The internal structure of sheath fibre in DREF-3 yarn

This paper is concerned with a study of the structure and twisting mechanis m of sheath fibres in DREF-3 yarn, in which a tracer-fibre technique was us ed, The yarn was made from a polypropylene-fibre multifilament core and cot ton staple-fibre sheath, An analysis of the twist and migration behaviour o f the sheath is made to quantify the sheath structure. Process variables in vestigated are the spinning-drum speed, the yarn-delivery rate, and the sur face structure of the core component. Other process variables, e.g. the suc tion pressure, yarn count, core-sheath ratio, and number of wrapper slivers , are kept constant. The effects on the sheath structure (quantified as the total twist, twist distribution, and migration behaviour) of certain proce ss variables are discussed and possible causative factors identified. Concl usions arising from these in addition to visual observation of the sheath s tructure are used to explain the twisting mechanism of sheath fibres in DRE F-3 yarn, An attempt is rise made to explain the yarn properties for variou s process parameters on the basis of the sheath structure.