FIBRES & TEXTILES in Eastern Europe October / December 2007, Vol. 15, No. 4 (63) 46 n Introduction Blending different types of fbres is wide- ly practiced to enhance the performance and aesthetic qualities of fabric. Blended yarns from natural and man-made fbres have the particular advantage of success- fully combining good properties of both fbre components, e.g., comfort in wear with easy-care properties. Furthermore, cotton/polyester blending has many ad- vantages such as less pilling, less static electrifcation, easier spinning, better evenness for sliver, roving and yarn [1]. These advantages also permit an in- creased variety of products and a better marketing advantage. Hairiness is one of these most impor- tant yarn characteristics, which affects weaving, knitting, dyeing and fnishing processes in textiles. Yarn hairiness is ex- pressed in terms of the number or length of fbres directed outward from the yarn surface. The parameters of fbres and machines atg all production stages are known to be infuential on yarn hairiness. When, as a consequence of technological advances, machine speeds are increased and high productivity are required, yarn hairiness become a very undesirable pa- rameter, which was to be measured and controlled. Effects of the material and the machines on yarn hairiness, and the measurement methods of hairiness, have been studied by numerous authors [2 - 10]. This study aimed to predict the hairi- ness of cotton/polyester blended rotor yarns using blend ratios and yarn count as predictors. It is a critical problem in fbre blending technology to choose appropriate types of fbres and blend ratios depending on the fnal product’s requirements. n Materials and method Materials In this study cotton was one of the com- ponents in blending. Properties of the cotton fbres measured on Uster HVI 900 (High Volume Instrument) test equipment are presented in Table 1. The second component of the prepared blends were polyester staple fbres pro- duced by SASA-DupontSA. Test results for the linear density, length, tensile and elongation properties of the polyester sta- ple fbres are presented in Table 2. Method Experimental design A simplex lattice design with two rep- lications at each design point was con- structed to determine the combinations of mixture ratios of two fbre types [11, 12]. Let X 1 , X 2 , ..., X p denote the proportions of “p” components of a mixture, then : 0 ≤ X i ≤ 1 i = 1, 2, ..., p A {p, m} simplex lattice design for “p” components has the ratios of each component taking m + 1 equally spaced values from 0 to 1. X i = 0,1 / m,2 / m,...,1 i = 1, 2, ..., p (1) The number of design points in A{p, m} simplex lattice design is, (2) In this study, A{2, 4} simplex lattice de- sign shown in Figure 1 was used to de- termine cotton/polyester blends. Design points (blend ratios) used in this study are shown in Table 3. Production of cotton / polyester blended OE rotor yarns Cotton and polyester fbres were proc- essed and blended on a traditional short-staple (carding) spinning mill (Matesa Textiles Corp. of Turkey). The processing steps for both cotton and polyester were modern short-staple A Statistical Model for the Hairiness of Cotton/Polyester Blended OE Rotor Yarns Pınar Duru Baykal, Osman Babaarslan, *Erol Rizvan Department of Textile Engineering, *Department of Industrial Engineering, Çukurova University, 01330-Balcalı/Adana, Turkey. E-mail: pduru@cu.edu.tr teksob@cu.edu.tr rerol@cu.edu.tr Abstract This study aimed to predict the hairiness of cotton/polyester blended rotor yarns using blend ratios and yarn count as predictor variables. A simplex lattice design with two replications at each design point was constructed to determine the combinations of mixture ratios of the fbre types. Cotton/polyester blended slivers were used to produce rotor yarns with fve different counts on a laboratory-type rotor spinning machine (quickspin). Mixture-process crossed regression models with two mixture components and one process variable (yarn count, linear density) were built to predict hairiness properties. All statistical analysis steps were implemented, using Design-Expert statistical software. Key words: yarn hairiness, rotor yarns, experimental design, fbre blending. Table 1. HVI test results for the cotton fbres. Kind of parameter Linear density, dtex Length, mm Unf., % SFI Tenacity, cN/tex Elonga- tion, % SCI CSP Rd b C-G mean value 1.50 28.95 83.2 6.50 28.5 6.70 142 2277 77.5 8.5 31-1 s.d. 0.25 0.84 0.92 0.80 1.19 0.18 6.47 47.08 1.21 0.50 - CV, % 6.63 2.90 1.11 12.29 4.09 2.72 4.54 2.07 1.56 5.85 - Table 2. Test results for the polyester fbers. Kind of parameter Linear density, dtex Staple length, mm Tenacity, cN/tex Elongation at break, % mean value 1.59 33.31 0.74 22.90 s.d. 0.13 0.26 0.573 5.426 CV(%) 9.09 0.78 8.39 23.69