Cyclic Moisture Conditions and Their Effect on Strength and Stability of Structural Flakeboards

Durability of phenol-bonded particleboards under accelerated aging conditions has been a matter of concern for many years. This exploratory study outlines a series of cyclic accelerated exposures on laboratory-prepared flakeboards and the effects of the exposure cycles on dimensional movement and strength retention. Exposures included the ASTM D-1037 test, vacuum-pressure-soak and OD cycles, and high-low RH cycles. Generally, specimens which performed well in one exposure also performed well in others, but several new relationships were found. In particular, specimens responded differently in some ways to wet-dry cycles as compared to high-low humidity cycles. For instance, high-low humidity does not produce the longitudinal shrinkage associated with wet-dry cyclic conditions. Also, specimens which fared poorly in strength retention after wet-dry cycles often performed in an improved fashion following high-low humidity cycles. Thus, a wet-dry cyclic test may not be best for judging durability of products not intended for wet-dry cyclic exposures.

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