Comparison between climatic factors and climate deterioration index on strength reduction of particleboards subjected to various climatic conditions in Japan

An outdoor test on particleboards subjected to various climatic conditions was conducted in Japan. The significant climatic factors that reduce the particleboard strength (bending strength and internal bond strength) were investigated using multiple regression analysis. The climatic factors that reduce strength were temperature, sunshine duration, and/or precipitation. These three factors were not always significant; the significant climatic factors were different for each exposure time. In addition, the effects of climatic factors on strength reduction were different. Thus, multiple regression analysis using each climatic factor separately was not powerful. Therefore, the three climatic factors were combined into a first principal component using principal component analysis. The principal component score is referred to as the climate deterioration index (CDI). Strength at each exposure time decreased linearly with increasing CDI. The CDI is simpler and more useful as a climate index than individual climatic factors for predicting the strength reduction. In addition, both the relationship between CDI and strength reduction at each exposure time using analysis of covariance and the effects of CDI and exposure time were significant.