Water Absorption, Dimensional Stability, and Mold Susceptibility of Organically-modified-Montmorillonite Modified Wood Flour/Polypropylene Composites

Wood flour (WF) was modified by sodium-montmorillonite (Na-MMT) and didecyl dimethyl ammonium chloride (DDAC) in a two-step process to form organically-modified-montmorillonite (OMMT) inside the WF with varied MMT concentration (0.25, 0.5, 0.75, and 1%, respectively). Then, the modified WF was mixed with polypropylene (PP) to produce WF/PP composites. The WF and WF/PP composites were characterized, and the water absorption, dimensional stabilities, and the mold susceptibility of the composites against Aspergillus niger, Penicillam citrinum, and Trichoderma viride were investigated. The results showed that Na-MMT was successfully transformed to OMMT inside WF. Owing to the hydrophobic nature and barrier effect of OMMT on water permeability, the composites showed some improvements in water resistance, dimensional stabilities and antibiotic performance. MMT concentration was also an important factor. The water repellency and dimensional stability were improved with increasing MMT concentration at first and then dropped after the MMT concentration exceeded 0.5%. However, the mold resistance of the composites increased along with increasing MMT concentration. With 1% MMT treated, the mold growth rating decreased to 1 (mold covering of 0-25%). These results suggested that OMMT modified WF had a positive effect on restricting water absorption, swelling, and mold susceptibility for the WF/PP composites.