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This century has witnessed remarkable achievements in green technology in material science through the development of natural fiber reinforced composites. The development of high performance engineering products made from natural resources is increasing worldwide day by day. There is increasing interest in materials demonstrating efficient use of renewable resources. Nowadays, more than ever, companies are faced with opportunities and choices in material innovations. Due to the challenges of petroleumbased products and the need to find renewable solutions, more and more companies are looking at natural fiber composite materials. The primary driving forces for new biocomposite materials are the cost of natural fibers (currently priced at onethird of the cost of glass fiber or less), weight reduction (these fibers are half the weight of glass fiber), recycling (natural fiber composites are easier to recycle) and the desire for green products. This Review provides an overview of natural fiber reinfocred composites focusing on natural fiber types and sources, processing methods, modification of fibers, matrices (petrochemical and renewable), and their mechanical performance. It also focuses on future research, recent developments and applications and concludes with key issues that need to be resolved. This article critically summarizes the essential findings of the mostly readily utilized reinforced natural fibers in polymeric composite materials and their performance from 2000 to 2013.

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SYNOPSISStudies on structure and properties of natural vegetable fibers (NVF) show that composites made of NVF combine good mechanical properties with a low specific mass. The high level of moisture absorption by the fiber, its poor wettability, as well as the insufficient adhesion between untreated fibers and the polymer matrix lead to debonding with age. To build composites with high mechanical properties, therefore, a surface modification of the fibers is necessary. The existing physical and chemical NVF modification methods-e.g., plasma treatment or graft copolymerization-which are used for the development of NVF-polymer composite properties is discussed. It is shown that modified cellulose fiber-polymer interaction mechanisms are complex and specific to every definite system. By using an coupling agent, like silanes or stearin acid, the Young's modulus and the tensile strength increases, dependent on the resin, until 50%. Simultaneously, the moisture absorption of the composites decreases for about 60%. With other surface modifications, similar results are obtained. 0 1996 John Wiley & Sons, Inc I NTRO DUCT10 N Fiber-reinforced plastics are structural composites, in which a polymer matrix is combined with fibers, fabric cuttings, or filling webs. In conventional composites, the fibers are made of glass, aramid, or carbon. The advantage of fiber-reinforced plastics results from their structure. The controlled structure in which the fibers are lying in the polymer matrix increases the strength and the stiffness of the composite. At present, natural vegetable fibers (NVF) are used in composites, where high strength and stiffness are not of first priority. NVF reduce the mass of the composite, because they have a low density. Their production is economical, with low requirements on equipment, and they can easily be recycled.Conventional fibers (glass, aramid, carbon, etc.) can be produced with a definite range of properties. The characteristic properties of NVF vary considerably. This depends on whether the fibers are taken

Abstract. Flax fibre was modified with acetylation. The influence of the acetylation on the structure and properties of flax fibre were investigated as well as modified flax fibre reinforced polypropylene composites were also prepared. The catalyst was used to accelerate acetylation reaction rate. Flax fibre was characterised after modification. Surface morphology, moisture absorption property, components content, degree of polymerisation, crystallinity of cellulose and thermal stability of flax fibres were studied. Due to acetylation, the flax fibre surface morphology and moisture resistance properties improved remarkably. Flax fibre (modified and unmodified) reinforced polypropylene composites were fabricated with 30 wt% fibre loading. The mechanical properties were investigated for those composites. Tensile and flexural strengths of composites were found to increase with increasing degree of acetylation up to 18% and then decreased. Charpy impact strengths of composites were found to decrease with increasing degree of acetylation. Owing to addition of coupling agent (maleated polypropylene -MAH), the tensile and flexural strength properties were found to increase in between 20 to 35% depending on degree of acetylation.

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SYNOPSISStudies on structure and properties of natural vegetable fibers (NVF) show that composites made of NVF combine good mechanical properties with a low specific mass. The high level of moisture absorption by the fiber, its poor wettability, as well as the insufficient adhesion between untreated fibers and the polymer matrix lead to debonding with age. To build composites with high mechanical properties, therefore, a surface modification of the fibers is necessary. The existing physical and chemical NVF modification methods-e.g., plasma treatment or graft copolymerization-which are used for the development of NVF-polymer composite properties is discussed. It is shown that modified cellulose fiber-polymer interaction mechanisms are complex and specific to every definite system. By using an coupling agent, like silanes or stearin acid, the Young's modulus and the tensile strength increases, dependent on the resin, until 50%. Simultaneously, the moisture absorption of the composites decreases for about 60%. With other surface modifications, similar results are obtained. 0 1996 John Wiley & Sons, Inc I NTRO DUCT10 N Fiber-reinforced plastics are structural composites, in which a polymer matrix is combined with fibers, fabric cuttings, or filling webs. In conventional composites, the fibers are made of glass, aramid, or carbon. The advantage of fiber-reinforced plastics results from their structure. The controlled structure in which the fibers are lying in the polymer matrix increases the strength and the stiffness of the composite. At present, natural vegetable fibers (NVF) are used in composites, where high strength and stiffness are not of first priority. NVF reduce the mass of the composite, because they have a low density. Their production is economical, with low requirements on equipment, and they can easily be recycled.Conventional fibers (glass, aramid, carbon, etc.) can be produced with a definite range of properties. The characteristic properties of NVF vary considerably. This depends on whether the fibers are taken