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EFFECT OF COTTON FIBER LENGTH DITSTRIBUTION ON YARN QUALITY - 2

cotton yarn

During the past few years, thousands of cotton samples have been analyzed at the ITC using the AFIS. Results for most of the cottons indicate a very small percentage of fibers in the length categories of 2 inches and longer. We can postulate either that those very long fibers really exist or that the AFIS over- estimates the length of the longest fibers. To investigate this, 14 USDA standard cottons were tested on the AFIS, Sutter Web Fiber Array and Peyer AL 101. Results showed that the instruments correlate very well for the shortest fiber percentages (Figures 2 and 3), although the levels are different.

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For the very short-staple cotton (staple 26), the length distributions obtained are very similar (Figure 4).

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For the short-staple cotton (staple 32), AFIS and Peyer are in good agreement, but the Array method tends to get higher percentages for the longest fibers (Figure 5).

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For the medium (staple 35) and long (staple 40) fibers, the discrepancy between instruments is clear (Figures 6 and 7).
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Neither the Peyer nor the Array showed any fibers to the longer than 2 inches, but the AFIS did indicate some of these for most of the samples. This suggests that the AFIS tends to over- estimate the length of the longest fibers. One hypothesis to explain this result is that the speed of the fibers passing trough the sensing device is not constant; i.e., the longer the fiber, the higher the friction forces for the air-to-fiber interface. This could lower the speed, resulting in a longer electronic signal.  Given this anomalous result with the AFIS, the question arises whether it is a useless artifact or if it has predictive power.

This led to the second experiment involving 18 upland varieties grown in 3 locations with 2 field replications per location. Using the AFIS multidata, for each length category, defined, an analysis of variance was done. Figures 8, 9 and 10 give the variety and location effects for the three length categories. For the length category [0.25; 0.50], the variety effect is highly significant, but the location effect and the interaction effect × are not statistically significant. For the length category [1.25; 1.50] both the variety and the location effects are highly significant, but the interaction effect location*variety is not. For the fibers longer than 2 inches, the variety effect is highly significant, the location effect significant and the interaction effect location*variety non- significant.

These results suggest at least two very important things. First the length distribution by weight is variety related; this implies that breeders could modify the length distribution. Second, the longest fibers measured with the AFIS, although a very small percentage of total fibers, are also variety related. This means that the fibers measured as too long by the AFIS cannot be dismissed as meaningless.

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To investigate further, we calculated the coefficients of correlation between major yarn characteristics and the percentages of fibers in the different length categories. For  Count Strength Product (CSP), these correlations are quite similar for all the types of yarns.ring or rotor, carded or combed (Figure 11).

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