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.
It is the weight of water present in a unit volume of moist air. It can be expressed interns of gram per cubic meter.
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
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.
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.
Raw cotton- 8.5%
Cotton yarn- 7 to 7.5%
It is the one which is adopted for business purpose and it is generally very close to the standard Regain.