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STUDY ON BARRE CAUSED BY RAWMATERIAL - Page 2

FIG:2

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The AFIS Maturity module is a single fiber measurement of individual fiber maturity. The individual fiber maturity information gives a distribution of fiber maturity as well as the average fiber maturity. The distribution enables us to identify the very immature fibers and it is described by the Immature Fiber Content (IFC%). Figure 2 clearly shows a considerable difference of the three bales in the IFC%. Maturity differences in cotton can also cause defects in fabric such as white speck neps. Fabric in figure 3 was knitted from yarn produced from three different cottons having similar micronaire values. There was a significant difference in the amount of white specks in the three fabric samples. The three cottons were tested on the AFIS Maturity module and the results are given in figure 4. The differences in the AFIS IFC% correlates visually to the amount of white specks in the three fabrics. Interesting is that the overall average maturity ratio from  the three cottons was very similar, giving no indication of a potential problem of white specks.

FIG 3:

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FIG 4:

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Variation of Maturity in Sliver

There is a possibility to optimize the carding process to make sure all cards remove as much of the immature fiber as possible. Figure 5 shows the results from testing a line of cards all fed from the same bale laydown. It is interesting that while the card mats all show very similar results the card slivers show quite some variation. The possibility of the influence of carding on the maturity of the sliver was investigated further using the AFIS Maturity module. Several individual cards were analyzed and it was apparent that there was a large variation in the amount of immature fibers removed by the cards. This initial trial indicated that it is possible to change the mechanical setup of a card to influence the removal of immature cotton fibers. These results are shown in figure 6.

FIG 5:

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FIG 6:

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Fluorescence

Another major cause of fabric barre’ is a change in the cotton fiber fluorescence. Fluorescence can be measured by the Uster Fiberglow, which measures the ultraviolet light that is reflected from the cotton sample. Fluorescence (UV) is not cotton color, but the effect of sunlight on the structure of the fibers.

Fluorescence can cause BARRE if

  • the variation in average UV readings between mixings is high

  • C.V.% in UV readings within a mix is high

  • End of season cotton crop changes

  • Outside storage of cotton bales   is practiced

  • mixing high and low UV bales is done

  • UV readings increase over time in the  warehose

Bale laydowns should be controlled using similar techniques that are used for micronaire. These solutions for controlling fluorescence are given below

  • UV  test every bale before making mix

  • dont allow more than 10 points difference of UV readings within mix

  • UV average should be less than 1 point between mixes

  • category groups should be set up for UV

The variation within a single mix should be a maximum of +/- 5 points. The average UV reading of the mix should not change more than +/- 1 point from mix to mix. There is normal change in the UV readings from crop year to crop year. This is due to seasonal changes as well as the difference in UV from cotton stored in a warehouse from 9-12 months. Blending old crop and new crop must be done carefully to reduce the chance of creating fabric barre’. Typically each new year the cotton crop will have a different UV average and range depending on the weather at the time of the harvest.

Conclusions

At least 70% of the causes of fabric barre’ are due to variations in fiber properties. There are specific solutions available for spinning mills to control the key fiber properties that affect the dyeing and finishing of cotton fabrics. Individual bale measurements of micronaire, maturity and fluorescence will help the spinning mill to control all aspects of fiber barre’ problems. The exact solution will depend greatly on the specifics of end product, spinning system and raw materials used by individual mills. Application guidelines are available for use in selecting bales for mixes and storing bales in the warehouse. Instruments and software programs are available to help the spinning mill monitor and control these specific fiber properties.

REFERENCE:USTER APPLIACTION HANDBOOK FOR AFIS PRO

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