Effect of Density and Polymer Content on the Hygroscopic Thickness Swelling Rate of Compression Molded Wood Fiber/Polymer Composites
Keywords:
Swelling rate, compression molding, thickness swelling, wood fiberboard, wood fiber/polymer compositesAbstract
The effects of polymer content and board density on the hygroscopic thickness swelling rate of compression-molded wood fiber/polymer composites were investigated in this study. A swelling model developed by Shi and Gardner (2005) was used to study the thickness swelling process of wood fiber/polymer composites exposed to water vapor conditions in which a parameter, KSR, was used for the comparison of the swelling rates. The polymer materials used to process the wood fiber/polymer composites were from a reclaimed automobile plastic mixture, also called polymer fluff. Polymeric diphenylmethane diisocyanate (pMDI) resin was used as a binder. Six polymer contents (0, 15, 30, 45, 60, and 100%) and four target specific gravities (0.55, 0.75, 0.90, and 1.00) were evaluated in the experiments using the swelling model. It was shown that the swelling model successfully fit the empirical swelling rate data as impacted by different board densities and polymer contents. Board density has a significant effect on the swelling rate of the composites. The swelling rate increased linearly as board density decreased. The effect of polymer content on the swelling rate depends partially on board density. Polymer content did not show a significant effect on swelling rate at an oven-dry density of 900 kg/m3. It was also confirmed from this study that the accuracy of the swelling model prediction is a function of the magnitude of the swelling rate parameter. The lower the thickness swelling rate of the composites, the more accurate the prediction obtained from the swelling model.References
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