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  • Maturity

    Chapter 2 - Cotton value addition - The impact of cotton fibre properties on textile 


    Maturity, which is largely determined by growing conditions, can be defined as the relative wall thickness (i.e. the area of the cell wall to that of a circle with the same perimeter as the fibre, or the ratio of the cell wall thickness to the overall ‘diameter’ of the fibre). Cross sections of fibres of different maturity are shown in figure 2.13.




    Maturity generally has a greater effect on fabric appearance and defects than any of the other fibre properties. It is commonly measured by the double compression airflow test, although single fibre measurements (e.g. AFIS) are used for more detailed information, including maturity distribution and the presence of immature and dead fibres. Different means of expressing maturity are in use, the two most popular being the percentage maturity (Pm) and maturity ratio (M), a level of at least 0.9 (preferably 0.95) for M and 80% for Pm being desirable. Cotton fibre maturity greatly affects nep formation, dye uptake and dyed appearance. Variations in maturity within a yarn batch or fabric can lead to streakiness and barré because of differences in dyed appearance. It is, however, not only the average maturity which is important but also the distribution of maturity. A small percentage of immature or ‘dead’ fibres may not significantly affect the average maturity but could significantly affect the yarn and fabric appearance, notably in terms of neppiness and white flecks which can comprise only about 0.5% (by weight) of fibres. The lighter appearance of dyed immature fibres is mainly due to their flat and ribbon-like non-uniform shape and the shorter path-length the light takes through the thinner dyed wall, rather than due to a lower dye uptake, with the difference in light reflectance characteristics from the ‘flat’ fibre surfaces also playing a role (e.g. shining neps). Nevertheless, the rapid desorption of dye from immature fibres may also play a role. Scouring and finishing losses are also greater for immature cottons, because their non-cellulosic contents are higher. Fibre maturity also affects lustre. Immaturity can also be associated with stickiness and roller lapping because of excessive plant sugars, particularly under high humidity conditions. Combing is known to remove relatively immature and fine fibres.