Conventional and unconventional chemical treatment methods of natural fibres for sustainable biocomposites

Natural fibres could be used as one of the raw materials for the production of engineering materials. They have the advantage of low density, light weight, biodegrability and the capacity to reprocess to a certain extent. There are certain limitations of such fibres when formed composites with synthetic polymers like high degree of moisture absorption, and lack of affinity between fiber and the matrix. The presence of polar components like hemicellulose and lignin content in the fibres are the reason for these materials to be hydrophilic. This issue has been addressed by treating fiber surface with variety of chemical reagents which is reported to improve mechanical and adhesion property between fiber and the matrix. Chemical treatments can be based on reactions involving esterification methods like acetylation and benzylation, graft polymerization methods like treatments with triazine, isocyanates and maleic anhydride, silane coupling agents, other treatments include alkali, acrylation and acrylonitrile, permanganate, peroxide treatments and also steric acid, sodium chloride and oleoyl chlorite. Surface modification of fibres reduces its moisture absorption tendency and improves their mechanical properties thereby increasing durability of the composites.