Secondary Natural Fibres in Green Composites

Materials like plastics, concrete, derivatives of petroleum and metals such as steel that have various commercial and industrial uses all over the world. These materials have a large carbon footprint and present a grave waste disposal problem. The use of these non-renewable materials must be reduced to address the growing environmental crisis. It is important to find naturally based materials that have low density and high durability to replace traditional composites. Green composites are a combination of two or more materials out of which one or all may be derived from plant sources [1]. This reduces the carbon footprint of the material and increases its biodegradability. In the current scenario, many “green composites” are composed of petroleum-based matrices such as epoxy resins. However, these composites do not provide an environmentally sustainable solution as their recycling processes involve extensive procedures. Alternatives such as bio-based epoxy resins show promising approaches. Biopolymers such as poly-lactic acid, block copolymers, and bio-based nano-fillers such as carbon nanomaterials can be used to increase the toughness of eco-epoxies. Recently epoxies have also been developed from other renewable sources such as rosin, furan, lignin and itaconic acid [2-4]. The matrix imparts shape to the composite, distributes the stresses among the fibres and protects the fibres from environment exposure and is thus responsible for its durability. The fibres are responsible for the mechanical strength of the composite. Secondary fibres prove to be more advantages due to greater abundance, easy and local availability, cheaper cost, safe handling and play an important role in waste management and efficient resource generation schemes apart from also possessing other advantages of natural fibres such as low density, high durability and strength, and a reduced carbon footprint [5]. Natural fibres act as very effective reinforcements in polymer matrices by providing mechanical and flexural strength. A recent study estimates that about 30,000,000 tonnes of natural fibres derived from plant and animal resources are produced over the world annually [6]. Plant fibres are classified as primary and secondary. This review is an overview of largely produced secondary natural fibres, obstacles in using natural fibres and recent advancements in techniques to improve its applications.