9—the Properties of Air-Textured Continuous Filament Yarns

Instability Tests for Air-Jet Textured Yarns

“…Instability, as expected, shows an increase with increasing air pressure (Figure l9a), indicating a deterioration of yarn quality. This can be attributed to the higher number of loops at increased air pressure [23], which also increases the probability that many of these loops will be removed under the loads applied. An increased number of loops also causes the load to be shared by a reduced number of parallel filaments in the yam, which in turn contributes to increased yarn instability.…”

“…In 1965, during the early days of air-jet texturing when pretwisted yarns were used as raw material, Wray [23] observed that the textured yarn untwisted under the applied loads; he therefore claimed that the value of instability measured by any method that did not prevent untwisting included additional elongation due to removal of twist. Hence he devised an alternative method in which he made use of the Instron constant rate-of-elongation tensile tester, which did not suffer from losing yarn twist during testing.…”

“…Wray [23] claimed that the percentage permanent elongation in the textured yarn was obtained by this method, by subtracting the percentage elongation of the supply yarn (e p ) from the percentage elongation of textured yarn (e t ). The implication was that the elongation of textured yarn under an applied load also included the elastic deformation of the constituent filaments, i.e., elongations of the individual filaments also contributed to the instability of the textured yarn.…”

“…Wray [23] also devised a quicker method of measuring yarn instability based on principles similar to the Instron tensile tester method. This technique incorporated the use of a strainometer, which imposed a 5% constant strain on the yarn as it passed continuously over rollers.…”

“…Research directed towards the understanding of the air-jet texturing process can be cited as far back as 1960s, but it has recently continued at an increased pace. A brief review of previous research and the history of industrial nozzle development can be found in publications by Wilson [2l], Acar et al [2], Wray and Acar [24], and Acar [l]. The research work by Wray [22,23] The work we report in this paper is part of continuing research using a Heberlein HemaJet T 100 [l4] and a single-head texturing machine purpose-designed and built at Loughborough University of Technology to give maximum flexibility to the processing parameters.…”