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.
Predicting internal bond strength of particleboard under outdoor exposure based on climate data: comparison of multiple linear regression and artificial neural network
The internal bond strength (IB) of a commercial particleboard put under various outdoor exposure conditions were modeled using a multiple linear regression (MLR) and an artificial neural network (ANN). The outdoor exposure data used in this study were collected from the results of past outdoor exposure tests conducted at eight locations across Japan from 2004 to 2011. The data from five locations were used to develop the MLR model and the ANN model for predicting the IB of particleboard under outdoor exposure based on climate data including exposure duration, annual mean temperature, annual sunshine duration, and annual precipitation. The performance of the models was assessed by comparing predicted IB values with measured ones for the remaining three locations. The MLR model gave a high R2 of 0.87 and a low root mean square error (RMSE) of 0.07 MPa, while the ANN model gave an R2 of 0.93 and an RMSE of 0.05 MPa. Thus, both models were demonstrated to be applicable to particleboards exposed at different locations in Japan. A statistical test of the MLR model revealed that the IB was influenced negatively by exposure duration, temperature, and precipitation. These influences were confirmed by the sensitivity analysis of the ANN model, and the analysis also showed an additional positive influence of sunshine duration on IB.
Ignition and burning rates of segregated waste combustion in packed beds.
Recent developments in national recycling and re-use programmes for municipal waste have led to segregation of an increasing proportion of waste to enhance material recovery. Several of the segregated streams contain materials that can not viably be re-used or recycled but can be used for energy recovery. In this study, the combustion of cardboard and waste wood was investigated in a small-scale packed bed reactor in order to provide fundamental data for the design/operation of moving bed furnaces. Key parameters of combustion including the ignition and burning rates were evaluated for various air flowrates and compared to the modelling results. Two successive stages of combustion were identified for both samples: the propagation of ignition front into the bed and combustion of the fuel above the ignition front. The burning rate of cardboard reached a peak of about 300 kg/m(2)h at the air flowrate of 936 kg/m(2)h and decreased at higher air flowrates. For waste wood, both the ignition and burning rates increased in the tested range of the air flowrate up to 702 kg/m(2)h, of which the values were very close to those for the cardboard. The model prediction was in good agreement with the test results for waste wood. However, the burning rate for cardboard was under-predicted due to strongly irregular shapes of the fuel.