1. Characteristics of elastic denim
The main component of elastic denim is elastic silk. The elastic filament is a combination of polyurethane polymers. It can stretch five to six times after being pulled, and can return to its original state after the potential force is small. Even if it is repeated many times, the elasticity will not disappear. Elastic denim can be divided into weft elastic, warp elastic and warp weft elastic, and the most commonly used is micro elastic denim. The weaving process of weft elastic denim is basically the same as that of ordinary denim, that is, the manufacturing group is: pulp dyeing process - weaving - finishing - shrinkage. The organizational structure of elastic denim is mostly the twill structure of warp floating surface. During weaving, the elastic weft yarn should be extended as far as possible, so that the elasticity of the cloth will be produced after the weft shrinkage of the finished cloth, Compared with ordinary denim, elastic denim has a particularly large shrinkage; The direct shrinkage is between 2% and 4%, while the transverse shrinkage is between 16% and 22%. The shrinkage difference between the two is large, which is the most important characteristic of elastic denim.
2. Problems needing attention in pattern design of elastic jeans. Because the shrinkage of elastic denim varies greatly between the vertical and horizontal directions, we must pay attention to testing the accurate shrinkage before making the paper sample, and then cut the paper sample according to the proportion. In terms of style design, it is best to adopt the traditional five bag style, that is, the front bag is a front curved bag and a famous watch bag; The back pocket is a three pointed open patch pocket. The seam bag with oblique and straight insertion in the front bag should be avoided as far as possible, because the transverse shrinkage of the cloth is large, and the bag mouth is easy to deform after completion. Compared with the shape after washing, it will not deform much before washing. It is sewn with elastic denim. The bag shape before washing is ten points straight, but after washing, the bag shape may turn into a shape folded inward on both sides, When making the paper pattern, the width of the back bag shall be widened appropriately.
3. Problems needing attention in sewing elastic jeans
(1) The stitch density and stitch spacing should be large, preferably 2.5cm, 7 to 8 stitches. Because the denser the stitch spacing, the less elastic the stitch is, which can not match the elastic characteristics of the cloth; (2) Adjustment of pressing shoe pressure: the pressure of pressing shoe shall be adjusted to the minimum, especially for single needle flat car and double needle flat car. The pressure of pressing shoe shall be adjusted to: when the turning tooth is reduced and the pressing shoe is separated from the turning tooth, the gap between pressing shoe and needle plate can pass through a 0.08mm photocopy paper. Especially the part sewn in the transverse direction. Such as trouser leg and back pocket opening, so as to avoid that the sewing part in the transverse direction becomes wider and wider due to too much pressure.