Measuring loop lengths of elasticised knitted fabrics

The methods for loop length measurement have mostly been developed for knitted fabrics made from conventional yarns. When measuring the loop lengths of knitted structures made from highly extensible staple yarns, problems arise because of an uncontrolled yarn extension at the low stresses. The present study proposes a test method for knitted loop length determination in which variable preloads are applied. In the study, the loop lengths measured on an INSTRON dynamometer using variable preloads and a HATRA Course Length Tester using a fixed preload were compared. The results demonstrated that knitted structures made from elasticised yarns exhibit only small changes in loop length after relaxation. The addition of elastane does not significantly influence loop lengths for fabrics knitted using the same machine, the same cam setting and relaxed by the same process. The loop lengths measured on an INSTRON dynamometer exceed the loop lengths measured on a HATRA Course Length Tester.