Deterioration of wood-based boards subjected to outdoor exposure in Tsukuba
Various types of wood-based boards were analyzed for deterioration after being exposed to an outdoor environment for 5 years in Tsukuba, Japan. In phenol–formaldehyde resin bonded particleboard (PB(PF)) and aspen oriented strand board (OSB(aspen)), longer exposure caused a greater reduction in the modulus of rupture and internal bond strength, an increase in the coefficients of variation, and a decrease in 95 % lower tolerance limit at the 75 % confidence level (95TL). Nail-head pull-through and lateral nail resistance were also reduced by outdoor exposure, but their coefficients of variation and 95TL were not significantly affected. In contrast, methylene diphenyl diisocyanate bonded medium density fiberboard (MDF(MDI)) only showed a slight deterioration of these properties even after 5-year exposure, and the coefficients of variation and 95TL hardly changed. After 5-year exposure, the retention of shear load in one-plane at relative displacement of 1.0 mm was high in MDF(MDI) and OSB(aspen) at 93.5 and 78.5 %, respectively, but low in PB(PF) at 41.1 %. As with PB(PF), OSB(aspen) also showed a sharp decrease in the modulus of rupture and internal bond strength, but only slightly reduced shear load in one-plane.
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.
Magnetic properties of Lu2Fe17 crystals
Abstract We present the results of crystal structure and magnetization studies of three single crystals grown from melts of different nominal compositions in the vicinity of the Lu2Fe17 stoichiometry. The ferromagnetic state of the crystals is strongly dependent on the real sample composition and the local atomic ordering. A drastic difference is observed in the behaviour of the ferro–antiferromagnetic transition, even in crystals for which almost identical composition and crystal parameters were determined by microprobe and X-ray analysis.