RJTA Vol. 17 No. 3 2013 50 Comfort Characteristics of Knitted Active Sportswear: Heat and Mass Transfer M. Manshahia and A. Das* Department of Textile Technology, Indian Institute of Technology, New Delhi 110016, India ABSTRACT Thermo physiological comfort is an important sportswear criterion in terms of sportsmen’s comfort and performance. In this study, heat and mass transfer of active sportswear were evaluated. Heat transmission was measured by thermal resistance; relative water vapour permeability was measured to assess moisture vapour transmission; air permeability was measured to determine air passage; and sweat response was measured by water absorption, specific flow rates and drying time. It was observed that the structural parameters of fabric and the cross-sectional shape of filaments significantly affected the comfort characteristics of knitted active sportswear. Keywords: Active Sportswear, Thermo Physiological Comfort, Filament Cross-Sectional Shape, Knitted Fabric Structure 1. Introduction Heat stress is of great concern in active sports. For tennis, metabolic heat production is at 880W, and for soccer, 1330W, (Brotherhood, 2008), which can lead to high sweat rate in the range of 1.5- 2 l/h for and go up to 2.5 l/h in hot and humid conditions due to additional convective and radiative heat loads (Shirreffs, 2005). There are four modes of heat transfer to maintain the thermoregulation of a human body: Conduction, Convection, Radiation and Evaporation, in which evaporation is exploited where the high heat of vaporization gives the cooling effect (Das & Alagirusamy, 2010). Clothing provides a microclimate between the body and the external environment and acts as a barrier to heat and vapour transfer between skin and the environment (Parsons, 1994). The comfort of sportswear is determined by its moisture vapour resistance and moisture accumulation (Fan & Wang, 2008). It was reported that clothing with higher moisture absorption enhances the performance of baseball players (Park et al., 2006). Product knowledge is very important to increase the quality and sales of any textile product (Li et al., 2005) which can be measured by various Contemporary tools (Li et al., 2006). Active sportswear is mostly made of polyester knitted fabrics. Polyester with a modified cross section like hexachannel in coolmax gives more comfort due to its rapid liquid transmission and drying. The combination of polyester and viscose in a two-layer knitted structure has better wickability but slower release of moisture (Fangueiro et al., 2010). In two layer fabrics, the inner layer made of hydrophobic filaments and the outer layer made of hydrophilic fibre increase the transfer from the inner to the outer layer by capillary action (Long, 2003). The biomimetic fabric structure, mimicking the taper of water conduits in trees, has greater initial water absorption rates, one-way transport capacity and air permeability (Chen et al., 2009). Two-layer fabrics using TENCEL® on the outer layer give better moisture absorption and buffering, equal moisture spreading, the same drying rate, equal wet cling behaviour, a better balance of water vapour permeability and thermal comfort, and a less synthetic look and Handle as compared to 100% polyester sportswear(Berichte, 2006). The coarser and modified profiles of polyester are more comfortable, showing higher water vapour permeability, higher air permeability and increased thermal resistance due to their high porosity (Varshney et al., 2010). Air permeability and water vapour permeability reduce with a decrease in the fibre diameter and an increase in * Corresponding author. Tel.: +91(11) 26591413; Fax: +91(11) 26581103 E-mail address: apurba@textile.iitd.ernet.in