Twist structure of friction-spun yarns: Part I - Open-end DREF-II yarns

122-129The twist structure of friction-spun yarns has been explored through the development of an accurate method of twist measurement. It has been found that the optical method, based on the measurement of fibre helix angle and helix diameter through the well-known tracer fibre technique, is the most accurate technique for measuring twist. The twist values obtained by this method have been found to correlate well with those given by other methods of twist testing. Corresponding correlation coefficients and the regression equations have also been derived. The position of the integrating fibres along the length of the fibre assembly zone does not influence the amount of twist inserted in open-end DREF-II yarn. The level of twist is determined by the fibre and process parameters under which the yarn is spun. Twist level drops with the increase in fibre length from 25 mm to 44 mm but shows a slight increase thereafter. The coarser yarns show lower twist than the finer ones. The use of coarser fibres results in lower amount of twist in the yarn while an increase in suction pressure increases it