PROCESSING STICKY COTTTON - 2
High-Performance Liquid Chromatography
on Sticky Deposits
Residues on textile equipment were collected using wet wipes . Each wipe was identified, placed into a plastic bag, and frozen. After the spinning trials, sugars were extracted from the wipes using 20 mL of 18.2- megohm water. High-performance liquid chromatography tests were performed following the same procedure used for the bale samples. Three replications were performed on each sample. The results for each sugar were expressed as a percentage of total sugars identified.
Dust was collected from 20 rotors after a 4-h run. The spinning equipment for this test was an Elitex BD200M , because it has no auto-cleaning devices to remove dust. Collected dust was frozen. We extracted the sugars from the dust using 20 mL of 18.2-megohm water. High-performance liquid chromatography tests were performed following the same procedure used for the bale samples. Three replications were performed on each sample. The results for each sugar were expressed as a percentage of total sugars identified.
The selected sugars were fructose, glucose, sucrose, trehalulose, and melezitose. Trehalulose was obtained from Cornell University; the other sugars were from Sigma Chemical Company (St. Louis, MO). The sugars first were dehydrated at room temperature under vacuum for 48 h. They were weighed immediately in tightly closed weighing containers in a controlled atmosphere (65% ± 2% relative humidity, 21degreeC ± 1degreeC. Recorded weight, m0 (dry weight), at time, t0 = 0, was used for calculation of weight-gain. Since the stickiness tests were done at 65% ± 2% relative humidity and 21degree C ± 1degreeC, the open containers containing sugar samples were stored at these conditions and weighed (weight mt) over time until the weight stabilized (14 wk). The percentage of adsorbed water on each sugar was then calculated as [(mt - m0)/m0] x 100 and plotted against time.
Differential Scanning Calorimetry
The differential scanning calorimetry technique is widely used to examine and characterize substances. The principle of this method is based on measuring the heat flux between the sample and a reference while the temperature is rising. The sample and the reference are deposited into two different pans and heated at the same rate. In this work, the reference was an empty pan. The analysis of the differential scanning calorimetry profiles indicates the thermal properties of the substances being tested; specific values such as melting point and decomposition point are obtained. The differential scanning calorimetry profiles were recorded by heating at the rate of 5degreeeC min-1 between 25degreeC and 250degreeC.
Scanning Electron Microscope
Following the processing of the 17 mixes, yarn neps were identified and collected. The samples were mounted in the stub and coated with a layer of gold by means of thermal evaporation in a vacuum coating unit. They were then examined in the scanning electron microscope using an accelerating voltage of 20 KV.
RESULTS AND DISCUSSION
Sucrose is virtually the only sugar in the phloem sap of the cotton plant . Insects produce trehalulose and melezitose by isomerization and polymerization of sucrose; neither of these sugars occurs in the cotton plant . Therefore, their presence on cotton lint demonstrates honeydew contamination. Stickiness can cause a build-up of residues on the textile machinery, which may result in irregularities or excessive yarn breakage. When cotton is very sticky, it cannot be processed through the card; however, with low to moderate stickiness levels, yarn can generally be produced. For this reason we decided to work with mixes having a very moderate level of stickiness so that residue would build-up slowly on the textile equipment. Performing the spinning test this way is more representative of industrial practice. Indeed, a spinner will not run a very, or even moderately, sticky blend. Rather, the spinner will mix the sticky cotton in such a way that no short-term effect will be noticed. Nevertheless, residues will build up over time and translate into a slow decrease in productivity and quality, forcing the spinner to increase the cleaning schedule. In this article, we present only the results of the study on the composition of residues found on the textile equipment after processing of sticky cotton blends.
The productivity and yarn quality analysis will be presented in a future article. With trehalulose content ranging from 0.003% to 0.188% and melezitose content ranging from 0.025% to 0.227% (Table 1), the 12 commercial bales selected were all contaminated with insect honeydew to some degree.
This was confirmed by the high-speed stickiness detector readings ranging from 1.9 to 69.9 sticky points. The fiber properties of the 12 contaminated bales and of the non-sticky control are presented in Table 2.
The range of fiber properties is fairly typical for upland cottons. From the 12 contaminated and the five nonsticky bales, 17 mixes were evaluated. The spinning trials were performed using the protocol outlined in Fig. 1. The high-performance liquid chromatography and high-speed stickiness detector results obtained on the card slivers are presented in Table 3.
Testing was performed on card slivers because of the intimate blend between the two bales composing the mix at this stage. As expected, sugar contents and highspeed stickiness detector readings on the mixes indicated slight to moderate stickiness.
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