Contribution of Swelling to Water-Resistant Cotton Fabrics

Abstract

A summary of a comprehensive study of the manufacture and finishing of swellingtype water-resistant cotton fabrics of medium weight is presented. These are fabrics which stop the passage of water by the swelling of their constituent fibers. Such stoppage depends upon a zone of very high density flatwise through the fabric. Of many fabrics produced, a few were of swelling type in the grey, but only one after finishing.Variables which are usually given less consideration, had most attention, viz., maturity, and use of very immature cottons; effects of processing the yarn before weaving; and effects of increasing the tightness of fabrics by adding picks up to 36% more than normal. The fabrics were finished in a pilot plant, and an unusual study was made of the effects of successive steps in finishing on air and water resistance.Unique fabrics produced showed unusual properties, especially strength and thickness. Fabrics were evaluated for closing by methods intended to exclude water resistance from other sources than swelling. Many special tests showed that swelling capacity was reduced by finishing, to a greater extent with immature than with mature cottons. The air spaces in dense, grey fabrics of very immature cotton constitute capillary systems of unusually fine pores, especially resistant to the passage of air or water. This advantage over mature cotton is largely offset, however, because the immature cotton loses 4-5% more noncellulosic material when scoured, which leaves more space to fill by swelling. Cottons of average maturity, and from fine to average in fineness, are preferable. Entrapped air in partially swollen fabrics contributed to water resistance beyond the effect of air in ordinary water-repellent goods. This was observed especially in samples swollen in water vapor and may add to the resistance of a fabric in service if exposed to a very humid atmosphere.