To evaluate the effect of fungal decay on the physico-mechanical properties of natural composites, a commercial extruded bagasse/polypropylene composite from a manufacturer was sampled. Weight loss, long-term water absorption, flexural modulus, flexural strength, and unnotched impact strength were determined after incubation with white and brown rot fungi for 14 weeks. Results indicated higher water absorption for all incubated samples. However, the water absorption capacity of brown-rotted samples was significantly higher than that of white rotted ones. The brown rot fungus caused more weight loss than the white rot fungus. Modulus of rupture and modulus of elasticity declined after incubation with fungi. The brown rot fungus generally caused a greater reduction in flexural strength than did the white rot fungus. Fungal decay had no significant influence on unnotched impact strength.

Mechanical, morphological, and thermal properties of injection molded, chemimechanical pulp (CMP)-reinforced polypropylene (PP) composites were investigated as a function of different concentrations of maleic anhydride-grafted PP. It was found that tensile strength and failure strain and the notched impact strength increased progressively with increasing compatibilizer content, whereas the addition of any concentration of compatibilizer did not alter the tensile modulus. Scanning electron microscopy — micrographs of tensile fracture surfaces of composites with 2% compatibilizer indicated very little fiber pullout and many fractured fibers. The thermal stability of pure PP was found to be higher than that of CMP-reinforced PP composites. With addition of compatibilizer, the thermal stability of the composites was slightly increased. The activation energy was determined to describe the energy consumption of the initiation of the thermal degradation process. The activation energy of the composites was found to depend on the dispersion and interfacial adhesion of CMP and PP matrix.

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The effect of MAPE as compatibilizer on mechanical and morphological properties of a wheat straw/high density polyethylene composite was investigated. Tensile strength, tensile modulus, tensile energy absorption, failure strain, and notched Izod toughness were much higher for composites with compatibilizer as compared with the composites with no compatibilizer. The use of 2% compatibilizer improved the tensile strength as high as 43%, tensile modulus to 116% and impact strength (notched) by 12%. Remarkably improvements were attained even with 1% compatibilizer. There was little difference in the properties obtained between the 1% and 2% compatibilizer. SEM micrographs of tensile fracture surfaces with 2% compatibilizer indicated a continuous failure and the particles are not released from the matrix which is the case in samples without compatibilizer.

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As the major component of WPCs, wood flour species plays an important role on the properties of the resulting composites. The effect of wood species as filler and reinforcement and MAPE as compatibilizer on mechanical properties of wood flour/high-density polyethylene composite was investigated. The wood species used in this study were loblolly pine and hybrid Euro-American poplar. The mechanical properties such as tensile properties and notched impact toughness were tested. Poplar flour provides an improvement in tensile strength, tensile modulus, tensile energy absorption, and failure strain over pine. Tensile strength of both the composites was much higher for compatibilized composites as compared with uncompatibilized ones. For the pine composites, tensile modulus improvements were attained even with 1% compatibilizer. There was little difference in the properties obtained between the 1% and 2% compatibilizer. For the poplar composites, adding 1% compatibilizer did not have significant effect on tensile modulus and there was a significant drop in tensile modulus with further 2% increase in the compatibilizer. Wood species and compatibilizer percent did not have significant effect on the notched Izod toughness.

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