Influence of polymer grade, process parameters, and capillary modification on the shape factor of noncircular cross-section fibers

In the textile industry, more than 20 % of the obtained revenue goes back to product innovations. Here, an intensified use of fibers with a noncircular cross-section is observed. In particular for noncircular cross-section fibers, the development of spinning nozzles is very time consuming. This goes back to the die swell effect as for which the relaxation of the polymer at the die exit leads to a low conformity between the desired and the realized cross-sectional shape (shape factor). Therefore, multiple iteration steps are necessary to obtain the geometry of the capillaries of the spinning nozzle. Hence, the production of individual shaped fibers is inefficient and limits the degree of innovation of fiber and textile producers. Within this research study, the effects of polymer grades, process parameters and capillary modifications on an increase of the shape factor of noncircular fibers was investigated for polyethylene therephthalate. It was found that an intrinsic viscosity < 0, 8 and an extrusion temperature of 295 °C lead to an increase of the shape factor. Modifications of rectangular capillaries of a spinning nozzle positively affect the aspect ratio of as-spun fibers.