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Can We Modify the General Equation to Estimate CS Of Combed Yarns? |
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Combing brings about the following changes in fibre properties: |
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A Reduction in %-age fibres shorter than 12-mm; |
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An increase in %-age fibres longer than 24-mm, as a result of the truncation of the length distribution by removal of short fibres; |
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A very marginal increase in Baer sorter effective length, which may be missed in testing; |
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A marginal increase in fibre millitex as a result of the removal of the short fibres which are also generally immature and hence fine. |
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The first three beneficial contributions of combing will result in a reduction of the irregularity of the combed yarn, and therefore, in an increase in the CS of the combed yarn. |
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Combing also endows the sliver with two other advantages: an improvement in the alignment of fibres within the sliver; a reduction in the number of hooked fibres in the sliver, and in the extent of hooks. These additional beneficial contributions of combing will also result in a reduction of yarn irregularity, and therefore, in a further increase in yarn CS. |
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We now recall another beneficial contribution of combing that has been pointed out by Lord (7) “……. it is hardly surprising to find that, for carded yarns, the bundle strength measured at zero test length provides information less useful than measurements at 1/8-in. The increased regularity and parallelization of fibre arrangements in combed yarns suggests a decrease in effective length of yarn element –that breaks in yarn tenacity testing -- a feature which may also occur in doubling when fibres are brought into more intimate contact with each other. For such material the best test length for fibre-bundle strength determination may be one closer to zero than that found suitable for the looser, carded yarns.” In other words, combed yarns gain in strength over carded yarns by a shortening of the gauge-length of fibre breakage in yarn testing. |
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One method of using The General Equation to estimate combed yarn CSP comes to mind. This is to test the combed sliver for fibre characteristics, and then substitute these values in The General Equation for carded yarns. This method, however, will take into account only one aspect of the contribution of combing towards the increase in yarn CSP. We will still have to modify the equation to take account of the effects of improved fibre parallelization, reduction in fibre-hooks, and any reduction in the length of the yarn-element that breaks in tenacity test of yarn, as postulated by Lord. Preliminary attempts showed that this could possibly be successful. |
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In other words the compounded fibre parameters that we constructed for estimating the fibre-slippage fraction and the irregularity fraction stand extrapolation for combed sliver. |
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