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ABSTRACT
Skeins of yarns spun from a wide range of cottons are dewaxed by Soxhlet extraction with ethanol. After drying, their mechanical properties are determined by single yarn tensile tests. Dewaxing produces a significant increase in yarn tenacity and a slight decrease in elongation at break. Yarn tensile properties are regressed on data sets of fiber properties that include wax content. Yarn strength is explained primarily by fiber strength and fiber fineness, although fiber strength and Micronaire value provided a reasonably good estimate. Wax content, which appears to be closely related to the specific surface area of the fiber, and hence Micronaire value, fails to qualify for entry into regression equations for yarn strength.
This is the second of two reports addressing the influence of wax content on cotton fiber characteristics and yarn tensile properties. We initiated it in response to enquiries from cotton breeders who wished to better understand the relationships between fiber characteristics and yarn properties.
The wax of cotton fibers is chemically complex, containing acids and alcohols of high molecular weight [1]. Despite its heterogeneity and concentration variation in cotton samples, its constitution has been shown to be quite similar, even though the origins of the cottons range from South America to Egypt, India, and the U.S.A. [4]. Only the Indian cottons were reported to have significantly different wax characteristics [5]. Nevertheless, wax appears to be very effective in assuring sufficient cohesion for web formation at the card and drawframe, while allowing fibers to slide over themselves during drafting processes. Lack of wax causes problems in textile processing, as evident when bleached cotton is used without adding a lubricant.
Fiber-to-fiber frictional forces can be expected to have a role in determining the tensile behavior of yarns. Even simplified formulas derived by classical mechanical analyses [8] contain terms that involve the coefficient of friction. Presumably the inability to rapidly measure this parameter has contributed in part to the use of empirically derived constants instead of terms involving the coefficient of friction. An indirect measure of friction in the form of wax content may be expected to be a useful means of improving the accuracy of equations used to estimate yarn tensile properties.
Procedure
Thirty-six cottons exhibiting a wide range of genetic...