High-quality sewing thread should have sufficient tensile strength, smooth and flawless surface, uniform thread dryness, good elasticity, small shrinkage, good color fastness, good chemical resistance, and good sewability. Therefore, national standards have strict regulations and requirements for the technical indicators of heavy duty sewing thread.
The items include: special count, ply count, twist, single yarn strength and strength variation coefficient, color fastness (especially wash fastness and rub fastness), boiling shrinkage, length and allowable tolerance, allowable number of joints, and appearance defect limits.
The evaluation of finished product quality is based on the testing of finished products according to the technical requirements stipulated by national standards. The lowest item is used as the basis for evaluating the grade of sewing thread, which can be divided into first-class, second-class, and special-grade.
The sewability of sewing thread is a comprehensive evaluation index of sewing thread quality. It indicates that under specific conditions, sewing thread can sew smoothly and form good stitching. Obviously, the quality of sewability of filament thread for sewing will directly affect production efficiency, sewing quality, and the performance of sewn products.
Under specific conditions of speed, needle size, stitch length, and test material, the sewability is reflected by the number of thread breaks or the length that can be sewn. The fewer the number of thread breaks or the longer the sewing length, the better the sewability.
The test material is made into one layer, two layers, three layers to ten layers. Under specific conditions of speed, needle size, and stitch length, the more layers the thread can sew through, the better the sewability.
When sewing under specific conditions of speed, needle size, stitch length, and test material, by gradually increasing the tension through the tension adjustment device of the sewing machine, the sewing thread breaks when the tension is increased. The greater the tension required for the sewing thread to break, the better the sewability.
As a material widely used in the textile industry, the quality and sewability of sewing thread have a significant impact on production and manufacturing. Therefore, it is essential to understand the quality requirements, evaluation methods, and sewability of sewing thread. Only with a solid understanding of these basic knowledge can we make better choices and use sewing thread, providing better guarantees for production and manufacturing.