ASTM D8394-21 PDF

SIGNIFICANCE AND USE 5.1 Cotton fiber that is on average finer and more mature is more desirable than coarse or immature fiber, although distinction between these qualities cannot be made quickly and accurately using current test methods. Immature fibers break more easily during processing and have a tendency to form into neps (small entanglements) during processing in the spinning mill. These consequences adversely affect yarn and fabric quality and appearance. Yarn and fabric produced from immature fiber is typically also less lustrous and does not take up dye consistently so yarn and fabric appearance may be different after dyeing. 5.2 Maturity has a high positive correlation with fiber length and strength but genetic differences and differences in fiber wall thickness caused by plant diseases, soil, and water conditions during the growing season interfere with this relationship. 5.2.1 Fine fibers are required for fine count yarn manufacture and fiber fineness affects yarn count, evenness and strength. Both fineness and ribbon width are strong genetic traits evident between species and affected by growing conditions within species. 5.2.2 Micronaire has traditionally been used as a measure of fiber fineness although the value actually measures fiber specific surface area or surface area per unit weight. As a result, micronaire varies concomitantly with both maturity and fineness (see Fig. 2). Maturity and fineness are related to micronaire via Lord’s equation.4 FIG. 2 Relationship Between Micronaire (X), Fineness (H), and Maturity (M) 5.3 Cottonscope values have been judged against fineness, maturity and ribbon width values produced by examination of thousands of individual, magnified fiber cross-sections. Relationships with equivalent values by these and other older test methods are highly significant5,6 particularly if the number of cross-sections analyzed is high (>3000) and the cross-sections are carefully prepared and measured. Cottonscope measures approximately 20,... SCOPE 1.1 This test method covers the determination of linear density (gravimetric fineness hereafter stated as fineness), maturity, micronaire, and ribbon width of cotton fibers from a loose, chemically untreated sample taken before harvest, during ginning, during mill processing or unraveled from raw (undyed) yarn or fabric. 1.2 This test method requires the use of an integrated instrument, for example, the Cottonscope (see Fig. 1), that measures the maturity, fineness, ribbon width, and micronaire of cotton fiber.2 FIG. 1 Cottonscope Instrument Note 1: For another test method to determine the maturity of cotton fibers, refer to Test Method D1442. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.