MOISTURE RELATIONS OF TEXTILE FIBRES

The hygroscopic nature of textile fibres, their ability of absorb and desorb water is of great importance. It is important when fibres undergo spinning of yarns and manufacture of fabrics, dyeing and laundering. All the native fibres contain certain chemical groups of polar character i.e. they possess an attraction for water and for other polar chemical groups such as hydroxyl (OH), carbonyl (CO), carboxyl (COOH), amino (NH₂), amido (CONH₂) and imino (NH). It is the mutual attraction of these polar groups which provides the secondary forces which hold the molecular chains together and maintain the micellar character of the chain-bundles. As these groups also attract water, it is possible for this compound to enter between the molecular chains and push them apart, therefore, water is an excellent plasticizer for the native and regenerated fibres.

Moisture content is important in textile fibre. Moisture content is the amount of moisture expressed as a percentage of the total weight but moisture regain is calculated as a percentage of the over-day weight (constant weight) at 105-110^oC. These vary with the humidity and temperature. Adsorption in its strict sense is a purely surface phenomenon, and absorption is used to indicate the internal effect; the word ‘sorption’ may be used in a general sense to cover both terms.

Moisture content of cellulose is determined by the accessibility of the hydroxyl groups and is increased when more OH groups become accessible, but blocking of OH groups by other groups decrease the moisture sorption of the material. Polar groups attract the moisture. Accessibility of polar groups determines the amount of water absorbed. Strong or weak H-bonds determine the separation of molecular chains and admit more water.