Last updated on August 6th, 2023 at 12:56 am
Treating fabrics to withstand water. Proofing against water.
The acts of making fabrics impervious to water with use of substances like rubber etc. Methods of impregnating or coating fabrics with substances like oil, wax, rubber, resin etc.
Fabric where in the pores, the open spaces between warp and weft yarns and also between fibrs are filed with appropriate substances and which results in having a continuous surface of the fabric and with very little air-permeability.
Fabric where in fibres are usually coated with a hydrophobic substance and whose pores are not filled in the course of the treatment. These are therefore quite permeable to air and water vapor.
Natural fibres are hydrophilic and can absorb water and therefore are not water repellent; the same is the case with regenerated fibres like rayons etc., or even protein fibres. And so these can’t be used as wet-weather-wear, if external water-repellent finishes are not given.
Synthetic fibres, on the other hand, are hydrophobic and have lower or nil water absorbency or water absorbing capacity. The fabrics of these fibres have the inherent capacity to withstand wet-weather-wear and these need no treatments.
This factor achieved considerable importance in World War-2, when a serious consideration had to be given to this factor and tests were made which showed quite interesting results. As a result of this wool as outer great coat in the Army uniform was given up and was substituted by light weight cotton fabric with a water-repellent finish.
The unique ability of cotton fabrics, swelling under water and thereby closing the interstices, results in making the garment water-repellent, after initial wetting and yet this cloth remains air-permeable, when dry.
The Shirley Institute undertook this experiment, which ultimately resulted in the development of ‘Shirley-cloth’ of soft yarns with high thread count, in Oxford weave.
Difference Between Water Proof and Water Repellent Fabric
|Air-permeability||Small or nil||Large|
|Water vapor permeability||Small or not||Large|
|Characteristics||Resistant to passage of water even under hydrostatic head||Resistant to water and rain and spreading of water but permits water under hydrostatic head|