Surface Roughness of Wood-Based Panels After Aging

The surface roughness of painted and unpainted wood-based panels has been measured with a fine, 3-pm stylus over a panel length of 5 cm. In this way both micro- and macrostructure are evaluated. The surface profile, the depth of surface profile, and the arithmetic mean deviation have been determined. Such a test is a useful tool in evaluating the effect of aging. Great differences in surface roughness have been observed on panels subjected to different methods of accelerated aging. The increase in surface roughness after some methods for accelerated aging is greater than the corresponding decrease in strength and depends mainly on how water penetrates into the panels during aging. Among different types of unpainted panels there are significant differences in surface stability on accelerated aging. Fiber building boards exhibit much larger surface stability than particleboards do, independent of the type of resin used. Panels of solid wood show only minor surface changes, while in those of plywood the initial microcracks become markedly deepened. Natural weathering during 4 years’ exposure at an angle of 45? facing south seems to degrade the surface less than the accelerated methods. On the other hand, other defects were observed after natural weathering. The methods for accelerated aging are therefore not suitable for evaluating the surface properties of wood-based panels since they are too drastic. They are more suitable for production control of specific panels.

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