DSC characterisation of urea‐formaldehyde (UF) resin curing

Purpose The purpose of this paper is to investigate the effects of various catalyst contents, resin solid contents, catalyst species and wood extract on urea‐formaldehyde (UF) curing by differential scanning calorimetry (DSC) technique. The finding obtained would benefit the manufacturers of UF‐bonded composite panels. Design/methodology/approach The UF curing rate under each condition in terms of DSC peak temperature was measured by high‐pressure DSC at a heating rate of 15°C/min; the correlations of peak temperature with catalyst content, resin solid content, catalyst species and wood extract, respectively, were regressed via a model equation, which described the curing characteristics of the UF bonding system. Findings A model equation, T p = A · EXP(− B · CC per cent)+ D , was proposed to characterise the DSC peak temperatures or the rate of UF curing with regressing coefficients greater than 0.97 (commonly greater than 0.99). The constants A and B in the model equation were found to correspond to kinetic characteristics of UF resin curing reaction. The constant D in the model equation is believed to be associated with the utmost peak temperature, which implies that the DSC peak temperature will finally reach a maximum with catalyst content increasing. It was also found that the wood extracts having higher pH value and base buffer capacity had stronger catalyses on UF curing. Research limitations/implications The catalysts commonly used in medium density fibreboard plants or particleboard plants are those having the utmost peak temperature of about 90‐95°C; the catalyses of wood extracts were much weaker than that of catalyst NH 4 Cl. Practical implications The model equation could be used to predict the peak temperature or the curing rate of UF resin, and to quantify the effects of wood extracts on UF curing. Originality/value The study developed a model equation that can well characterise the UF curing, and quantified the effects of wood extracts on UF curing.