Study on Seating Comfort of Polyurethane Multilayer Seat Cushions
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ght © 2020 KSAE/ 11702 pISSN 12299138/ eISSN 19763832
STUDY ON SEATING COMFORT OF POLYURETHANE MULTILAYER SEAT CUSHIONS Junho Moon1), Tridib Kumar Sinha1), Sung Bok Kwak2), Jin Uk Ha3) and Jeong Seok Oh1)* Department of Materials Engineering and Covergence Technology, RIGET, Gyeongsang National University, Jinju 52828, South Korea 2) R&DB center, Duckyang Ind. Co., Ltd, 105 Gwanggyo-ro, Suwon 16229, South Korea 3) Lightweight Materials R&D Center, Korea Automotive Technology Institute, 303 Pungse-ro, Cheonan 31214, South Korea
1)
(Received 18 June 2019; Revised 18 November 2019; Accepted 8 December 2019) ABSTRACTInstead of a monolayer, multi-layered cushion can be promising to develop more comfortable automotive seat if the layer materials are properly selected. In this study, we have examined the seating comfort of different types of multilayer seat cushions. Polyurethane foams (PUFs) of three different hardness, memory foam, and technogel were used in different combination to prepare four types of multilayer seat cushions. The short-term seating comfort of the seat cushions has been investigated in terms of hardness, initial hardness factor (IHF), modulus irregularity factor (MIF), sag factor (SF), and hysteresis loss as derived from the indentation force deflection (IFD) curves. Long-term comfort has been compared to the respective stress relaxation behavior of the seat cushions. It has been observed that both the short and long-term conditions of comfort are not only influenced by the characteristics of the upper layer, but also by the bottom layer (i.e., supporting material). The present work will help the seat designer to consider the material characteristics for fabricating a good automotive seat on the basis of the desired features needed to provide traveling passengers with proper short- and long-term comfort. KEY WORDS : Automotive seat, Seating comfort, Polyurethane, Polyurethane foam, Multilayer seat cushion
1. INTRODUCTION
the type of polyurethane (PU) raw material and the recipe (Mok et al., 2012; Kim and Park, 2013). Hardness of the PUF is known to be controlled by its isocyanate index (Lee et al., 2017). In recent years, PU based commercial products such as a memory foam and a technogel are being used in seat pads (Quan, 2009; Mason, 2016; Smith, 2018). Use of those comercial products especially technogel was further extended towards the automotive industry. For instance, a concept car named as “Bertone Pandion” designed with the “technogel” based seat was exhibited in the Geneva Motor Show (2010) (Smith, 2018). The basic constituent of PUF, memory foam and technogel is the polyurethane. These three materials are chemically related but very much different from each other. PUF is springier than memory foam whereas technogel provides stability like a solid and deformation like a fluid. Generally comfort is defined as “the pleasant and satifying feeling of being physically or mentally free from pain and suffering” (Millet and Pignède, 2001). However, as the comfort is a subjective evaluation and
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