What is Cotton stickiness ?

The thorn in the side of the cotton producers and particularly of the spinners, is the notorious honeydew. This term defines the dreadful stickiness of cotton fibres due to the contamination by two terrible insects: the cotton aphid and the white fly, which last is widely spread in case of long dry spells. The researchers have intensified their efforts to control the reproduction of these insects in the last years, during which this infestation increasingly expanded. This spreading of the phenomenon is demonstrated by the result of a survey carried out by ITMF (International Textile Manufacturers' Federation) with 201 spinning mills in 22 countries all over the world about raw cotton contamination: a good 27% of the answers reported as serious the problem of cotton stickiness originated by honeydew, and Sudan was leading the high-risk countries.

Trials are under way to identify the honeydew-affected cotton batches through:

- the analysis of the sugary substances in the honeydew, which cause the cotton stickiness;

- the development of tests on the spot in order to detect the presence of sticky cotton types.

Specific treatments to neutralise cotton stickiness due to honeydew were also studied. Already in 1988 J. Gutnecht explained the results of stickiness tests carried out by ″Minicard″ method to show the influence of the relative humidity in the spinning room on the potential stickiness of a wide range of sticky cotton types and on various blends of sticky and non-sticky materials. At the same time he presented a new thermal method, simpler and less expensive than the Mini-card test, which results correlate pretty well with the Minicard System.

To remove stickiness from cotton fibres, various systems have been used:

- spraying of chemical substances on the fibres, which however causes some problems in subsequent processing

- passage of cotton bales or of a web of opened fibres through high frequency ovens.

In the past years a project was presented by R. Demuth to eliminate the cotton stickiness caused by honeydew. The project consisted in two phases: washing of the fibre with water and detergent with subsequent mild drying followed by thorough drying of cotton in a microwave tunnel, so that the adhesive substances become brittle and are reduced to powder. These systems however are not sufficiently cost-effective, so that there is a trend to dispose of the sticky cotton by mixing it in small percentages with the regular cotton.

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Minimizing Stickiness from Imported Cotton

Minimizing Stickiness from Imported Cottons by Using Chemical Additives and their Ultimate Effect on Tensile Properties of Yarn

The contamination of honeydew (stickiness) is a serious problem with the imported cottons used by the local textile industry. In case of heavy stickiness, the contaminants may continue to accompany the fiber through fiber processing and ultimately affect the yarn quality especially its tensile properties. The use of chemical additives is reported as an effective technique for minimizing the cotton stickiness. This paper reports the effect of different additives at variable concentrations on stickiness level and tensile properties (lea-strength, single yarn strength, elongation & count lea strength product value) of the spun yarn of two imported cotton varieties (Sudani & American Pima). Results showed that the additives and additive concentrations had highly significant effect on the tensile properties of the spun yarn. The yarn properties were degraded by increasing the concentration of the additives.

Key Words: Cotton stickiness; Cotton contamination; Chemical additives; Yarn strength; Yarn elongation

INTRODUCTION

Cotton stickiness becomes apparent when the contaminants present on the cotton fibres began to obstruct with the normal operation of the spinning processes (Khalifa, 2001). These contaminants are the sticky sugar deposits produced either by the insects (for example white fly & aphids) or by the cotton plant itself (Abidi & Hequet, 2005). These deposits are often referred to as honeydew (Gutknecht et al., 1986) and it is the main source of sugars that can result in sticky lint. Sticky cotton is a worldwide problem. In some cotton growing regions, the potential to produce sticky cotton is always present (Khalifa &Gameel, 1982). There is no efficient method to test for cotton lint stickiness; therefore, textile spinning mills may un-expectedly buy bales of sticky cotton.

Different techniques such as blending, relative humidity (Gutknecht et al., 1986), machine setting (Chellamani, 2004) and the use of spinning additives (Brushwood, 2005) can be applied to overcome the problem of sticky cotton. Nevertheless each method has its own merits and de-merits, for instance increase of relative humidity creates difficulties in the processing of cotton (Brushwood, 2005), whereas the inappropriate machine setting increase the stress on fiber, which results in fibre breakage and weaker yarn. The chemical additives are applied during ginning and spinning to control stickiness. Certain chemicals can also be applied at the gin stage to facilitate processing during spinning. Nevertheless, the use chemical additives on cotton fibre have some impact on the spun yarn quality. Fonteneau-Tamine and Gourlot (2001) concluded that the tensile properties of the ring spun yarn decrease as stickiness increases. Similarly Hequet and Abidi (2002) reported that stickiness caused by honeydew contamination has been reported to cause residues build-up on the textile machinery, which may cause subsequent irregularities or yarn breakage. These irregularities have an adverse effect on the tensile properties of the yarn.

Although there is little research on stickiness in Pakistani cottons, acute problem of stickiness is reported in the imported cottons processed by the local textile mills. In this context, the main objective of this research paper was to measure the stickiness from imported sticky cottons and to analyze the effect of stickiness-controlling chemical additives upon tensile parameters of spun yarn.

MATERIALS AND METHODS

The research work was conducted in the Departments of Fibre Technology and Chemistry, University of Agriculture, Faisalabad and Gulshan Textile Mills Ltd., Kasur. The lint samples of American ‘SJV Pima’ and Sudani 'Brakat’ cotton varieties were taken from the running stock of mills and determined for stickiness, application of different spinning additives and assessment of raw material and spun yarn characteristics.

Stickiness measurement. The samples of lint cotton were measured for stickiness according to the chemical method for cotton lint stickiness grading based on total soluble sugars concentration developed by Ali and Abdelatif (2001). The degree of stickiness can be determined according to the following ranges:

Application of spinning additives. The spinning additives were applied at 0.1 - 0.2% by weight of cotton to sticky cotton with same amount of water. Three additives at variable concentration were applied to remove the stickiness from Sudani and Pima cotton. Following variables were selected to study their effects.

Cotton Varieties:

V1 = Sudani (BARAKAT); V2 = Pima (SJV)

Neutralizer (Additives)

A1 = Flerol BW (Polyglycol Ether Fatty Acid Ethoxylates)

A2 = UPG-100 (Modified Polyglycol)

A3 = HT-60 (Ethoxy Amine)

Concentration of additives (%)

C1 = 0.50; C2 = 0.100; C3 = 0.125; C4 = 0.150; C5 = 0.175; C6 = 0.200.

Processing of sticky cotton. Spinning is an operation of making yarn from fibres by drafting and insertion of twist. All processes from blow room to roving frame are the preparatory ones for the formation of the yarn. After application of additive, the cotton samples of American Pima SJV and Sudani BARAKAT were processed through blow room, carding, drawing, roving and ring frame sections separately to make into 40s yarn. However the concentration C5 and C6 were not used for the spinning of the yarn due to poor results in fibre characteristics. Following yarn characteristics were measured.

Yarn tensile properties. Tensile properties viz., single yarn strength and yarn elongation were measured with ‘Uster Tensorapid’, which applied the constant rate of extension (CRE) principle of testing. The procedure is given in detail in ASTM Committee Standards (1997). The yarn lea-strength was determined on pendulum type tester by “Skein method” and count lea strength product value was calculated by multiplying the count value with the respective lea strength as suggested by ASTM Committee Standards (1997).

Statistical analysis. Duncan’s multiple range test was applied for comparison of individual means among various quality characters (Steel & Torrie, 1984).

RESULTS AND DISCUSSION

Stickiness level. The lowest value of stickiness was observed in American Pima cotton (V2) as 613 followed by Sudani cotton (V1) as 642, respectively (Table I). It has been reported by Perkins (1984) that if cationic additives are utilized, they will not be completely removed downstream in textile processing and will result in reduced scouring and dyeing efficiency. The individual comparison of mean values of fibre strength for different additive (A1, A2 & A3), indicate that the best value is obtained for A1 (Flerol

BW) as 613, which show non-significant difference with A2 (UPG-100) but significant difference with A3 (HT-60) with mean values 626 and 643, respectively. In a previous study Foulk and Mcalister (2002) analyzed that acid catalysis can be apply at processing stage to solve the sticky problems.

The individual comparison of mean value due to additive concentrations (C1, C2, C3, C4, C5 & C6) showed that best value is obtained for C6 as 599, which differ non-significantly with C5 as 609, but significantly differ with C1 and C2, C3 and C4 with mean values 658, 643, 631 and 623, respectively (Table I). The results are in conformity to those of Gamble (2002), who narrated that after additive application moderately contaminated cotton with an initial stickiness rating of 2 was reduced to a stickiness rating of 1, while severely contaminated cotton was reduced from 4 to 2 in stickiness rating. In a previous study Khalifa and Gameel (1982) reported that honeydew contaminated cotton in Sudan is a serious problem during processing and it can also be a problem during mechanical harvest with spindle pickers. Klein (1998) argued that cotton grows in various soils in various climates and with annually changing climatic conditions. The fibre therefore, cannot be homogeneous in their characteristics.

Yarn lea strength. The mean values of yarn lea strength at two varieties indicating highly significant difference between V1 and V2 as shown in Table II. The best value of yarn lea strength was observed in American Pima cotton as 54.89 lbs followed by Sudani ‘Barakat’ cotton as 50.52 lbs. The individual comparison of mean values of yarn lea strength for different additives (A1, A2 & A3) showed that all of values have highly significant difference with respect to one another (Table II). The best value is obtained for A1 (Flerol BW) as 53.44 lbs followed by A2 (UPG-100) and A3 (HT-60) with mean values 52.77 and 51.89 lbs, respectively. It has been reported by Gamble (2002) that when contaminated cotton is treated with (w/w) acids the rate of thermo chemical degradation of sugars is started and strength is decreased.

The individual comparison of mean value of yarn lea strength due to additive concentrations showed that all the values differ significantly from one another (Table II). The best value is obtained for C1. It was evident from the data that with an increase in additive concentration, the yarn strength was decreased. In a previous study Gohl and Vilensky (1987) reported that cotton fibre were weakened and destroyed by acids, mineral or inorganic acids being stronger than organic acids destroyed the cotton polymer more rapidly.

Single end strength. Effect of cottons varieties (V), additives (A) and additives concentration (C) for the single end strength were highly significant, while all the interactions remain non-significant (Table III). The best mean value of single end strength was observed for American Pima cotton as 207.58 g followed by Sudani ‘Barakat’ cotton as 190.94 g, respectively. Better yarn strength of V1 was due to higher fibre strength. Previously

Amjad (1999) argued that strength is a dominating factor for fibre, keeping other parameters same. It seems that 50% of the total yarn strength depended upon the fibre strength, since higher the fibre strength is related to higher yarn strength.

The individual comparison of mean values of single end strength for different additive indicated significant difference with respect to one another. The best value is obtained for A1 (Flerol BW) as 202.02 g followed by A2 (UPG-100) and A3 (HT-60) with mean values 199.47 and 196.28 g, respectively. Chellamani (2004) opined that although various methods such as maintaining the relative humidity below 50%, reducing the speed of carding and drawing machines, application of hydro-carbon plus surfactant additives are effective for processing sticky cottons, the best remains the preventive method. Individual comparison of mean values of single end strength due to additive concentrations although showed significant differences, but the best value was obtained for C1 (Table III). Therefore, increase in additive concentration decreased the yarn strength. Mauersberger (1987) argued that under some conditions even very dilute solution of common inorganic acids reduce the strength.

Yarn elongation. The individual comparison indicated significant difference between the varieties and the best value of yarn elongation was observed for American Pima cotton as 6.97% followed by Sudani BARAKAT cotton as 6.40%, respectively (Table IV). Powell (2006) reported that American SJV Pima quality is one of the best in the world” and it has been steadily improving with improved varieties and producer care in growing and harvesting the crop. The individual comparison of mean values of yarn elongation for different additives showed highly significant difference and best value was obtained for A1 (Flerol BW) as 6.78 followed by A2 (UPG-100) and A3 (HT-60) with their mean values 6.69 and 6.58%, respectively. These comparisons for additives indicated that the best value was obtained for C1 as 6.78% followed by C2, C3 and C4 with mean values 6.72, 6.65 and 6.59%, respectively. This showed that when we increase additive concentration, the yarn elongation is decreased. Mauersberger (1987) explains that under some conditions even very dilute solution of common inorganic acids reduce the strength of cotton. Yarn count lea strength product. The DMR test for the individual comparison of mean values of yarn count lea strength product (CLSP) of two varieties indicated highly significant difference (Table V) and the best value of yarn count lea strength product was observed in American Pima cotton as 2766.3 hanks followed by Sudani Barakat cotton as 2543.3 hanks, respectively. Anonymous (2005) reported that long staple Pima cotton have higher strength among other cottons. The individual comparison of mean values of yarn count lea strength product for different additive (A1, A2 & A3) showed that all of the values have highly significant difference with respect to one another. The best value is obtained for A1 (Flerol BW) as 2693.0 hanks

followed by A2 (UPG-100) and A3 (HT-60) with mean values 2657.9 and 2613.5 hanks, respectively (Tale V). Gamble (2003) indicated that cotton fiber surface chemical components including sugars, waxes and soluble metal salts affect yarn spinning through inter-fiber fractional forces.

The individual comparison of mean value of yarn count lea strength product due to additive concentrations

(C1, C2, C3 & C4) showed the best value is obtained for C1 (0. 100) as 2694.3 hanks followed by C2 (0.125), C3 (0.150) and C4 (0.175) with mean values 2668.2, 2641.7 and 2615.0 hanks, respectively. This indicated that when we increase additive concentration, the CLSP value is decreased, however measures like steam, dry heat and acid catalysis decreased the fibre quality (Foulk & Mcalister, 2002).

CONCLUSIONS

All sources of variance (the cotton varieties, spinning additives & concentrations) had significant effect of stickiness level and the tensile properties of the spun yarn. The additive A1 (Flerol BW) removed maximum stickiness and the spun yarn was also of better tensile parameters. The good yarn characteristics were found at additive concentrations the minimum (C1 to C2), because at higher concentration stickiness is removed but fibre characteristics are damaged and thus ultimate yarn tensile characteristics are deteriorated. Pima SJV yielded good results regarding fibre and yarn characteristics than Sudani Barakat after application of the spinning additives.

NISAR AHMAD JAMIL, BABAR SHAHBAZ1, MUHAMMAD QAMAR TUSIEF AND USMAN HAMEED Department of Fibre Technology, University of Agriculture Faisalabad–38040, Pakistan

Corresponding author’s e-mail: bsuaf@yahoo.com

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COTTON STICKINESS

Cotton Stickiness occurs when excessive sugars present on fibers are transferred to equipment and interfere with processing. Sugars may be insect- or plant-derived.

Though sugars are ubiquitous in lint, they usually occur at levels that pose no processing difficulties. This details the sources and components of problem sugars on harvested lint, the processing impacts of stickiness, and strategies for avoiding or mitigating stickiness.

Cottons contaminated with stickiness cause multiple problems in the spinning mills. The honeydew present on the cotton lint is able to contaminate all the mechanical instruments used in the transformation process from fiber to yarn, i.e. opening,carding, drawing, roving and spinning operations. These contaminants are mainly sugar deposits produced either by the cotton plant itself (physiological sugars) or by the feeding insects (entomological sugars), the latter being the most common source of contamination.

Honeydew, when present in sufficient quantity, is the main source of sugars that can result in sticky lint. Honeydew is excreted by certain phloem-feeding insects including such common pests of cotton as aphids and whiteflies. These insects are capable of transforming ingested sucrose into over twenty different sugars in their excreted honeydew. The major sugars in cotton insect honeydew are trehalulose, melezitose, sucrose, fructose and glucose.

Another source of stickiness is free plant sugars sometimes found in immature fibers. Cotton fiber is largely cellulose that is formed from sugars synthesized by the plant. Dry, mature cotton fibers contain little free sugar, while immature cotton fibers contain glucose, fructose, sucrose, and other sugars. If immature cotton fiber is subjected to a freeze, complex sugars may be broken down to release additional simple sugars. Less commonly, oils released by crushed seed coat fragments can also result in stickiness. In this case, raffinose is the characteristic sugar.

Sugars differ in their stickiness. For example, sucrose, melezitose, and trehalulose are all significantly stickier when deposited on fiber than are glucose or fructose. Further, trehalulose-contaminated fiber is stickier than fiber with an equivalent amount of melezitose. Mixtures of sugars, such as occur in honeydew, tend to be stickier than single sugars. Localized concentration of sugars like honeydew is at higher risk of causing stickiness than more evenly distributed sources like plant sugars.

Sticky cotton can reduce cotton gin output (in bales/hr) by up to 25%. At the textile mill, excessive wear and increased maintenance of machinery may occur even with slightly sticky cotton. In severe instances mill shutdown with a thorough cleanup is required.

COTTON APHIDS:

Aphids are slow-moving, soft-bodied insects. Adult cotton aphids are approximately 1/10 of an inch long and roughly pear shaped. They may possess wings or may be wingless. Cotton aphids have two color phases: yellowish or dark green.

The cotton aphid has two projections which arise from the upper side of the abdomen. These small tubes are called cornicles and are used to excrete defensive secretions.

Both the adult and immature stages (called nymphs) of the cotton aphid have stylet like mouthparts, which they use to suck juices from the host plant. Consequently, cotton aphids are sometimes referred to as plant lice

FIG:cotton Aphid

The cotton aphid, Aphis gossypii, excretes honeydew rich in melezitose (ca. 30–40%). Their droplets (inset, 50X) tend to be larger than those produced by whiteflies.

FIG: Whitefly

Whiteflies, Bemisia spp., also excrete honeydew, but as trehalulose-rich (ca. 40–50%) droplets (inset, 50X).

STICKINESS MEASUREMENT:

‘Stickiness’ is the physical process of contaminated lint adhering to equipment . The degree of stickiness depends on chemical identity, quantity, and distribution of the sugars, the ambient conditions during processing—especially humidity —and the machinery itself. Stickiness is therefore difficult to measure.

Nonetheless, methods for measuring sugars on fiber have been and are being developed. These measurements may be correlated with sticking of contaminated lint to moving machine parts. The physical and chemical attributes of the lint and sugars that are correlated with stickiness have been measured in many ways, each with differing efficiency and precision.

REDUCING SUGAR METHOD:

Some textile mills use reducing-sugar tests based on reduction of the cupric ion to screen for sugar contamination. These tests are relatively quick and inexpensive. However, some insect sugars are not reducing sugars, and some others are measured at different levels of efficiency by various reducing-sugar methods. Thus conventional reducing-sugar tests are best reserved for screening lint that potentially has high levels of plant sugars. In these cases and with the potassium ferricyanide (KFeCN) test, lint with reducing sugar levels below 0.3% may be processed without difficulty.

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY:

High Performance Liquid Chromatography (HPLC) identifies and measures both reducing and nonreducing sugars. The main sugars of insect honeydew, trehalulose (from whiteflies) and melezitose (from aphids), and of plant sugars (glucose, fructose & sucrose) are all readily identified in this test. The benefit of HPLC analysis is the identification of the source of contamination (whitefly, aphid, or plant) which may help identify specific mitigiation measures

MINICARD METHOD:

The physical interaction of all sugars on lint with equipment can be measured by several types of machines. The primary difficulty with these physical tests is in standardizing the stickiness measurement. As with chemical testing, these tests must be correlated with measures of fiber processing efficiency in order to interpret the results. One of these tests, the minicard, is a physical test that measures actual cotton stickiness of the card web passing between stainless steel delivery rollers of a miniature carding machine. Modeled after a production carding machine, the minicard must be run under strict tolerances. A ‘0’ minicard rating indicates that no sticking was observed, while progressively higher numbers (on a 0–3 scale) indicate progressively greater amounts of sticking during the process. Cottons with high plant sugar contents evenly distributed along the fibers may fail to be measured as sticky in this test. The minicard test is slow and has been replaced as the international standard by the manual thermodetector.

STICKY COTTON THERMODETECTOR:

The Sticky Cotton Thermodetector (SCT) measures the physical sticking points transferred to aluminum sheets by a conditioned lint sample that is squeezed and heated (to 82.5°C for 12 sec.). Levels of stickiness are categorized according to the number of specks left on the two sheets of foild.Lower numbers of specks are preferable to higher numbers; however, a specific threshold over which all cotton will result in processing problems has not been defined. The SCT takes about 5 minutes to process each sample, requires smaller initial investment costs than the minicard, is more mobile, and its results correlate well with predicted stickiness from the minicard.

HIGH SPEED STICKINESS DETECTOR:

The High Speed Stickiness Detector (H2SD) is a quicker, automatic version of the thermodetector. The cotton sample is pressed between a heated (54°C for 30 sec.) and an unheated pressure plate. Sticky points are counted and point size distribution determined by image-processing computer software. Plates are automatically cleaned between samples. The H2SD is able to analyze a sample in 30 seconds.

FIBER CONTAMINATION TESTER:

Like the thermodetector and H2SD, the Fiber Contamination Tester (FCT) measures physical sticking points (at 65% RH). The instrument feeds a thin web between two rollers. Contamination of the rollers interrupts a laser beam, resulting in a recording. Because the cleaning and recording is automated, samples may be processed as quickly as one per 45 seconds.

While there is no reliable infield method for detection of stickiness predisposition, the insects responsible for honeydew deposits can be sampled and populations measured. Not all population levels of insects lead to sticky lint; however, chronic numbers of insects, especially during boll opening or an extended season, can lead to excessive insect sugars that result in stickiness. In addition, field factors associated with risk of excessive plant sugars are lateness of the crop, fiber immaturity, and freezing temperatures before harvest.

STICKINESS CONTROL:

The most efficient way now to prevent stickiness is by managing sugar sources in the field. Detailed integrated pest management plans (see references) for both aphid and whitefly. These honeydew-producing insects may be managed by avoiding conditions leading to outbreaks, carefully sampling pest populations, and using effective insecticides when populations reach predetermined thresholds.

The risk of having excessive plant sugars can be minimized by harvesting mature seed cotton. This may be accomplished through plant management tactics that include: early and uniform planting, nitrogen management according to plant growth and yield goals, high first-position boll retention, and timely chemical termination and harvest.

If a freeze is imminent and immature bolls are present, the use of boll-opening chemicals can greatly diminish the problem of plant sugar contamination. All these measures work towards early harvest, before freezing conditions that contribute to excess plant sugars.

MITIGATING THE PROBLEM:

When field management of sugar sources is inadequate to prevent excess accumulation of sugars, mitigation tactics may be necessary to remove excess sugars from the lint. This mitigation may be achieved through both natural and managed processes; however, the specific impact of these processes on stickiness is variable and may depend on the initial level of contamination.

Natural processes include weathering, rainfall, and degradation by microorganisms. Since sugars are water soluble, rainfall will wash some honeydew from lint. If sufficient moisture is available, bacteria and molds living on the plants will decompose many honeydew sugars. Complex sugars are broken down to simpler sugars, and the simpler sugars, given sufficient time and moisture, are further broken down to carbon dioxide and water. Unfortunately, microbial action also leads to discoloration and to a weakening of the fibers as well as heating of cotton in modules that may result in reduced seed viability and problems in ginning.

Potential in-field mitigation techniques include supplemental oversprays of enzymes or water. Certain carbohydrate degrading enzymes when sprayed on sticky cotton can reduce honeydew to simpler sugars. Microbial activity on the fibers then further degrades these simpler sugars, resulting in a significant decrease in fiber stickiness. However, these enzymes require water for activity, and metering the proper amount of water for activity is a problem yet to be solved. In some areas of the world, overhead and in-canopy irrigation has been used to remove honeydew from open bolls. The frequency of this type of irrigation may be more important than the volume applied. Use of sprinklers has been limited in the Western United States, where furrow irrigation is prevalent.

If stickiness is a problem while ginning, the ginning rate of honeydew contaminated cotton can be increased by increasing the heat of the drying towers to reduce humidity. The potential for stickiness can be further reduced by lint cleaning. Both of these practices, however, can result in shorter fibers.

Conventional textile lubricants may also be used. Stickiness due to high levels of plant sugars can be reduced by storing the cotton for approximately six months.

However, storage of baled cotton will not appreciably reduce stickiness from insect sugars. At the textile mill, stickiness may be managed by blending bales and by reducing humidity during carding.

A lubricant in fog form may be introduced at the end of the hopper conveyor, and cardcrush rolls may be sprayed sparingly with a lubricant to minimize sticking.

REFERENCE:

THE ABOVE INFORMATION IS FROM THE UNIVERSITY OF ARIZONA PUBLICATION ON COTTON STICKINESS,

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