Indian Joural of Fibre & Textile Research Vol. 28, March 2003, pp. 65-70 Characterization of grey and dyed cotton fbres as well as waste at diferent stages of rotor spinning process S M Ishtiaque Department of Textile Technology, Indian Institute of Technology, New Delhi 110 016, India and A Das ' Northern India Textile Research Association, Sector 23, Raj Nagar, Ghaziabad 201 02, India Received 19 September 2001; revised received and accepted 11 December 2001 A detailed analysis of the properties of grey and dyed (reactive dyed and natural dyed) cotton fibres including the waste materials at different stages of rotor spinning process has been carried out. Significant changes in length-related parameters are observed in each mechanical processing, the effect being more prominent in case of dyed fibres where the frictional coefficient is high. The effects of opning roller speed and its type on the fibre characteristics have also ben reprted. Keywords: Blow room droppings, Open-end spinning, Opening roller speed, Short fibre content, Span length 1 Introduction A close monitoring of fibre characteristics at different stages of spinning is very important for its proper realization to yarn properties. Few studies 1.2 have beenreported onpropertiesof grey cotton fibres at different spinning preparatory processes. Based on the available information on fbre characteristics at a particular stage of spinning, one can do necessary changesinthe process parameters and take necessary corrective action in the subsequent process. It is a very wel-known fact that any mechanical process, like beating and carding, changes the fibre characteristics in terms of length-related parameters and trash content. To have more uniformity and consistencyin theshadeofcottonyam,particularlyin open-end spinning, the present trend is to mix the dyed fibre in blow room stage instead of dyeing at y stage. It is very important to know the characteristics of grey as well as dyed fbres at various spinning stages to assess the quality of the ultimate yam. The efforts made in this area are insignificant. "o whom all the correspondence should be addressed. Present address: Department of Textile Technology, Indian Institute of Technology, New Delhi 110 016, India Phone: 26591413; Fax: 0091-011-26851103; E-mail: apurba_das@hotmail.com Indifferentpreparatory stagesofspinning,wasteis bound to generate although the technological advancementisabletoreducethewasteleveltosome extent. In addition to the waste minimzation, industries are now reusing the waste generated at different spinning stages, particularly in coarser counts for cost minimization. It is very important to knowthepropertiesof wastematerialforitsefective reuse. No detailed information is available on characterization of grey and dyed cotton wastes in spinning. In spite of its inherent adantages in productivity, therotor-spunyamsufers from fewdeficiencies,like low strength, consistent deterioration in yam quality and running performance due tothe accumulation of dust particles in the rotor groove 3 - 5 , and poor fbre length realization due to the lower spinning-in coefficient 6  The action of the opening roller during rotor spinning results in better individualization and cleaningof fibresandatthesametimefbre breakage also takes paIce 7 - 9 • The present paper repos the properties of grey and dyed (natural and reactive) fbresincludingthewastematerialatdiferentstages of rotor spinning process. The effects of opening roller speed and its type on the characteristics of fibres and waste have also been reported. The study was carried out on a large scale under the actual running condition in industry_ As both the grey and dyed cottons were processed in the set of machinery