Role of Hair Coverage and Sweating for Textile Friction on the Forearm
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Role of Hair Coverage and Sweating for Textile Friction on the Forearm Jingchun Lyu1,2 · Novaf Özgün1 · David J. Kondziela1,3 · Roland Bennewitz1,3 Received: 22 June 2020 / Accepted: 8 September 2020 © The Author(s) 2020
Abstract Friction of textiles on the human forearm is an important factor in comfort sensations of garments. We built an experiment to measure friction for textiles sliding on the forearm under loading conditions which are characteristic for wearing shirts or jackets. The hair coverage of the participants’ forearm was quantified by image analysis of photographs of the arm in the region of contact. Friction results for five standard textiles suggest to treat hair coverage in two classes. Sweating after physical activity leads to an increase of friction by factors of 2 to 5 for participants with less hairy forearms, while an increase by a factor of 1 to 1.7 only was found for participants with more hairy forearms. We introduce a method of wetting the forearm of study participants in a controlled way with water, which results in similar friction as for the sweating forearm after physical activity. The method allows for efficient studies of the role of skin moisture for friction including varying hair coverage of the skin. Keywords Skin friction · Textiles · Sweating · Hair · Comfort sensation
1 Introduction Friction is generally believed to be a key ingredient in comfort sensations of textiles, as expressed in the wide-spread use of the friction parameter in the Kawabata evaluation system to analyze the handle of textiles [1–5]. The importance of low friction and the role of friction fluctuations in perceived pleasantness has been confirmed in a panel-base study for wide range of materials [6]. Hand friction was found to have strong negative correlation with comfort sensations for military garments [2]. Frictional properties of textiles were judged coherently by a panel as sticky-slippery attribute and showed a good correlation with overall comfort ratings [7]. It was shown that a friction experiment which is more sensitive to the textile’s hairiness had better correlation with perceived comfort in a prickle test [8]. However, friction coefficients measured with commercial textile testing * Roland Bennewitz roland.bennewitz@leibniz‑inm.de 1
INM – Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany
2
Department of Materials Science and Engineering, Saarland University, 66123 Saarbrücken, Germany
3
Department of Physics, Saarland University, 66123 Saarbrücken, Germany
systems depend on the probe shape and on the direction of sliding, and the relation between friction results of different testing systems is difficult to predict [9]. It is therefore important to measure textile friction on skin in a relevant geometry in studies motivated by comfort sensations. When physical activity was included, discomfort as reported by a panel was shown to correlate to frictionrelated attributes such as stickiness and fabric cling for the sweat-wetted skin in contact
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