Around 50% of the cotton bales produced in the world are sold based on the analysis of their technological characteristics using a standardized instrument for testing cotton (SITC). In the United States of America, periodical studies of variability of the results allow the results to be accompanied by commercial tolerances to limit the frequency of claims. However, to our knowledge, no such study has been conducted in Africa. For this reason, we studied within-bale variability of fiber micronaire, length, uniformity, strength, reflectance and yellowness as measured by the SITC. We took eight samples per bale from 215 cotton bales produced by 27 ginning mills in eight Sub-Saharan countries in Africa in two cropping seasons. Our representative sample was composed of 1720 fiber samples that were analyzed in controlled conditions using the SITC in a laboratory in which international recommendations are fully respected. We measured within-bale variability and suggest a sampling method and procedure to perform technological and instrumental tests in West and Central Africa.
The friction and cohesion forces take an important place in fiber processing. The friction force defines the sliver and rover strength and, up to a certain level, the yarn strength also. Many works deal with the measuring of the inter-fiber friction force using different methods. Some of these studies concern the measure of the frictional force on one single fiber. Basu et al.[1] measured the variation in the frictional forces developed between a straight-edge probe and a single Egyptian cotton fiber under a range of some normal loads. Postle and Ingham [2] measured the frictional force during the withdrawing of a wool fiber from a compressed pad. Lindberg and Gralen [3] measured the frictional force between two fibers twisted together. Lord [4] studied the frictional force developed during the relative motion of two identical fiber fringes. The method of El Mogahzy and Gupta and El Mogahzy and Broughton [5,6] is very similar to Lord's, but their apparatus was more precise. They studied theoretically the friction phenomena and tried to explain Howell's equation.The friction may be approached by the drafting force. Martindale [7], Kamarov et al. [8] and Cavaney and Foster [9] tried to measure the drafting force for cotton and rayon. They showed its dependence on the draft, the input sliver count, the compactness, the sliver direction, the distance between the drafting cylinders (ratch), the front roller speed and the fiber length. Oslen [10] later used the device of Martindale, performing the measurement precision by using an electric force sensor. Brook and Hannah [11] measured the force developed during the extension of twisted wool roving at the same magnitude speed as the normal drafting. Grishin [12] and Hannah [13] tried to explain theoretically the drafting force. There are some other methods for measuring inter-fiber frictional behavior, as in the method of Baratlett et al. [14]. They studied the behavior of yarn withdrawn at a constant speed and tension, in contact with a short portion of a music wire, a yarn or other flexible objects. 1 There are few methods for measuring frictional forces in yarn. King [15] and Morrow [16] measured frictional Abstract The friction and cohesion forces are some of the most important parameters that affect the yarn spinnability and tenacity. A new and simple device was carried out in order to quantify the friction and cohesion forces during a quasi-static fiber slippage in a sliver. This device was composed of two identical small carriages. One of them was fixed, whereas the second was moving on a linear guide. A piece of sliver was put down in the carriage channel in zero-gage position. The sliver was compressed with the upper carriage sides, where two identical weights were loaded. This apparatus was tested under different loads, sliver counts and speeds. The results were analyzed in order to check out the parameters which characterized the friction force during inter-fiber slippage.
Six types of 30 tex silk and cotton blended yarns at 50/50 blending ratio were spun in the cotton spinning system in order to study the effects of blending factors on the fiber distribution in the yarn cross-section. The blending factors studied here were the blending methods, intimate and drawframe blending, and the silk waste types, inferior knubbs, filature gum waste and pierced cocoon. A new method of zoning the yarn cross-section has been proposed in order to analyze the fiber migration. Three migration parameters, the Index of Blend Irregularity, the Migration Intensity and the Migration Index were studied in the present work. The intimate blending gave a more homogeneous fiber distribution, with no radial migration tendency. The coarser silk fibers and more irregular in length provided blends that presented non-random heterogeneity. Generally, the silk fibers slightly tended to migrate toward the yarn core.
Currently, textile industrialists have to consider the sensory aspect in their design and manufacturing specifications. To describe the sensory quality of products, sensory evaluation does exist and is widely used in the food and cosmetics areas. These methodologies have been successfully transposed to tactile evaluation of textile fabrics for different textile materials: plain weave fabrics with different post‐treatments and non‐woven are used for medical gowns and drapes. In our study, we have asked our trained panel composed of nine assessors to score a list of already defined sensory attributes for different knitted fabrics made of silk/cotton blends. The spinning parameters which have been changed are the type of silk fibre (three types), blending techniques – intimate and draw frame blending – and the silk content. All these parameters can more or less influence the tactile perception of the final knitted fabric. In this paper, the results of our analysis are presented and discussed in order to answer questions such as: “Are these two fabrics different?”, “What kind of difference is there?” or “What are the sensory characteristics of these fabrics?”. The concrete steps of the evaluation will be presented and specifically the training and performance analysis of the panellists who were obliged to adapt their evaluation procedures to small knitted samples. The protocols used to carry out fabrics description and comparisons when all assessors cannot evaluate all the products under study will also be detailed.
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