The Relationship of the Geometry of Plain Knit Cotton Fabric to Its Dimensional Change and Elastic Properties

Abstract

A study was made of the geometry of 34 different plain knit cotton fabrics which were knit, in a wide range of stiffness, of six different yarns (12/1, 20/1, 28/1, 36/1, 40/1, 50/1). Stitch length in terms of course and wale spacings and diameter of yarn ranged from l = 2 p + w + 4.34 d to l = 2 p + w + 6.37 d, as compared with the theoretical value of l = 2 p + w + 5.94 d which Peirce derived. Both the gray and the finished fabrics exhibited distortion. Laundering with screen- or tumbler-drying brought about rearrangement in the structure so that the data for wale and course spacings of the laundered fabrics followed the parabolic curve p2 = a ( w + b) . When fabrics were given a relaxation treatment to remove distortion, the data of wale and course spacings both before and after laundering also followed a parabolic curve. For the relaxed fabrics, dimensional changes in length and width in laundering were not excessive and did not vary with cover factor (stitch length/diameter of yarn). The elastic properties changed greatly with cover factor for the unlaundered, relaxed, and laundered fabrics. As cover factor increased, the strain increased linearly when the fabrics were not distorted. Cover factor varied linearly with recovery and permanent set, with delayed re covery and permanent set increasing and immediate elastic recovery decreasing. Poisson's ratio increased somewhat with cover factor when the fabrics were not distorted.