Thermal cure kinetics of cold-setting melamine–urea–formaldehyde resins with high melamine content

Even though cure kinetics of melamine–urea–formaldehyde (MUF) resins with low melamine contents (0–20 mass%) and high-temperature curing have been studied, research on the thermal cure kinetics of cold-setting MUF resins with relatively high melamine content (20–40 mass%) is limited. Therefore, this study reports thermal cure kinetics of cold-setting MUF resins synthesized with three melamine contents, using differential scanning calorimetry. A model-fitting method (Kissinger), three model-free kinetic methods (Friedman (FR), Flynn–Wall–Ozawa (FWO), and Kissinger–Akahira–Sunose (KAS)), and a nonlinear isoconversional (or Vyazovkin) method were employed to theoretically estimate the cure kinetics of cold-setting MUF resins with high melamine content. The results of Kissinger analysis provided reliable activation energy (E _a) which was also comparable with those of isoconversional analysis. As the degree of conversion (α) increased, the activation energy (E _α) of MUF resins decreased, regardless of melamine content. However, the activation energy (E _a), isoconversional activation energy (E_α), and the peak temperature (T _p) increased as the melamine content increased. Two methods such as KAS and Vyazovkin methods were reliable in estimating their cure kinetics based on R ² values and cure kinetic parameters. Analysis of the cure kinetics showed that all melamine contents MUF resins followed an nth-order reaction (OR (n > 1)) model.