Life cycle assessment of wood-fibre-reinforced polypropylene composites

Composites of polymers reinforced with natural fibres have received increasing attention. Natural fibres such as sisal, flax, jute and wood-fibres possess good reinforcing capability when properly compounded with polymers. These natural fibre-reinforced composites find a wide array of applications in the building and construction industry and the automobile industry. The use of natural fibres in composite materials does not automatically make it a “sustainable material”, i.e. “natural” may not necessarily equal “environment friendly”. The literature in the field of natural fibre-reinforced composites with respect to their environmental standing is reviewed in this paper. A life cycle assessment has been carried out for wood-fibre-reinforced polypropylene composite preforms produced by compression moulding in comparison with those of polypropylene. Three levels of fibre contents, 10%, 30% and 50% by mass, have been used. The level of environmental impact caused by transportation is also studied. This study introduces a new term called “material service density”, which is defined as the volume of material satisfying a specific strength requirement (tensile strength in this study). The rationale behind this is that specific volumes of different materials are required to withstand a given mechanical load (tensile load in this case). Comparison of the material service density for two materials: wood-fibre-reinforced composite and polypropylene are conducted. The results showed that when material service density is used as the functional unit, wood-fibre-reinforced composite demonstrated superior environmental friendliness compared to polypropylene.