Indian Journal of Fibre & Textile Research Vol. 34, March 2009, pp. 11-19 Effect of linear density, twist and blend proportion on some physical properties of jute and hollow polyester blended yarn Sanjoy Debnath a & Surajit Sengupta National Institute of Research on Jute & Allied Fibre Technology, 12 Regent Park, Kolkata 700 040, India Received 1 January 2008; revised received and accepted 17 April 2008 The effect of yarn linear density, twist density and blend proportion on bulk density, tenacity, breaking extension, work of rupture, flexural rigidity, hairiness and friction of jute-hollow polyester blended yarns made on conventional jute spinning system has been studied. Box and Behnken experimental statistical design has been used to study the individual and interactive effects of independent variables. It is observed that the bulk density and coefficient of static friction increase initially with the increase in yarn linear density as well as twist. After reaching the maximum value, further increase in these parameters decreases the properties. In case of all jute yarn, the maximum tenacity reaches at 195 twists/m and 145 tex. However, for 60% jute blended yarn, these values are 210 twists/m and 155 tex. The minimum breaking extension attains at 135 tex with 220 twists/m for all jute yarn and 185 tex with 220 twists/m for 60% jute blended yarn. The specific work of rupture decreases with the increase in jute content in the blend. The maximum specific work of rupture is obtained at 185 tex with 230 twists/m in 60% jute blended yarn. However, in case of all jute yarn the maximum values are obtained at 200 twists/m and 135 tex. The specific flexural rigidity of yarn is higher for all jute yarn compared to that for jute blended yarn. The lowest yarn hairiness is observed at 160tex with 215 twists/m for all jute yarn. Keywords: Bulk density, Flexural rigidity, Hairiness, Jute, Hollow polyester fibre, Static friction, Tensile properties, Yarn friction 1 Introduction Jute, the annually renewable and one of the cheapest commercially available high modulus natural fibres, is well known to all as packaging material and carpet backing. Apart from this, today jute finds a diversified path as blended products, such as furnishing material, interior decoration, fashion garments, jute ornaments and blankets. 1 Blending of man-made fibre with jute introduces some improved properties, like bulk, elongation, regularity, luster, etc. Thus, the properties of blended yarn depend on type of fibre, quantity and method of blending. Ali et al. 2 has studied the properties of sulphonated jute fibre and its blends (65% jute) with cotton, rayon, acrylic, polyester and silk waste, and compared their fabric properties with pure cotton and pure sulphonated jute fabrics. Cumming and Atkinson 3 reported that blending of 10% of terylene with jute is suitable for sewing thread in jute coal bag. Rotor-spun short staple jute-polyester yarns have been texturised and compared with apron draft jute frame spun texurised yarn. 4 It is found that the jute and polyester (70:30) blended rotor-spun yarn shows the optimum result. Recently, Debnath et al. 5 studied various properties of bulked yarn developed from blends of jute and hollow polyester and compared that yarn with commercial woollen and acrylic bulk yarns. The study shows that jute-hollow polyester blended bulk yarn has higher bulk over similar commercial yarns due to low yarn packing. It is evident that various physical properties and their coefficient of variations of jute-hollow polyester and jute-viscose blended yarns are superior compared to all jute yarn. 6 The main objective of this study is to understand the property-parameter interactions of jute-hollow polyester blended yarns prepared on the conventional jute spinning system. Hollow polyester is different than any other synthetic fibres and still its blending with jute is not explored. It is expected that the blending of hollow polyester with jute may improve some properties like bulk, resilience, softness, luster and fineness of the yarn. Jute has high modulus, good luster and high rigidity. Hence, in the present work, attempts have been made to study the effect of yarn linear density, twist density and blend ratio on the bulk density, tenacity, breaking extension, work of rupture, flexural rigidity, hairiness and friction of jute- hollow polyester blended yarns. _________ a To whom all the correspondence should be addressed. E-mail: sanjoydebnath@yahoo.com