Cotton fibre elongation: a review

The tensile properties of cotton are essential quality traits for determining the performance of a material in textile processing. Characterization of the tensile properties of cotton has evolved from manual assessments by a human to a diverse series of mechanical methods. The early techniques of characterizing tensile properties of fibres were carried out using modified yarn testing equipment and bundles of cotton fibres. In the mid-twentieth century, instruments specifically designed to measure the tensile properties of cotton fibres were developed and adopted by the industry. The early developments in fibre-specific instruments utilized a flat bundle approach that dominated the industry until the advent of high-speed cotton testing with the High Volume Instrument (H.V.I.) implementation in the later part of the twentieth century. The H.V.I. utilizes a tapered beard approach to arranging the fibres for testing. Although tensile properties consist of breaking strength and elongation, the focus has been mainly on breaking strength. The textile industry recognized the importance of elongation early on. However, the difficulties in measuring the relatively small breaking elongations with accuracy, precision, and efficiency relegated the measurement to an afterthought. Modern high-speed testing has made elongation testing practical; however, the lack of calibration materials limited the use of elongation in comparing results. The recent development and implementation of elongation calibration cottons for high-speed tensile testing has renewed interest and restored the feasibility of characterizing cotton for strength and elongation. The history of characterizing cotton fibre tensile properties is reviewed from manual to modern high-speed automated testing. The relationship between fibre strength and elongation is discussed for single-fibre and bundle testing. Approaches to assess the tensile properties of cotton, such as considering the modulus and the work-to-break, are discussed. Factors that may influence fibre elongation, such as genetics and environment, are discussed, and the influence of elongation on textile processing and quality.