PROCESSING STICKY COTTTON
The following article was published in Journal of Cotton Science volume 2002.
By Mr.Eric Hequet and
Mr.Noureddine Abidi, Ph.D.
In spinning mills, sticky cotton can cause serious problems. It contaminates the textile machineries like blow room , card, drawing, roving, and spinning frames. These contaminants are mainly sugar deposits produced either by the cotton plant itself (physiological sugars) or by feeding insects (entomological sugars), the latter being the most common source of stickiness.
Seventeen mixes having a moderate level of stickiness were evaluated in both ring and rotor spinning. High-performance liquid chromatography tests were performed on residues collected from the textile machinery to identify the types of sugars present. It was shown that among the sugars identified on raw fiber, only trehalulose exhibits higher percentages in the residues than on the fiber. During the fibers-to-yarn transformation, the flow of lint is submitted to different friction forces; consequently, the temperature of some mechanical elements may increase significantly and affect the thermal properties of the contaminated lint. After a sugar becomes sticky, the other sugars present on the lint, as well as other substances such as dusts, silica, etc., will stick to the lint and could cause unevenness in the flow of lint being drawn, such as lapping up on the rolls, nep-like structures, and ends-down.
Therefore, the thermal properties of the five sugars identified on the contaminated fiber and on the residues collected on the textile equipment were investigated. Among the sugars tested, trehalulose is the only one having a low melting point, around 48degre C. In addition, trehalulose is highly hygroscopic. After passive conditioning of dehydrated trehalulose at 65% ± 2% relative humidity and 21 degree C ± 1degree C for 24 h, the quantity of adsorbed water at equilibrium was found to be approximately 17.5%. This corresponds to three molecules of water adsorbed for each molecule of trehalulose. The combination of low melting point and high hygroscopicity could be the cause of the selective accumulation of this sugar on the textile equipment.
Stickiness is primarily due to sugar deposits produced either by the cotton plant itself(physiological sugars) or by feeding insects(entomological sugars) .Insects have been documented as the most common source of contamination in some studies . The analysis of honeydew from thecotton aphid and cottonwhitefly has shown that aphid honeydew contains 138.3% melezitose(C18H32O16) plus 1.1% trehalulose (C12H22O11),whereas whitefly honeydew contains 43.8%trehalulose plus 16.8% melezitose . Otherrelative percentages may occur, depending on the environmental or feeding conditions. Furthermore, stickiness is related to the type of sugars present on the lint. The authors showed that trehalulose and sucrose(C12H22O11),bothdisaccharides, were the stickiest sugars when added to clean cotton, while melezitose(trisaccharide), glucose (C6H12O6), and fructose(C6H12O6) (both monosaccharides) were relatively non-sticky.
Previous investigations wereconducted to elucidate the factors affecting the behavior of cotton contaminated with stickiness. In textile mills, the method mainly used to reduce the impact of stickiness is blending sticky cotton with non-stickycotton . Stickiness caused by honeydew depends on the relative humidity, which is a function of both water content and air temperature, in which the contaminated cotton is processed. Stickiness measured with the thermodetector is dependent on the relative humidity.Sticky cotton (with 1.2% reducing sugarcontent), when stored in high relative humidity(70degree F, 80% relative humidity, caused moreproblems during processing than the same stickycotton stored at low relative humidity 75degree F, 55% relative humidity. However, at low relativehumidity, the fibers are more rigid and will increase the friction forces creating static electricity . . Therefore, it will require more energy to draw the lint.
Stickiness has been reported to cause a build-up of residues on textile machinery, which may result in irregularities or excessive yarn breakage . When processing low to moderately contaminated cotton blends, residues will slowly build up, decreasing productivity and quality, and forcing the spinner to increase the cleaning schedule. Consequently, we decided to study the origin of the residues collected on the textile equipment after processing sticky cotton blends with low to moderate levels of contamination.
MATERIALS AND METHODS
We selected 12 commercial bales contaminated with insect honeydew on the basis of their insect sugar (trehalulose and melezitose) content and their stickiness as measured with the high-speed stickiness detector . In addition, five non-sticky bales from one module were purchased for mixing with the contaminated cotton, so that alternative stickiness levels in the mixes could be obtained. The 12 contaminated bales were broken and layered. Ten samples per bale were taken. Each sample was tested with a high-volume instrument (Model 900 Automatic, Zellweger Uster, ) and high-performance liquid chromatography
High-Speed Stickiness Detector
The high-speed stickiness detector is derived from the sticky cotton thermodetector , which was approved as a reference test by the International Textile Manufacturers Federation in 1994 . This thermomechanical method combines the effect of heat and pressure applied to a sample of cotton placed between two pieces of aluminum foil. When the temperature increases, moisture in the cotton vaporizes and is absorbed by the sticky spots, making them stick to the foil. The high-speed stickiness detector is an automated version of the sticky cotton thermodetector . Three replications were performed on each sample (10 samples per bale x three replications = 30 readings per bale).
The mechanical process used in this study is described in Fig. 1. Opening, carding, drawing, roving, ring spinning, and rotor spinning machines used were all industrial equipment. In the ring spinning trial, the yarns were spun to a 19.68 x 10-6 kg m-1 (19.68-tex or 30 English number) count. Fourteen spindles were used for each mix spun, and each mix was run for 72 h. For the open-end spinning trials, the yarn produced was 26.84 x 10-6 kg m-1 (26.84-tex or 22 English number); 10 positions were used, and each mix was run for 20 h.
We ran preliminary tests on ring spinning before testing the mixes. A 13.6 kg sample of lint from each bale was carded and drawn. If noticeable problems occurred at the draw frame, the process was stopped. If not, the drawing slivers were transformed into roving. If noticeable problems occurred at the roving frame, the process was stopped. If not, the roving was transformed into yarn at the ring spinning frame. If noticeable problems occurred at the ring spinning frame, the process was stopped. If not, 45.4 kg of lint was processed for the large-scale test. If noticeable problems occurred at any step of the process, the cotton was mixed with 50% non-sticky cotton and the process was repeated. This procedure was used for 17 large-scale tests.
Four bales were spun without mixing the lint with the non-sticky cotton. Four bales were spun after mixing the lint with 50% non-sticky cotton. Four bales were spun after mixing the lint with 75% nonsticky cotton. Three bales were spun after mixing the lint with 87.5% non-sticky cotton. Finally, two baleswere spun after mixing the lint with 93.75% nonsticky cotton. Card slivers, flat wastes, draw frame residues, and sticky deposits collected at the end of each test on the rotor spinning and ring spinning frames were analyzed by high-performance liquid chromatography. These tests quantify the amount of sugars, expressed as a percentage of total sugars present. In addition, high-speed stickiness detector measurements were made on card slivers. After each spinning test was completed, the opening line and the card were purged by processing a non-contaminated cotton, then all the equipment was washed with wet fabric and thoroughly dried.
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