Hygroscopic thickness swelling rate of wood polymer nanocomposite

In this study, the effects of nanoclay and coupling agent content on the clay dispersion and thickness swelling behavior of PP/WF composites were investigated. To meet this objective, the blend nanocomposites were prepared by melt mixing PP and beech WF at 50% weight ratios, with various amounts of nanoclay (0, 3, and 6 phc) and MAPP (0, 2, and 4 phc) in Hakee internal mixer. The samples were then made by injection molding. The thickness swelling rate of the composites was evaluated by immersing them in water at room temperature for several weeks (up to 3000 h). A swelling model developed by Shi and Gardner (2006) was used to study the thickness swelling process of composites, from which the parameter, K-SR, can be used to quantify the swelling rate. The results indicated that equilibrium thickness swelling and also shorter equilibrium time (the time to reach the equilibrium thickness swelling) decreased with increase of clay loading, and also the effect of compatibilizer was positive in terms of enhancing the dimensional stability of the composites. The swelling model developed was a good predictor of the hygroscopic swelling process of wood plastic composites. The composites containing PP had a higher K-SR than those containing MAPP or nanoclay. The minimum K-SR values were observed in composites made of 3 phc of nanoclay and 4 phc of MAPP. The micrographs of XRD and TEM confirmed the intercalation morphology in nanocomposite samples.