Omar Faruk

Physico-mechanical studies of wood fiber reinforced composites

Wood polypropylene composites (WPC) of different compositions (30, 40, and 50%) have been prepared using maleic anhydride–polypropylene copolymer of different percentage (5 and 10% relative to their wood fiber content). Tensile, flexural, fracture toughness, and impact test of the prepared WPC were carried out. From the results, it is observed that the hard wood fiber–polypropylene composites, by using maleated polypropylene (MAH-PP), show comparatively better performance to soft wood fiber–polypropylene composites. Tensile strength and charpy impact strength have been increased to a maximum of 50 and 20%, respectively. The damping index has been decreased by 60% when 10% of MAH-PP has been used. Water absorption and scanning electron microscopy of the composites are also investigated.

Cell morphology of extrusion foamed poly(lactic acid) using endothermic chemical foaming agent

Poly(lactic acid) (PLA) was foamed with an endothermic chemical foaming agent (CFA) through an extrusion process. The effects of polymer melt flow index, CFA content, and processing speed on the cellular structures, void fraction, and cell-population density of foamed PLA were investigated. The apparent melt viscosity of PLA was measured to understand the effect of melt index on the cell morphology of foamed PLA samples. The void fraction was strongly dependent on the PLA melt index. It increased with increasing melt index, reaching a maximum value, after which it decreased. Melt index showed no significant effect on the cell-population density of foamed samples within the narrow range studied. A gas containment limit was observed in PLA foamed with CFA. Both the void fraction and cell-population density increased with an initial increase in CFA content, reached a maximum value, and then decreased as CFA content continued to increase. The processing speed also affected the morphology of PLA foams. The void fraction reached a maximum value as the extruders screw speed increased to 40 rpm and a further increase in the processing speed tended to reduce the void fraction of foamed samples. By contrast, cell-population density increased one order of magnitude by increasing the screw speed from 20 to 120 rpm. The experimental results indicate that a homogeneous and finer cellular morphology could be successfully achieved in PLA foamed in an extrusion process with a proper combination of polymer melt flow index, CFA content, and processing speed.

Microcellular Wood Fibre Reinforced PP Composites

Abstract Microcellular wood fibre reinforced polymers have practical significance given the possibility of reducing the density of automotive components due to their microcellular structure, as well as processing and performance advantages. A microcellular foaming process with a chemical foaming agent was applied at an experimental stage to injection moulding, extrusion and compression moulding of wood fibre reinforced polypropylene composites. The focus of the research was to investigate these processes using a chemical foaming agent and to perform comparative studies of the physico-mechanical properties of microcellular materials. The effects of the presence of the chemical foaming agent (exothermic) and variation of its content on density, microvoid content, mechanical properties (tensile and flexural), odour concentration and cell morphology of microcellular polypropylene-wood fibre composites were studied. The morphology, cell size, shape and distribution of the microcells were investigated using scanning electron micrographs. Injection moulding process produced finer microcellular structures in comparison with the other processes. As compared to the non foamed composites, the density reduced maximum 30% (0.741 g/cm3), 20% (0.837 g/cm3) and 22% (0.830 g/cm3) for the injection moulding, extrusion and compression moulding process respectively. The chemical foaming agent reduced the odour concentration in relation to the same non foamed composites. Injection moulding showed better performance in comparison with extrusion and compression moulding in terms of cell morphology, density reduction, odour concentration and mechanical properties.

Influence of different endothermic foaming agents on microcellular injection moulded wood fibre reinforced PP composites

Microcellular wood fibre reinforced polypropylene composites, a new development using bio-fibre strengthened plastic, were prepared in an injection moulding process. The influence of three different endothermic chemical foaming agents was examined. The effects of various concentrations (1 to 4 wt.% of the composites) of the chemical foaming agent on the properties of the composites was studied with a view to establishing the concentration-structure-property relationships for these materials. The influence of wood fibre type (hard wood and soft wood) on the microcellular structure and physico-mechanical properties of the composites was also investigated. Microcell morphology (cell size, shape and distribution) was observed using scanning electron microscope. The chemical substance of different endothermic foaming agent affected the microcellular structure of hard and soft wood fibre-PP composites. Endothermic foaming agent with chemical substance polymeric microsphere (ESC 5313) showed finer microcellular structures compared to other foaming agents and 4 wt.% content of chemical foaming agent exhibits finer microcellular structures than the other contents. The reinforcing of soft wood fibre showed significantly finer microcellular structures than the hard wood fibre reinforcements. Density reduced maximum 30% and decreased up to 0.721 g/cm3 at soft wood fibre 30 wt.% content with coupling agent maleic anhydride grafted polypropylene (MAH-PP). With the addition of MAH-PP, specific tensile strength and specific flexural strength increased maximum 60% and 55% respectively with foaming agent ESC 5313 at soft wood fibre 30 wt.% content.