Differential scanning calorimetry of phenol-formaldehyde resins cure-accelerated by carbonates

One of the drawbacks of phenol-formaldehyde (PF) resol resin is its slow cu re which requires longer hot-pressing time for the manufacture of wood comp osite products, especially for thick fibreboard products. In this study, PF resol resin was modified with three carbonates (i.e. propylene carbonate, sodium carbonate and potassium carbonate) to accelerate the cure of the res in for the manufacture of medium density fibreboard. The thermal behaviour of carbonate-modified PF resol resins was characterized with differential s canning calorimetry (d.s.c.) using three different thermal scanning methods (single-heating rate, multi-heating rate and isothermal method). The resul ts of the single-heating rate method were not consistent when compared to t he other two methods. The rate constants were calculated with the activatio n energy and pre-exponential factor obtained by the multi-heating method. T he calculated rate constant increased with increasing carbonate level and t he temperature selected. The isothermal method revealed that the curing of propylene carbonate-modified resins follows autocatalytic kinetics while th e other two additives showed nth-order kinetics with a partial autocatalyti c effect. (C) 1999 Elsevier Science Ltd. All rights reserved.