Influence of Structural and Process Parameters on Mechanical Behaviour of Elastane Yarns Cruz J. 1,a Carvalho R. 1,a , Sohel R. 1,a , Fangueiro R. 1,a , Coutinho G. 2,b and Pereira M. 2,b 1 University of Minho, Center for Textile and Technology, Campus de Azurém, Guimarães, Portugal 2 Barcelcom, Tamel S. Veríssimo, Barcelos, Portugal julianacruz@det.uminho.pt Abstract In this work, the influence of various structural and process parameters (such as linear density of core and cover and draw ratio) on the mechanical behaviour of elastane yarn has been thoroughly investigated. According to the experimental results, elastane yarns with high linear density core and cover and produced using higher draw ratio showed the best mechanical properties in terms of both strength and extension. Keywords: Compression garment, elastane yarn, mechanical properties . 1. Introduction Compression garments are frequently applied in two main areas: medical, which includes different sub-sectors such as orthopedics, aesthetics, rheumatology, among others, and sports involving different modalities [1-3]. The main application of compression garment is for treating venous insufficiency, for example, treatment of varicose veins. However, it has many other applications such as for treating burns, fatigue, dislocations, muscle fatigue, sprains and low blood pressure. It is also used and recommended for long flights to avoid the occurrence of deep vein thrombosis and postpartum recovery [3]. Compression garment helps to control unforeseen, sudden and uncomfortable movements due to the act of coughing or sneezing and this is very important, for example, during the post-operative period. These products are also widely used in patients undergoing plastic surgery and / or cosmetic and orthopedic surgeries. After surgery the use of this type of garment helps to improve blood circulation, minimize swelling, and prevents the accumulation of potentially harmful fluids to the human body, allows quick recovery so that the patient can return to normal life in a relatively short period. Additionally, they are used to support the areas which were subjected to surgery and help the skin to regain its previous contours and new features [3]. Compression garments are also used in the sports clothing to improve the performance of athletes. The use of knitted fabrics composed of elastane inlay yarns in combination with other type of knitting yarns (e.g. polyamide) is a common practice to produce these garments, in order to achieve required degree of compression and elasticity. Elastic fibre such as spandex has very high extension, more than 200%/ and excellent elastic recovery [4]. Elastic fibers are opening new paths in search of more comfortable clothing. Properties such as elasticity and recovery have become key features in almost all types of clothing, from fashion to ready-to-wear, high-performance sportswear and medical garments. Elastane yarns used in compression garments are usually wrapped by cotton or polyamide cover yarns. Different types of wrapping process are used to produce these yarns such as single covering, double covering, core-spun, core twisting and air covering [5]. These processes are schematically shown in Fig. 1. (a)Single-covering (b)Double-covering (c)Core-spun (d)Core-twisting (e)Air-covering Fig. 1- Different types of wrapping process The wrapping process as well as the properties of core and the cover can be adjusted to tailor the properties (stiffness and elasticity) of the hybrid yarns, which in turn, control the performance of the compression garment [6]. To address this issue, in the present paper, the influence of structure (linear density of elastane core and polyamide cover) and production parameters (drawing ratio during covering) on the mechanical behaviour of elastane yarns have been thoroughly investigated and