| The purpose of this study was to understand the mechanisms and effects of moisture uptake on wood-plastic composites. Fick's law was applied to estimate the diffusion rate constants. The dynamics of absorption were studied with respect to polarity, void volume, temperature, and chemical treatment. Four types of fibers: kenaf, hardwood, softwood, and copper chrome arsenate treated softwood were characterized by inverse gas chromatography with acid-base concept. Softwood, kenaf, and hardwood fibers imparted varying permeability to composites indicating that void volume and polarity play roles in diffusion. CCA treatment reduced polarity and diffusion coefficient. High molding pressure reduced the permeability coefficient, probably through reduction in void volume. Composites (50–50) took up 20% moisture resulting in strength, stiffness, and fracture energy losses. CCA treated wood-fiber plastic out-performed untreated fibers-plastic under moisture. A leaching test showed that the preservative leached more slowly from the treated fiber-composite than from the fiber alone. |
