Cure kinetics of aqueous phenol-formaldehyde resins used for oriented strandboard manufacturing: Effect of wood flour

The effect of wood flour on the cure kinetics of commercial phenol-formaldehyde resins used as oriented strandboard face and core adhesives was studied using differential scanning calorimetry. The wood flour did not change the cure mechanism of the face resin, but lowered its cure temperature and activation energy and increased its cure reaction order. For the core resin (CR), the wood flour lowered the onset cure temperature, and caused separation of the addition and condensation reactions involved in curing of CR. Compared with neat CR, the addition reaction of CR/wood mixture also followed an nth-order reaction mechanism but with a lower reaction order, while the condensation was changed from an autocatalytic reaction to an nth-order one. The addition reaction happened at temperatures lower than 90 degrees C, and the condensation reaction was dominant at temperatures higher than 110 degrees C. The proposed models fitted the experimental data well. Relationships among cure reaction conversion (cure degree), cure temperature, and cure time were predicted. (c) 2006 Wiley Periodicals, Inc.