Estimating maximum water absorption of wood fiber/polymer fluff composites

The objective of this study was to develop a model to estimate the maximum water absorption (MWA) of wood fiber/polymer Ruff composites as a function of polymer fluff content and board density. Polymeric diphenylmethane diiso cyanate (PMDI) resin bonded dry-process wood fiber/polymer fluff composites were used in this study. Six polymer fluff contents (0, 15, 30, 45, 60, an d 100%) and four target oven-dry board densities in the range of 0.50-1.00 g/cm(3) were studied. A water immersion test was conducted on these boards. The effect of irreversible thickness swelling after water immersion (TSi) on the estimation of the maximum water absorption was evaluated. It was sho wn that the irreversible thickness swelling had a quadratic relationship wi th polymer fluff content and a linear relationship with oven-dry board dens ity. The TSi of the composites used in this study was in the range of only 0.04-4.20%, which was negligible in the estimation of maximum water absorpt ion. The prediction of maximum water absorption from the MWA model develope d in this study was over 95% accuracy for most of the specimens. The maximu m water absorption had a linear relationship with the polymer fluff content and a reciprocal relationship with board density.