Fibre sampling method
CTRL method
- CTRL Method of Sampling is also known as the Preparation of Draw-box Sliver method.
- To prepare the sample by the CTRL method, The reduced sample or lab sample is divided into 32 approximately equal parts. From each portion, a small tuft of fibres is extracted randomly.
- The same quantity of fibres is taken from each group in such a way that the total weight of the final test sample contains a weight between 200 mg and 500 mg.
- The CTRL sampling method is useful for most fibre tests like length by Balls and Baer sorters, maturity by Caustic soda method, and bundle strength by Pressley Strength Tester and Stelometer.
- In the above-mentioned test, it is convenient to prepare a representative tuft/sliver/roving out of the test sample, by cleaning it free of leaf bits and other extraneous matter, mixing various portions thoroughly, and then parallelizing the fibres.
- The test sample is finally prepared after cleaning by hand and mixing is passed through a draw-box repeatedly 5 to 10 times.
- A sample in which the proportion by the number of short, long, medium, and short fibres would be the same in the sample as in the population.
A sampling of fibres from the sliver
A sampling of fibres from the sliver is generally taken place in the spinning process.
Spinner practised this test to analyze their production process and to get an idea about yarn count and other parameters.
In fibres sampling from sliver, less precaution or awareness cause probably biased sample.
This sample has a higher chance to include longer fibre. This kind of sample creates length-biased results, therefore the Numerical sampling method (unbiased method) is preferred for this kind of sampling.
A sampling of fibres from roving
A sampling of fibres from roving are generally taking place in the spinning process. Spinner practised this test to analyze their production process and to get an idea about yarn count and other parameters.
In fibres sampling from roving, less precaution or awareness cause probably biased sample.
This sample has a higher chance to include longer fibre.
This kind of sample creates length-biased results, therefore the Numerical sampling method (unbiased method) is preferred for this kind of sampling.
If a Bias sample can able to give results of any calculations, then that kind of sample is run to some extent.
A sampling of fibres from yarn
A sampling of fibres from yarn generally takes place in spinning and weaving.
Spinner practised this test to analyze their final production and to get an idea about yarn parameters and price.
Weaver practices this test to analyze their production process to get an idea about fabric quality and estimate yarn price as raw materials.
In fibres sampling from yarn, less precaution or awareness cause probably biased sample.
This sample has a higher chance to include longer fibre.
This kind of sample creates length-biased results, therefore the Numerical sampling method (unbiased method) is preferred for this kind of sampling.
If a Bias sample can able to give results of any calculations, then that kind of sample is run to some extent.
Length-biased sample Or Tuft sample
In a length-biased sample, the percentage of fibres in any length group is proportional to the product of the length and the percentage of fibres of that length in the bulk or in the population.
To prepare a length-biased sample from sliver/roving consider the following diagram as a sliver /roving crossing.
The lines A and B in the diagram represent planes through the sliver lengthwise.
Here, the chance of a fibre crossing these lines is proportional to its length.
If therefore, the fibres crossing this area are selected in some way then the longer fibres will be preferentially selected.
This can be achieved by gripping the sample along a narrow line of contact and then combing away any loose fibres from either side of the grips.
In this way leaving a sample is prepared as below diagram which is a length-biased sample.
This type of sample is also known as a tuft sample and a similar method is used to prepare cotton fibres for length measurement by the fibrograph.
The above graph is the comparison of the numerical sample and length-biased sample with fibre length histogram and means fibre length. Here, both numerical and length-biased samples are prepared from the same materials.
The removal of a length-biased sample changes the composition of the remaining material as a higher proportion of the longer fibres are removed from it.
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| Tuft selection |
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| Lengthwise fibre sampling comparison |
In the case of equal numbers of fibres in each length group, then the total length of the fibre group with the longest fibres will be always greater than that of the other fibre length groups. As a result, it shows that there will be a greater number of that length fibres in the taken sample.
By a similar line of reasoning if the sample is cut at planes A and B the section between the planes will contain more pieces of the longer fibres because those fibres are most probably cross that section.
The use of a length-biased sample is deliberate in this case so that the measured mean fibre diameter is then that of the total fibre length of the whole sample.
If all the fibres in the sample are considered as being joined end to end the mean fibre diameter is then the average thickness of that fibre.
Questions -
- What is the CTRL method?
- How sampling of fibre from the sliver is done?
- How sampling of fibre from roving is done?
- How sampling of fibre from yarn is done?
- What is length biased sample or tuft sample?
References
Cenote, M. (2015). Google Books. In The SAGE Guide to Key Issues in Mass Media Ethics and Law (pp. 847–858). SAGE Publications, Inc.
Fundamental textile testing: Mechanical and Physical Tests. (n.d.). Fundamental Textile Testing: Mechanical and Physical Tests. from https://www.eurofins.com/textile-leather/articles/fundamental-textile-testing-mechanical-and-physical-tests/
Handbook of textile testing and quality control - Google search. (n.d.). G.Co. from https://g.co/kgs/RvVMgm
NPTEL IIT. (n.d.). Note.Ac.In. from https://nptel.ac.in/courses/116102029
Elsevier. (2016). Performance testing of textiles (1st ed.). Woodhead Publishing.
Houck, M. M. (2009). Identification of Textile Fibers (M. M. Houck, Ed.; 1st ed.). Woodhead Publishing.
Textile School. (2010, October 27). Fibre Identification - tests to identify a fibre. Textile School. https://www.textileschool.com/321/fiber-identification-tests-to-identify-a-fibre/
Trivedi, Y. (2020, April 10). Identification of Textile Fibers. Textilesphere.com. https://www.textilesphere.com/2020/04/identification-of-textile-fibers.html
(N.d.). Textilelearner.net. from https://textilelearner.net/classification
Further reading -
(Part-1) Fibre sampling method for testing - Zoning method
(Part-2) Fibre sampling method - Numerical, Random and cut square method
(Part-3) Fibre sampling method- CTRL, for Sliver and roving, from yarn
Writer - DSPAT Team
