A Review on Coir Fibre, Coir Fibre Reinforced Polymer Composites and Their Current Applications

Coir fibre has generated much interest as an eco-friendly, sustainable fibre with low density. This review findings show that coir fibres are abundant, with an average global annual production of 1019.7 × 103 tonnes, with about 63% of this volume produced from India. Extraction of coir has been carried out through water retting. However, the retting period has been limited to 4–10 months. The lignin content of coir is more than 60% higher than that of other natural fibres; hence, coir could double as a source of lignin for other applications. The diameter of coir fibres varies from 0.006 mm (Vietnam) to 0.577 mm (Thailand), and their tensile strength ranges from 68.4 MPa (Tanzania) to 343 MPa (Vietnam). Coir fibres from Vietnam and India exhibit the highest elongation at break (63.8%) and the highest Young’s modulus (6 GPa), respectively. More than 50% of the researchers within the scope of the reviewed studies employed the hand layup (HLU) manufacturing method with an epoxy resin matrix. Fibre volume fractions used range between 10%–65%. An outstanding tensile strength of 62.92 MPa at 49% fibre volume fraction was recorded for coir composites where the fibres were unidirectionally oriented and stacked in three layers, manufactured using epoxy resin and the HLU technique. Only a few works have been done using Vacuum-assisted resin transfer moulding (VARTM). The curing of composites was mostly carried out at an unspecified temperature and duration. A defined fibre volume fraction with a defined mixing and mixing time of the matrix is imperative. The degree of uniform dispersity of the fibres in the matrix is lacking. The creep behaviour of coir composites, coating and wider treatment parameters need to be explored for advanced applications. Recent findings on the applications of coir composites are equally highlighted. © 2024 The Authors.