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

One of the drawbacks of phenol-formaldehyde (PF) resol resin is its slow cure which requires longer hot-pressing time for the manufacture of wood composite 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 resin for the manufacture of medium density fibreboard. The thermal behaviour of carbonate-modified PF resol resins was characterized with differential scanning calorimetry (d.s.c.) using three different thermal scanning methods (single-heating rate, multi-heating rate and isothermal method). The results of the single-heating rate method were not consistent when compared to the other two methods. The rate constants were calculated with the activation energy and pre-exponential factor obtained by the multi-heating method. The calculated rate constant increased with increasing carbonate level and the temperature selected. The isothermal method revealed that the curing of propylene carbonate-modified resins follows autocatalytic kinetics while the other two additives showed nth-order kinetics with a partial autocatalytic effect. (C) 1999 Elsevier Science Ltd. All rights reserved.