Effect of Workwear Fabric Characteristics on the Changes in Tensile Properties of Sewing Threads after Sewing

Abstract

During sewing at high speed, the needle thread issubjected to repeated tensile stresses, heat, bending,pressure, torsion and wearing. These stresses act onthe thread repeatedly and the thread passes 50-80times through the fabric, the needle eye and thebobbin case mechanism, before getting incorporatedinto the seam. As a result both the sewing thread andthe yarns in the fabric get abraded/ severed during theseaming process. A number of researchers observedthat there could be 30% to 40% strength loss in thecotton needle thread after sewing. The extent ofdamage becomes more critical if the fabric beingused is of a dense, thick and heavy construction. Anumber of studies have been carried out on threadstrength loss after sewing, but the impact of fabriccharacteristics on thread strength loss is stillunexplored. In this paper, the effect of weight andfabric composition of workwear fabrics, on thechanges in the tenacity, breaking elongation andinitial modulus of the needle thread has been studied.The tenacity and breaking elongation loss increasewith increase in fabric weight for staple threads andremain unchanged for core spun threads. The loss ininitial modulus increases for polyester threads asfabric weight increases, and decreases for cottonthread. When sewn on polyester-cotton fabric ofsame weight, the cotton thread shows decrease intenacity and breaking elongation loss, whereas loss ininitial modulus increases. The polyester core spunthreads show exactly opposite change, i.e. tenacityand elongation loss increase and loss in initialmodulus decreases when sewn on polyester-cottonfabric.