pressure on the environment because ASR is generally landfilled. On one hand, this opens the opportunityto produce greener automotive materialsthat are cost-effective to dismantle and dispose of (either by recycling, incineration, compostability, pyrolisys, or other means). On the other, it raises new challenges to increase the performance and cost competitiveness of current “green” materials, set up a wider network of infrastructure for the reception, de-polution, dismantling, sorting and disposal of ELVs, create competitive markets for the recovered/recycled materials from ELVs and enforce a common environmental legislation platform which assist OEMs to satisfy national and internationallegislationin terms of end-oflife waste disposal.
Lignocellulosic Fibre-Reinforced “Green” and “Truly Green” Composites “Green” and “truly green” composites are being developed worldwide. It is generally accepted that “green” composites consist of natural fibres and biopolymers, with the latter usually produced from petrochemicalor renewablesources.4, 5“Truly green” composites incorporate renewable sourced biopolymers produced from celluloseand soy-based plastics, starch, lactic acid, polyhydroxyalkanoates, bacterialcellulose, soy-based plastics, among others5, usually reinforced with plant fibres, specificallylignocellulosicfibres. According to its origin, natural fibres can be classified as vegetable, animal or mineral. Vegetable fibres may be extracted from wood (e.g. softwood and hardwood), husk (e.g. maize, rice and wheat), fruit (e.g. coir, luffa), seed (e.g. cotton), leaf (e.g. henequen, sisal), stalk/bast (e.g. abaca, flax and hemp), cane or grass (e.g. bamboo). Lignocellulosic fibres, are composed of cellulose, hemicelluloses and lignin with small amounts of different free sugars, hollocelluloses, starch, pectins, proteins, several mineral salts and extractives, such as waxes, fatty alcohols, fatty acids and different esters. The wide availability, low cost, renewable and thermally recyclable properties, low carbon foot print and sound damping properties of lignocellulosic fibres underpin its use in fibre-reinforced composite applications. Lignocellulosic fibres have lower mechanical
The wide availability, low cost, renewable and thermally recyclable properties, low carbon foot print and sound damping properties of lignocellulosic fibres underpin its use in fibre-reinforced composite applications.
Some statistics show that approximately five to six percent of the entire passenger vehicle fleet in Canada reaches end of its useful life every year. properties than competing synthetic reinforcing fibres; however, their lower density and thus specific properties, are comparable to those of glass fibres. Lignocellulosic fibres have extraordinarily high potential as reinforcing elements in composite materials because the tensile strength and Young’s modulus of the I-cellulose crystal that forms the crystalline regions of cellulose reaches values that are either similar or superior to those of glass fibres (~10 GPa6 and between ~78 to 128 GPa7, 8 respectively). According to some studies, the substitution of glass fibres for hemp fibres in automotive fibre-reinforced composites has the potential to save approximately 1.4 kilogram of carbon dioxide per each kilogram of glass fibres replaced, during the whole life cycle of the part until its disposal.9 A number of potential applications for lignocellulosic-based materials are found in interior and exterior automotive applications where stiffness and low cost are among the required criteria,10 e.g. thermo-acoustic insulation panels in undermats, door panels, tailgates and composite systems. New higher performanceapplicationswill be developed as “green” and “truly green” lignocellulosicfibrereinforcedmaterialsimprove several technical issues, mostly inherent to lignocellulosic fibres, including low fibre-matrix wettability and adhesion, hydrophilic behaviour and
quality variability. Regular increases in the use of lignocellulosic fibres as fillers and reinforcements for thermoplastics and thermosets in the automotive industry can be expected for years to come. For example, the German automotive industry used more than 19,000 tons of hemp (Cannabis sativa) and flax (Linum usitatissimum) fibres in 2005, whereas in 1999 this amount accounted only for 9,600 tons.9
Variability of Lignocellulosic Fibres One of the major drawbacks of lignocellulosic fibres is their quality variability, which is in part due to the presence of non-cellulose compounds.11 The removal of non-cellulose compound from lignocellulosic fibres improves their compatibility with dyes, thermal resistance, chemical composition and mechanical properties. This is achieved by traditional mechanical, bacterial/enzymatic, physical or chemical processes, including fibre surface modification methods. Alternative methods are also being developed, for example, to reduce the amount of lignin using genetic manipulation.12 During the growth and harvest of the lignocellulosic crop factors such as the fibre crop variety, soil conditions, climate, location, the section of the crop from which the fibres are extracted from and the harvest june 2009 Canadian Chemical News 15