Factors Affecting the Moisture Regain of Textile Materials

Factors Affecting the Moisture Regain of Textile Materials
Rana Sohel
B.Sc. in Wet Processing
Noakhali Textile Engineering College
Facebook: http://www.facebook.com/rana.sohel.5

Moisture Regain:
Moisture regain of a textile fiber is defined as: The equilibrium weight of water contained by a specimen expressed as a percentage of its oven-dry weight. That is,

R=100(Ws-Wd)/Wd %

Factors Affecting the Regain of Textile Fiber:
Different fiber types absorb different amounts of moisture depending on their affinity for water as shown in Fig.

There are different factors that effect the moisture regain of the textile materials, such as;
  1. Relative Humidity
  2. Time
  3. Temperature
  4. The Previous History of The Sample
Relative Humidity:
Relative humidity is the most important factor that affects the regain of textile materials. The higher the relative humidity of the atmosphere, the higher is the regain of textile material which is exposed to it. If the relative humidity in the air is more then there will be more moisture regain or more rate of conditioning of textile materials and vice versa.   
Material that is in equilibrium at a particular relative humidity which is then moved to an atmosphere with a different relative humidity takes a certain amount of time to reach a new equilibrium. The time taken depends on the physical form of the material and how easily the moisture can reach or escape from the individual fibres. For example the British Standard for count testing suggests a period of one hour for yarn in hank form to reach equilibrium, but three hours for yarn on packages.

A material placed in a given atmosphere takes a certain time to reach equilibrium. The rate of conditioning depends on several factors, such as;
  • The size and form of sample
  • The type of material
  • External conditions
The effect of temperature on regain is not important. A change of 10 0C will give a change in regain of cotton of about 0.3 percent. This effect can be ignored. Now we can say that for practical purposes the temperature does not affect the regain of a sample.

The previous history of the sample:
The previous history of the sample can affect the equilibrium regain of the sample. The hysteresis is a good example. Processing can also change the regain. When oils, waxes and other impurities are removed then regain may change.  
From the below fig we can learn,
Different moisture content depending on whether it was previously wet or dry. Processing of the material can also change its regain value by altering its ability to absorb moisture. The removal of oils, waxes and other impurities can also change the regain by removing a barrier on the fibre surface to the flow of moisture vapour. For example the standard regain value for scoured wool is 16% and that for oil combed tops is 19%.
A plot of regain versus relative humidity for viscose fibers
A plot of regain versus relative humidity for viscose fibers
A comparison of the moisture uptake of fibers
A comparison of the moisture uptake of fibers


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