How Durable Is Particleboard? Part II: Effect of Temperature and Humidity

Eight different Douglas-fir flakeboards of various densities and containing different types and amounts of binders were tested after exposure to four different laboratory controlled conditions. A repeating cyclic exposure of 1 week at 158?F. and 20 percent relative humidity followed by 1 week at 80?F. and 90 percent relative humidity for 2 years caused much more deterioration than continuous exposure did at either of the above conditions. It appears that the particleboard deterioration takes place because of the combined effects of springback from compression set, deterioration of the binder, and differential shrinkage of the adjacent particles during moisture content change. The phenolic resin-bonded boards were more durable than urea resin-bonded boards, apparently because the phenolic resin binder did not deteriorate in conditions of high temperature and high humidity as readily as did the urea resin binder that was used in this study. Wax did not improve the performance of the specimens that were bonded with 4 percent urea resin in these laboratory-controlled conditions probably because wax is not effective as a water vapor repellent. Increasing the resin content from 3 to 6 percent with phenolic resin and from 4 to 8 percent with urea resin definitely improved the performance of the specimens, apparently because the extra binder increased the resistance of the board to springback and differential shrinkage stresses.

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