Study on Air Permeability and Warmth Retention Ability of Polyurethane Foam Plying with Fabrics Chi-Wai Kan 1, a * , Clare Man-Ching Ko 1, b , Kittisak Ariyakuare 2, c , Wasana Changmuong 2, d and Rattanaphol Mongkholrattanasit 2, e * 1 Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong 2 Department of Textiles Chemistry Technology, Faculty of Industrial Textiles and Fashion Design, Rajamangala University of Technology Phra Nakhon, Bangkok, Thailand a tccwk@polyu.edu.hk, b man-ching.ko@connect.polyu.hk, c kittisak.a@rmutp.ac.th, d wasana.c@rmutp.ac.th, e rattanaphol.m@rmutp.ac.th * Corresponding author Keywords: Warmth retention ability, Air permeability, Polyurethane foam, Plying, Fabric Abstract. In this study, we evaluated warmth retention ability of polyurethane foam (non-laminated and laminated) plying with fabrics. The warmth retention ratio, measured by KES-F7, was used for expressing the thermal property of plied samples. Experimental results revealed that the warmth retention ratio of samples that were plied with fabrics were higher than the foams in plain (i.e. without plying with fabric). For non-laminated foams, the fabrics had generally increased the warmth retention ratio by 10%. For laminated foams, the increase was about 4 to 5% in the warm retention ratio. By comparing the warmth retention ratio between the non-laminated foams and laminated foams, laminated foams have higher heat retention power. Being a close-to-skin garment, the air permeability is an important factor to determine their usage. Thus, we examined the air permeability of the different samples and the results were discussed properly. Introduction Thermal comfort is the condition of mind which expresses satisfaction with the thermal environment (ISO 7730). Air temperature, humidity, air movement, mean radiant temperature, body heat generation and clothing are the vital factors in determining thermal comfort. Human must maintain a constant core temperature of about 37°C, and a rise or fall of 5°C is usually fatal [1, 2]. Thermal comfort is associated to the human thermal balance between heat gain and loss of the human body. Heat is mainly generated from the metabolism of food and muscles activity, and a very portion is from the sun. Body loses heat to the environment through four ways, conduction, convection, radiation and evaporation, and the rate of heat lost is controlled by the temperature gradient between the skin and environment. The human body is rarely in a thermal steady state, it varies under different physical activity and environment conditions [2, 3]. Polyurethane foam plying with fabrics is usually used for making intimate apparel which is in close contact with human skin. Thus, the thermal comfort behavior of such materials is very important for industrial application. In this study, we will evaluate the warm retention property of different foams (non-laminated and laminated) plied with different fabrics. Air permeability is defined as the rate of air flow passing perpendicular through a known area under a prescribed air pressure differential between the two surfaces of a material (ASTM D123- 13a). Materials that are air permeable are usually permeable to water. Hence, the water-vapour permeability and liquid-moisture transmission are closely correlated to air permeability. The thermal resistance of a fabric is highly dependent on the amount of entrapped still air [4], fabric with high air permeability means air can move in and out the fabric easily, thus reduces the warmth keeping ability of the fabric. The air permeability is influenced by the fabric structure and the fibre moisture regain. Fabrics that are formed by closely packed yarns usually have poorer air permeability. Fibres Applied Mechanics and Materials Submitted: 2016-07-21 ISSN: 1662-7482, Vol. 866, pp 233-239 Revised: 2017-01-13 doi:10.4028/www.scientific.net/AMM.866.233 Accepted: 2017-01-16 © 2017 Trans Tech Publications, Switzerland Online: 2017-06-06 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (#85056105-31/03/17,16:47:57)