Natural durability of organomodified layered silicate filled wood flour reinforced polypropylene nanocomposites

Abstract

AbstractThe effect of organomodified montmorillonite (OMMT) loading on the natural durability properties of polypropylene/wood flour composites exposed to brown-rot fungi (Coniophora puteana) was studied. To meet this objective, the blend composites were prepared through the melt mixing of polypropylene/wood flour at 50% weight ratios, with various amounts of OMMT (0, 3 and 6 per hundred compounds [phc]) in a hake internal mixer. The samples were then made by injection molding. The amount of coupling agent was fixed at 2 phc for all formulations. After specimen and culture medium preparation, the specimens were exposed to the purified fungus at 25°C and 75% relative humidity for 14 weeks. Identical specimens of the same composite, without being exposed to the fungus, were provided as the control specimens. After the discussed periods; weight loss, flexural strength, flexural modulus, hardness, water absorption, and thickness swelling of specimens were measured. Results indicated that OMMT had significant effects on the natural durability of the studied composite formulations. All mechanical properties were affected by the fungus, to a greater extent in the case of specimens without OMMT than the specimens with OMMT. Furthermore, the flexural strength and modulus increased with an increase of OMMT up to 3 phc and then decreased. However, the impact strength, water absorption and thickness swelling was decreased with increase of OMMT loading. Also, the lowest weight loss and the highest hardness were observed in the composite containing 6 phc organoclay. The morphology of the nanocomposites was examined by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Morphological findings revealed that intercalation came from the sample with 3 phc concentration of OMMT, which implies the formation of intercalation morphology and better dispersion than 6 phc.