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Excessive spun yarn hairs have been proved to be a key factor in deteriorating the yarn frictional property,[1] fabric pilling[2] and resultant fabric dyeing evenness.[3] Thus, many methods are applied to reduce yarn hairiness. For the spinning process, some novel spinning methods are employed to reduce spun yarn hairs, such as compact spinning,[4],[5] air-ring spinning[6]-[9] and surface-contacting spinning.[10],[11] Compact spinning can produce smooth yarns by pneumatic condensation to control the out-most peripheral strand fibers before twisting.[4],[5] Air-ring spinning employs vortex airflow to wrap hairs onto the yarn surface, decreasing spun yarn hairiness.[6]-[9] Surface-contacting spinning wraps protruding hairs onto the yarn surface or into yarn during the yarn rolling on the contact surface.[10],[11] During the winding process, yarn hairiness rises sharply due to severe rapid rubbing and pulling[12] ; therefore, a special apparatus is employed to depress excessive hairiness increase by generating vortex airflow, wrapping yarn hairs.[13]-[15] To avoid pulled sized hairs during the sizing process, a grooved device is used to conduct single yarn sizing, adhering nearly all hairs onto the sized yarn surface.[16]
The distribution of reduced hairiness onto the yarn surface may influence other yarn properties, such as yarn unevenness CVm (i.e. coefficient of mass variations), yarn imperfections and yarn tensile properties. Previous studies reveal that the concentration of surface hair wrappings increases yarn thick places, deteriorating yarn unevenness CVm.[9],[10] Precluding the concentration during the hair-wrapping, the yarn imperfections and unevenness CVm could avoid obvious deterioration; this proposition needs theoretical and experimental support. A previous experimental study found that yarn hairiness weighs as high as 12.82% for combed Ne 60S cotton yarns.[17] Then there is a positive expectation of proper hair wrappings to improve yarn appearance and tensile properties, which are awaiting an extensive and comparative investigation.
Based on the aforementioned technical issues and potential research requirements, this paper focuses on rethinking and improving hair wrappings on the yarn surface. A theoretical model was also built to analyze and predict how the hair-wrapping style influences yarn properties. Then, well-designed experiments were conducted to prove our theoretical proposition.
Modeling of hair wrapping on the yarn surface
The distribution length model of yarn surface hair wrappings
A previous study revealed...