Texturing and intermingling processes by using air-jets

The air-jet texturing (AJT) and intermingling (INT) processes are two applications of air jets used to modify the structure of synthetic multifilament yarns. The modification is performed by high-speed jets, which are created by purpose designed nozzles. The present work experimentally investigates the interrelation between properties of the yarn produced and air flow and the nozzle geometry in order to gain an improved understanding of the AJT process. Firstly, a number of industrial AJT nozzles were selected for detailed analysis. undisturbed flows created by these nozzles are investigated by means of total pressure measurements and shadowgraphy. The effect of nozzle geometry on the AJT process is investigated by using a series of systematically designed nozzles. A number of geometrical parameters of cylindrical type AJT nozzles are specified for successful texturing, after assessing performance of the nozzles by stabilising zone tension and the properties of yarns produced. It is found that large exit length and slightly diverging main duct are beneficial for texturing. Also the trumpet shaped exit profile is found to be necessary for adequate texturing. Low tilt angle of air inlet hole is recommended. Effect of wetting on AJT is investigated with special reference to yarn-to-yarn and yarn-to-metal friction. It is found that when the supply yarn is treated with water interfilament friction prior to the nozzle is reduced, but increased slightly in the texturing area. The former may make relative movement of filaments easier. The latter is considered to be one of the ways through which wetting improves the process, since it assists anchoring the loops in the yarn. Subsequently high-speed cine-photograpy is deployed to visualise the AJT process inside and around exit area of the nozzle. The nozzle used has rectangular cross-section and one glass wall, which allows to see inside the main channel. It is found that for successful texturing loop formation and fixing the loops are both necessary. The INT process is investigated by using again several systematically designed nozzles with reference to correlation between nip frequency and nozzle geometry. Rectangular nozzles are found to be performing adequately, depending on their dimensions. The nozzles with area ratio smaller than unity perform adequate intermingling. It is also found that small aspect ratio is benefical in terms of nip frequency. A better understanding of the INT is achieved by means of SEM, high speed video and cine-photography and yarn tension measurements. The yarn is found to be necessary to run constantly against the incoming flow to reduce missing nips.