sourour model incorporating a diffusion term for consistent comparison. We first demonstrate that isoconversional methods can reproduce all the phenomenology derived from the Kamal–Sourour model. Both approaches are then applied to experimental curing data of the commercial RTM6 epoxy‐based resin, showing that isoconversional analysis provides superior ability to capture the complex experimental phenomenology. Furthermore, the proposed extension of isoconversional analysis yields accurate predictions even when diffusion governs the curing rate. The results demonstrate that isoconversional methods, once extended to account for diffusion control, outperform model‐fitting approaches in reproducing the experimental curing phenomenology. Reliable kinetic models are essential for optimizing cure cycles in industrial manufacturing processes; the proposed methodology provides an accurate and flexible framework to develop such models for epoxy‐based composite structures.