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Measurement of regain - oven dry method, IR drying method, Capacitance/Resistance method

Measurement of textile material moisture

By oven-dry method

  • In this method, the Sample is dry in a specific conditioning oven. The use of the conditioning oven to dry a sample is the correct standard procedure.
  • The oven is large so that it contains the fibre sample in a mesh container. 
  • The container chamber is hung from inside the oven by one pan of the balance, while the mechanism is outside of the chamber.
  • This indicates that the weight of the sample can be monitored without disturbing the outer system. 
Oven dryer instrument
Oven dryer for textile testing purposes
  • A continual flow of air at the correct relative humidity is passed through the oven which is maintained at 105° C.
  • The main advantage of using a conditioning oven for carrying our regain determinations is that all the weighing is carried out inside the oven. 
  • The method is based on the assumption that the air drawn into the oven is at the standard atmospheric condition. 
  • If this is not the case the correction has to be made in Percentage correction.
  • Correction in % = 0.5 ( 16.48 x 10∧4 x Ex R) % 
  • Where R = relative humidity % / 100, and E= Saturation vapour pressure in pascals at the temperature of the air entering the oven (taken from a table of values)



IR drying method

  • IR drying method is modern and useful to quickly dry the sample.
  • With the help of the IR drying method, samples can be easily dry by an IR lamp.
IR drying principle
IR drying principle
  • A balance is used to measure the weight of the specimen parallel to the IR drying method.
  • In this method 5 grams of cotton specimen dry in 8 min and viscose specimen dry in 3 min.
  • The accuracy claimed is that the results are reproducible to within 0.2 per cent with unskilled operators.
  • This makes the maturity test faster. While in another method 1-2 days are required for drying the sample.



Capacitance/Resistance method (Indirect)

  • The electrical properties of fibres change quite markedly with their moisture content so that the measurement of resistance or capacitance changes can be used to give an indirect method of regaining determination.
  • In a typical electrical resistance measuring instrument, two electrodes are pushed into a package of yarn, and the resistance between the electrodes is measured by suitable electronics, the answer is displayed on a scale that is directly calibrated in regain values. 
  • Different electrode sets are used for different packages.
  • I.e. - long thick prongs used for bales and short needle-like probes used for yarn packages.
  • The instrument has to be calibrated for the type of probe, the type of fibre, and the expected regain range. 
Moisture regain measurement by capacitance method
Electrode for measuring moisture regain
  • The great advantages that electrical methods possess over-drying and weighing methods are the speed and ease of reading, the fact that they can calibrate directly in regaining units and it can be made portable. 
  • The disadvantages of electrical methods are the need to recalibrate them as they are indirect methods, the variations in readings due to packaging density, the presence of dyes, and antistatic agents, and also variations in fibre quality.
Questions -
  1. How oven-dry method works?
  2. How IR drying method works?
  3. How capacitance/resistance method works?

References

Atmospheric humidity and the moisture content and regain of textile materials. (1940). Journal of the Textile Institute Proceedings, 31(1), S3–S4. https://doi.org/10.1080/19447014008687574

Babu, S. (n.d.). Testing of moisture regains and moisture content of cotton fibres. Textileadvisor.com.from https://www.textileadvisor.com/2021/07/testing-of-moisture-regain-and-moisture.html

Cenite, 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

Hasan, M. (2014, December 22). Relation between moisture regain and Moisture Content. Textile Calculations. https://www.textilecalculations.com/relation-between-moisture-regain-and-moisture-content/

NPTEL IITm. (n.d.). Nptel.Ac.In. from https://nptel.ac.in/courses/116102029

Trivedi, Y. (2020, April 11). Moisture Relation in Textiles. Textilesphere.com. https://www.textilesphere.com/2020/04/moisture-relation-during-testing.html

What is moisture content and moisture regain? (2020, August 12). Texpedi: A Reliable Source of Learning Textiles; //www.texpedi.com/. https://www.texpedi.com/2020/08/moisture-content-and-regain.html



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