Contents -
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1.1 Introduction
Cotton fibers are the purest form of cellulose, nature’s most abundant polymer. Nearly 90% of the cotton fibers are cellulose. All plants consist of cellulose, but to varying extents. Bast fibers, such as flax, jute, ramie and kenaf, from the stalks of the plants are about three-quarters cellulose. Wood, both coniferous and deciduous, contains 40–50% cellulose, whereas other plant species or parts contain much less cellulose. The cellulose in cotton fibers is also of the highest molecular weight among all plant fibers and highest structural order, i.e., highly crystalline, oriented and fibrillar. Cotton, with this high quantity and structural order of the most abundant natural polymer, is, not surprisingly, viewed as a premier fiber and biomass. This chapter focuses on the chemical structure of cotton fibers and its structural relationship to cellulose synthesis, fiber development and dehydration as well as other chemical and structural aspects (physical properties, dyeing and finishing) not dealt with in the following chapters. Cotton fiber cells are developed in four overlapping but distinct stages of initiation, elongation, secondary cell wall thickening and maturation and desiccation (Naithani et al., 1982). Structural development and properties of cotton fibers during the primary wall formation (elongation) and secondary wall thickening (cellulose synthesis) as well as during desiccation (transition from mobile to highly hydrogen-bonded structure) are detailed. |