The effect of filament initial modulus on textured yarn properties is studied, keeping other parameters constant. Initial modulus has a major influence on textured yarn properties. An increased initial modulus causes poor texturizability and therefore inferior textured yarn properties such as poor bulk, stability, loop frequency, and higher nep level. A study of the effect of filament linear density on textured yarn properties shows that finer filaments produce better quality yarns as far as loop frequency, bulk, and instability values are concerned, but they also produce higher numbers of neps

We report on the characteristics of two sorts of neps from wet and dry air-jet textured yams and the effects of process variables on their formation. We discuss structural configurations and opening forces using both machine and videographic methods.Wet texturing produces fewer neps at all pressures, but yet counL does increase with increasing pressure, whether the process is wet or dry.

Nep formation, a drawback in the air-jet texturing process, can be controlled to some extent by suitable choices of certain factors related to the process. In order to understand how these variables influence nep formation in air-jet texturing, a central composite design is formulated and four variables—air pressure, texturing speed, mechanical stretch, and overfeed—are considered. Analysis of the results indicates that air pressure, texturing speed, and overfeed contribute significantly to nep formation, but mechanical stretch has little or no effect.

Experiments conducted to investigate the reasons for nep formation in air-jet tex turing indicate that neither periodic tension variations in feeder yarn nor differences in tension levels between the two parallel fed ends have any significant effect on nep formation. Insufficient and inhomogeneous opening of filaments inside the nozzle is primarily responsible for nep formation; higher levels of interfilament friction and lower vortexing intensity contribute to insufficient opening of the filament bundle. We therefore suggest that neps in air-jet textured yarns are formed because the filament bundle does not open in the nozzle. Partial opening results in one kind of nep, while complete lack of opening causes another kind in the succeeding part of the unopened section of the yarn.

Results are reported for experiments conducted to correlate different structural in homogeneity parameters of air-jet textured yams, such as number of neps per thousand meters, number of thick places per thousand meters, CV% of yam linear density, CV% of yam strength, and CV% of loop frequency. All these parameters are highly correlated, and so the various indices of structural inhomogeneity can be represented by only one of them. Number of neps per thousand meters has been suggested as the index of structural inhomogeneity of air-jet textured yarns due to its quick and easy assessment, high degree of sensitivity to changes in raw material and process parameters, and very high correlation with other parameters.