Yarn tenacity and Elongation Test

Given various fabrics produced using SIRANG yarns, it is necessary to ensure that SIRANG yarns have sufficient tenacity and quality for different weaving machines. SIRANG regularly tests the tenacity and elongation of yarns through a tenacity testing system.

To ensure the accuracy of the test results, the SIRANG quality control lab uses a constant-rate-of-extension (CRE) tenacity testing system to accurately measure the tenacity of the polyester filament yarns. The break properties of yarns/fibers include the breaking force or tension, breaking elongation, and work of rupture. Each of these parameters is potentially important for the purpose of yarn products. For example, the breaking force is an important parameter for yarns that are to be used to lift heavy objects, whereas elongation is the most important parameter of warp yarns in fabric weaving. Moreover, rock climbing ropes need fabrics with high work of rupture rather than a large breaking force (specific tension).

Test Procedure

The initial tension, initial sample length, moving jaw velocity, and yarn count must be set in accordance with the standards before the test is run. For example, a sample length of 500 mm, a jaw velocity of 500 mm/min, and an initial tension of 0.05 CN/Dtx are set to measure the tenacity, elongation, and work of rupture of FDY with a certain denier. Iranian National Standards require a minimum strength of 4 g/denier for FDY, 2 g/denier for POY, and 3.5 g/denier for DTY dope-dyed yarn. The permissible elongation range is 18–48% for FDY, 100–170% for POY, and 17–30% for DTY.

Tenacity Test Machine (CRE)

A CRE test machine (with a constant rate of elongation) can be employed to measure the breaking force, breaking tenacity (specific tension), and breaking elongation of yarns under ASTM D2256, ISO 2062, or ISIRI 29. One end of the yarn is held by the fixed jaw, whereas the other end is fixed within the other jaw that moves at a constant rate. The CRE test machine is fully automatic and has a system to display and record forces and elongations. It can also plot the stress-strain curve for the elastic and plastic behavior analysis of yarn.