Textile Industry Needs Christopher D
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The Journal of Cotton Science 21:210–219 (2017) 210 http://journal.cotton.org, © The Cotton Foundation 2017 ENGINEERING & GINNING Textile Industry Needs Christopher D. Delhom, Vikki B. Martin, and Martin K. Schreiner ABSTRACT lthough the immediate customer of the gin is Athe cotton producer, the end user of the ginned The immediate customers of cotton gins are lint is the textile mill, retailers, and eventually the the producers; however, the ultimate customers consumer. Thus, it is essential for the ginner to are textile mills and consumers. The ginner has satisfy both the producers and the textile industry. the challenging task to satisfy both producers and Consequently, the ginner needs to be aware of the the textile industry. Classing and grading systems needs of the textile industry. are intended to assign an economic value to the The intent of the cotton classing and grading bales that relates to textile mill demands and the system is to assign an economic value to the bale that quality of the end product. International textile documents its properties as it relates to the quality of mills currently are the primary consumers of U.S. the end product. Since the last edition of the Cotton cotton lint where it must compete against foreign Ginners Handbook in 1994, the customers of U.S. origins. International textile mills manufacture cotton have changed radically, shifting from primar- primarily ring-spun yarns, whereas domestic mills ily domestic to international mills. International mills manufacture predominantly rotor spun yarns. Pro- have been accustomed primarily to hand-harvested ducers and ginners must produce cottons to satisfy cotton that has been processed at slow ginning all segments of the industry, i.e., domestic and in- rates. The international mills are predominantly ternational. Many fiber quality attributes are im- producing ring-spun yarns, whereas U.S. mills are portant to the textile industry including those that dominated by rotor spinning (International Textile are included in HVI-based classing, i.e., strength, Manufacturers Federation, 2014). The overall need length, micronaire, trash, and grade. There are for well-ginned, clean, dry cotton remains; however, other important fiber quality attributes that are not the specific fiber properties required for both spin- included in HVI-based classing such as short-fiber ning systems differ. Therefore, it is more important content, fiber maturity, stickiness, fiber cohesion, than ever that ginners minimize fiber damage while and neps. The general steps of textile processing: reducing non-lint content to maximize market value. opening, cleaning, carding, drawing, spinning, and When the last edition of the Cotton Ginners fabric production have not changed in many years. Handbook was published, more than half the annual However, manufacturing systems have become cotton production in the U.S. was consumed domesti- highly automated, and production speeds have cally. Currently, less than a third of the production is dramatically increased. Contamination-free cotton consumed domestically and two thirds are sold on has always been important to the textile industry, international markets where the cotton must compete but recent changes in harvesting systems in con- against foreign origins (USDA-ERS, 2015). U.S. junction with higher production speeds and global cotton must compete against hand picking and low competition from synthetic fibers and other growths labor costs while commanding a premium price to of cotton have increased the industry demand for enable the U.S. cotton producer to thrive. contamination-free cotton. The ginner plays a vital Textile manufacturers purchase cotton that has role in preserving and improving the quality of a level of quality that most closely matches the cotton to meet the demands of the textile industry. intended end use. All cottons cannot be used for all end products. Generally, lighter weight textile products require higher quality cotton because finer yarns are needed to produce lighter weight textiles. C.D. Delhom*, USDA-ARS Cotton Structure and Quality Research Unit, 1100 Robert E. Lee Blvd., New Orleans, LA For example, sheeting and shirting yarns are much 70124; V.B. Martin and M.K. Schreiner, Cotton Incorporated, finer in weight per unit length (higher count) and 6399 Weston Parkway, Cary, NC 27513 therefore require cleaner, longer cotton fibers with *Corresponding author: [email protected] better length uniformity, fineness, and strength. DELHOM ET AL.: TEXTILE INDUSTRY NEEDS 211 Coarser yarns (lower count) such as those used in removed easily, whereas smaller particles (pepper denim are more tolerant of short-fiber content and trash) are difficult to remove and can cause imper- non-lint content in the bale, but still require fine and fections in the yarn. Some of the trash particles are strong fibers. actually seed coat fragments and/or pieces of bark and grass. Color can serve as an indicator of field IMPORTANT FIBER PROPERTIES weathering or excess moisture content during har- vesting and/or seed cotton storage. Color is an impor- For textile processing the following properties tant consideration for the mill to be able to produce are critical; most, but not all, of these are measured yarn that is uniform in appearance and performance. with High Volume Instrument® (HVI)-based class- ing system. Not Included in HVI-Based Classing: Short-Fiber Content. Short-fiber content (by Included in HVI-Based Classing: weight or by number) is defined in the U.S. as the Fiber Strength. The strength of cotton fibers percentage of fibers shorter than one-half inch (12.7 (weight normalized force-to-break) is measured by mm). It has a major effect on how the cotton pro- HVI and reported in grams of force per tex. A tex cesses, yarn strength, and evenness. Short fibers are is equal to the weight, in grams, of 1,000 m of fiber. fundamentally unspinnable fibers. A large percentage Strength has improved since the last edition of this of short fibers might be removed by the mill depend- handbook so that upland cottons typically range ing on the end product. This will result in increased from 28 to 32 g/tex to 42 to 46 g/tex for pima cottons. waste at the mill and reduced profitability. Fiber Length. Length is expressed as the upper- Maturity. Mature cotton is cotton that has half mean length (UHML) of a fiber beard. UHML a fully developed secondary cell wall. Immature is the mean length by number of the longer one-half fibers, commonly known as dead fibers, can lead to of the fibers by weight (ASTM D123). Uniformity dyeability issues and increase neps count (entangle- index (UI) is a measure of length uniformity. It is ments of fiber). Maturity variation in fabrics can lead the ratio of the mean fiber length to the upper-half to appearance defects such as barré (color banding mean length. UHML of commercial upland cottons in fabrics) and white specks (small undyed specks typically ranges from 1.08 to 1.24 inches (27.4-31.5 in finished fabrics). The ginner has no control over mm), and pima cottons typically range from 1.36 maturity, although immature cotton will be prone to 1.43 inches (34.5-36.3 mm). UI of commercial to nep formation and fiber breakage during ginning upland cottons typically ranges from 80.0 to 82.5% (Anthony et al., 1988). and pima cottons typically range from 85.0 to 86.5%. Neps. Immature cotton fibers tend to be flat Micronaire. Micronaire is an indirect measure- and create entanglements known as neps. Long and ment of fiber fineness and maturity. Fiber fineness fine fibers also tend to entangle when submitted to limits how many fibers can be in the cross-section mechanical processing. For this reason, longer cot- of a given size yarn, whereas maturity has a direct tons are generally handled more gently than shorter relationship with fibers tensile properties and perfor- cottons. Immature cottons can form neps during mance in dyeing. Upland cotton micronaire typically all processing stages from harvesting until carding. ranges from 3.9 to 4.9 and pima cottons typically Most neps are removed during carding and textile range from 3.7 to 4.2. mills aim to reduce nep levels by 80 to 90% during Trash and Grade (Leaf and Color). Previously, the process. Nep levels vary greatly based on grow- the classer assigned the grades with the assistance ing region, harvesting, and ginning techniques. Nep of HVI. In recent years, grades are assigned solely levels are of particular importance for pima cotton by the HVI instrument, with instrument color grade and a goal of fewer than 200 neps per gram in the beginning in 2000 and instrument leaf grade begin- bale is desired by textile mills. ning in 2011 (Knowlton, 2014). HVI measures both Stickiness. The form of stickiness that mainly trash particle count and percent trash area, which is impacts spinning mills is commonly called hon- used to determine leaf grade. Color grade is based eydew. It is an excess of sugar droplets on the lint on measured reflectance (Rd) and yellowness (+b). due to insect activity. In extreme cases, the sugars Trash content has a direct bearing on how well the can build up on processing equipment and slow or cotton processes in the mills. Large particles can be even shut down production in a spinning mill. The JOURNAL OF COTTON SCIENCE, Volume 21, Issue 3, 2017 212 principal causes of stickiness of entomological origin are due to whitefly or aphid infestations (Hequet and Abidi, 2006). Another cause of stickiness is due to excessive seed-coat fragment contamination due to a buildup of seed meat and oil residue. Fiber Cohesion. This is the property that con- trols friction between fibers and affects the manner fibers slide past each other in carding, drawing, and spinning.