Abstract
The chang of bulkiness, specific volnme, of crimped synthetic yarns by elongation was studied. The specific volume of yarns was determined by the cross sectional area of yarn, which was obtained by the maximum radius of crimped yarn.
The results are as follows;
Elongation reduces the cross-sectional area of yarn. The yarn prepared by the conventional twist method has more variation on the curve of reduction of the area compared with these prepared by the false or stuffer-box method.
The circle having an area equal to cross-sectional area of yarn is termed mean circle. The displacement of center of mean circle occurs during elongation. The displacement consists of radial and angular motion, which relates each other intimately. The elongation which causes a large angular displacement is also accompanied by a large radial displacement. Both displacements have no direct effect on bulkiness, but the have some effects on a change of cross-sectional area of crimped yarn.
The total volume of crimped yarn was obtained by summing up the volume of each section under stretching. There is the maximum specific volume between 56-60% elongation in the conventional and false-twist method yarns, but in the stuffer-box method yarn it decreases rapidly with elongation and then approaches the constant value.
