The relationship between the loop length and properties of some plain weft-knitted fabrics
The object of this work is to investigate the effect of loop length on the geometrical and more particularly on the physical and mechanical properties of the plain weft knitted fabrics. Two sets of fabrics were produced from 2/26s worsted yarn using knitting machines different in type and gauge. The first set was knitted from single yarn and the second from two-ends with a wide range of loop length. Both sets were given three different relaxation treatments, dry, wet- and full-relaxation. Dimensional measurements and geometrical parameters were determined and examined and the results show that for some fabrics there is some deviation from the results of other workers in this field. The study also involved measurements and tests of certain yarn properties which provided useful background information about this yarn and which might help to explain certain properties of the knitted fabrics. The yarn properties measured and tested were, twist, friction, flexural rigidity, tensile and elastic properties. Experimental results indicate that an increase in loop length leads to an increase in air permeability and percentage weight loss when the fabric subjected to abrasion. It is found that for two-end fabrics the percentage weight loss is non-linearly related to the loop length and this reflects the yarn arrangement within the structural unit cell. While there is not always a direct relation between the loop length and the fabric thickness, there is however, a proportional relationship between the parameter t/L and the cover factor K. In this investigation, the predicted tensile strength and extension at the point of break worked out on the geometrical basis when the fabric is extended in walewise and coursewise direction. Once more the fabric made from two-ends behaved differently when it was subjected to tensile and to repeated cycles of extension. Fabrics made from two-ends are stronger at break but have lower recovery than the fabrics made from single yarn. While there is a relationship between the total elastic recovery and the loop length for the fabric made from one-end, it appeared that it is difficult to find a systematic relationship between the total elastic recovery and the loop length for fabrics made from two-ends in both the dry- and fully-relaxed state due to the involvement of the yarn arrangement within the structural unit cell of the fabric. In addition to the pattern of yarn arrangement within the structural unit cell in the two-end fabric, there is relative yarn movement which may affect the dimensions of the cell.