Modified method for evaluating weathering intensity using outdoor exposure tests on wood-based panels

The deterioration of wood-based panels at eight sites in Japan over 7?years of outdoor exposure was investigated. In particular, the modulus of rupture (MOR) retention and internal bond strength (IB) retention after 7?years of exposure were compared among panels and sites. The deterioration of panels was greater in southern Japan than in northern Japan. The strength retentions in northern Japan decrease linearly, while those in southern Japan decreased exponentially. To quantify regional differences, deterioration rates were calculated based on three different weather conditions (precipitation, temperature, and sunlight hours), and the significance of each of these parameters on panel deterioration was determined. We found that the correlation coefficients between both IB and MOR retention and weathering intensity were the same whether we used 10-day, monthly, or daily weathering data.