Moisture Content and Moisture Regain
What is Humidity?
Humidity is a term used to describe the amount of moisture present in the atmosphere. This can be described in terms of Absolute Humidity or Relative Humidity.
Absolute Humidity:
It is the weight of water present in a unit volume of moist air. It can be expressed interns of gram per cubic meter.
Relative Humidity:
It is the ratio of the actual vaper pressure to the saturated vapour pressure at the same temperature.
RH% = Actual vapour pressure / Saturated vapour pressure x 100
Moisture Content (M) = Weight of Water / Total weight of material x 100
Moisture Regain(R):
It is defined as the weight of water in a material expressed a percentage of the oven dry weight of the material.
Moisture Regain (R) = Weight of Water / Oven dry weight of the material x 100
The temperature of the oven dryer should be 105* ± 3*c. The water partile should be removed and time is 2 hours.
For Example:
Initial weight of sample = 10grms.
Over dry weight of sample = 7 grms.
Weight of water= 3 grms.
Moisture content % = 3/10 x 100
Moisture Regain % = 3/7 x 100
What is standard testing atmosphere?
It is an atmosphere with a relative humidity of 65 ± 2% and at temperature of 20*c ± 2*c (68* ± 4*F).
But in India, temperature of 20*c is difficult to obtain, and so a higher standard temperature of 27*c ± 2*c (81* ± 4*F) is used.
Standard Regain:
Raw cotton- 8.5%
Cotton yarn- 7 to 7.5%
Silk- 11%
Wool- 17%
Viscous- 13%
Nylon- 4%
Polyester-0.4%
It is the one which is adopted for business purpose and it is generally very close to the standard Regain.