Long-term Water Absorption Behaviour of Polypropylene/Wood Flour/Organoclay Hybrid Nanocomposite.

Recently, to improve the properties of wood plastic composite (WPC), incorporation of nanofiller has been considered. In this study, hybrid composite of polypropylene/wood flour/nanoclay with different concentrations of nanoclay and maleated polypropylene (MAPP) as compatibilizer were fabricated in an internal mixer. The long-term water absorption of the composites was evaluated by their immersion in water at room temperature for several weeks (up to 3000 h). Water diffusion coefficients were evaluated. The results indicate that water absorption decreases with increase in clay loading. The morphology of nanoclay was determined by X-ray diffraction (XRD) and transmission electron microscope and the effect of morphology on water absorption is discussed. Due to inadequate compatibilizer, exfoliated morphology of nanoclay is not obtained but the intercalation has occurred. The order of intercalation for samples containing 3 phc is higher than that of 6 phc at the same MAPP content due to some agglomerations of organoclay. The effect of compatibilizer has been positive in terms of enhancing the dimensional stability of the composites and mechanical properties. The maximum elastic modulus may be related to 3 phc of nanoclay and 4 phc of MAPP. The maximum water absorption and diffusion coefficients are decreased by increasing the clay and MAPP contents. The mechanism of water absorption of the composites under study followed the kinetics of a Fickian diffusion process.