Accelerated aging and outdoor weathering of aspen waferboard

This study was initiated in 1983 to evaluate the durability of waferboard in accelerated-aging and outdoor-weathering environments. Small-size specimens of two types of commercial aspen waferboards were subjected to four accelerated-aging tests (ASTM 6-cycle, CSA 2-hr. boil, AFNOR V 313, APA 6-cycle) and to outdoor weathering for 1, 2, 3, and 5 years at Canadian prairie, central, and maritime locations. Quarter-panel specimens were also exposed to outdoor weathering. Degradation was assessed on the basis of changes in thickness swelling (TS), modulus of rupture (MOR), apparent modulus of elasticity (MOE), internal bond strength (IB), surface hardness (SH), nail withdrawal resistance (NWR), and lateral nail resistance (LNR). Among the accelerated-aging tests, in general, the AFNOR and the APA tests were generally the least severe and the CSA test the most severe. The maritime location, with the wetter environment, was the most severe among the outdoor weathering sites. Accelerated aging was significantly more severe than outdoor weathering in regard to TS. Long-term outdoor weathering effects on bending properties were simulated best by the ASTM and the CSA test procedures. Large-specimen tests were characterized by slightly higher residual bending properties, lower MOR and higher MOE, and lower variability in test results. Weathering for 1 year caused thickness to increase and bending properties to decrease significantly. The long-term effects were significantly more severe in comparison to the initial exposure period for aU properties, with the exception of TS. MOR of weathered structural-size waferboard specimens was reduced by as much as 39 percent and MOE by 52 percent and nail holding properties by 60 percent. If waferboard is to be subjected to the elements for extended periods, its weathering properties must be improved.