Moisture Content and Moisture Regain

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.