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Good plant moisture status is critical in the first 20 days after flowering to allow potential fibre elongation rates.
The linking farming systems initiative implemented by CSIRO, CRDC and the cotton CRC, is working to make more cohesive linkages between farming systems research and textile research. This is being realised by undertaking studies designed to comprehensively understand how on-farm practices, variety selection, and post harvest processing directly influence textile performance.
As part of this work, CSIRO Textile and Fibre Technology (CTFT) is employing its cotton mill, fibre quality and textile research capability. CTFT has a full-scale cotton spinning mill which is used to process large amounts (greater than 50kg) of lint. This system is well used and has been employed to assess new CSIRO cotton varieties
from full-scale production trials.
The linking farming systems project has identified a need to test the textile performance of batches of cotton from field trials that are too small for processing via CTFT’s full-scale mill. To meet this need, CTFT has recently re-furbished a ‘Shirley’ miniature spinning plant.
This equipment was first manufactured in the mid 1950s by the Shirley Institute in England and was originally designed for and employed by commercial mills and research organisations for processing small batches (less than one kg) of fibre to determine spinability. With the advent of high volume instruments (HVI), such practices were made redundant and so the production of such small-scale spinning apparatus was discontinued by the 1980s.
HVI has revolutionised the measurement of cotton fibre quality, and gives good information on fundamental fibre quality parameters such as fibre length and strength. But HVI alone will not give a complete picture of the textile performance attributes of a particular cotton such as processing performance, fabric strength and dye uptake.
The linking farming systems project is undertaking field research aimed to understand and manipulate important fibre quality parameters, such as micronaire, fineness and maturity. Such field experiments are typically well designed and replicated, with numerous samples being generated. The only practical way of fully assessing the textile performance potential of these samples is to employ a miniature spinning protocol.
The majority of Australian cotton is spun into ring spun yarns. The standard steps in a full-scale commercial ring-spinning process involve:
1. Opening and cleaning
This is when a bale is opened and exposed to conditioned air in the mill. The lint is then subjected to a series of rollers and beaters in the ‘blow room’ to remove trash and open the fibre.
2. Carding
this removes considerable amounts of short fibre, neps and trash, and aligns the fibre which allows a sliver to be formed.
3. Drawing
Drawing is the process of teasing out the sliver to reduce the number of fibres in the cross section which then reduces the sliver’s weight. Two draw passages are normal, which also facilitates blending and further fibre alignment.
4. Roving
This process further draws out the sliver and for the first time twist is added.
5. Spinning
The roving is then subjected to spinning, which further draws out the fibres and adds more twist. Most Australian cotton is ring spun into 15 to 30 tex yarns. Tex is a unit
of linear density or weight per unit length of yarn. One thousand metres of a 20 tex yarn weighs 20 grams.
The Shirley miniature spinning plant consists of a small card, draw-frame and ring spinning frame. Since no opening or pre-card cleaning is possible on the miniature system, the manufacturer’s recommendation are to card the material twice. Following carding, three miniature draw passages are recommended to draw out the sliver until it is light enough to be spun directly on the miniature spinner. Unlike full-scale spinning, this miniature system does not include the crucial intermediate step of producing a twisted roving between drawing and ring-spinning.
CTFT found that inferior and practically un-processable yarns were produced when using the recommended miniature system. Numerous breaks occurred during processing, with slubbing (thick places)-prone weak yarns being produced. This occurred because of the large amounts of draft and twist that were applied to the un-twisted sliver on the ring-spinning machine.
An alternate miniature spinning protocol was devised using a combination of both miniature and full-scale equipment, while still maintaining the small sample size. The main difference between the traditional and alternate miniature spinning protocol, is that the alternate process has an additional step of creating a twisted roving between drawing and spinning, and only relies on two draw frame passages.
In addition, full-scale machinery is used for the second draw passage, the creation of twisted roving and ring spinning, which is more in-line with a commercial spinning situation. The experimental sample required for this protocol is small — only 170g.
To facilitate a comparison between the two spinning methods, 20 tex yarns were manufactured using the industry standard Sicot 71BR variety. There was no significant difference between commercial full-scale and the new alternate miniature spinning system for processing performance, and yarn evenness and strength (Figure 2).
The miniature spinning protocol has already been put to good use, with small samples from defoliation timing experiments being spun, knitted and dyed. The results of this work will be reported in another Cottongrower article, and will also be presented at the up-coming Australian Cotton Conference in August 2008.
Much thanks goes to Martin Prins for his advice on operating the miniature spinning plant and to Fred Horne and Mark Freijah for assisting in processing. We thank the CRDC, the Cotton CRC and Cotton Seed Distributors for financial support via the ‘Linking farming systems to fibre quality and textile performance’ project. For more information about this work please contact Dr Robert Long
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