Sandwich Structures Reflecting Thermal Radiation Produced by the Human Body

Abstract

Far infrared (FIR) textiles are a new category of functional textiles that have presumptive health and well-being functionality and are closely related to human thermo-physiological comfort. FIR exerts strong rotational and vibrational effects at the molecular level, with the potential to be biologically beneficial. In general, after absorbing either sunlight or heat from the human body, FIR textiles are designed to transform the energy into FIR radiation with a wavelength of 4–14 μm and pass it back to the human body. FIR textiles can meet increased demand for light, warm, comfortable, and healthy clothing. The main aim of this research is to describe the procedure for creating the FIR reflective textile layer as part of multilayer textile structures that have enhanced thermal protection. To develop the active FIR reflecting surface, the deposition of copper nanolayer on lightweight polyester nonwoven structure Milife, which has beneficial properties of low fiber diameters, good shape stability and comfort, was used. This FIR reflective layer was used as an active component of sandwiches composed of the outer layer, insulation layer, active layer, and inner layer. The suitable types of individual layers were based on their morphology, air permeability, spectral characteristics in the infra-red region, and thermal properties. Reflectivity, transmittance, and emissivity were evaluated from IR measurements. Human skin thermal behavior and the prediction of radiation from the human body dependent on ambient conditions and metabolic rate are also mentioned. The FIR reflective textile layer created, as part of multilayer textile structures, was observed to have enhanced thermal protection.

A Review of Textiles Reflecting FIR Produced by the Human Body

“…In case of an air gap between the human body and clothing, heat is propagated through radiation at wavelengths from 4.4 μm to a maximum of 9.4 μm (FIR) under ambient conditions. Even indoors and in a sedentary state, 50% of the heat generated by the human body is dissipated through radiation [1]. FIR thermal energy is found to have positive effects on the body [3,8].…”

“…The heat balance influences the thermal state of a person. It is the relationship between the amount of heat produced by the organism and the amount of heat removed from the organism to the surroundings [1]. In the case of thermal equilibrium, when there is no accumulation of heat in the body, the heat produced by the body is dissipated in various forms, namely, radiation, flow, conduction, evaporation, and respiration.…”

“…Standard textiles act as an insulator of thermal conduction and convection but with very limited ability for thermal radiation reflection. A few textiles can realize efficient reflection of farinfrared (FIR) produced by the human body, but they have some limitations [1]. The FIR textiles are designed to retroreflect thermal radiation back to the human body.…”

“…FIR textiles are a category of functional textiles that have presumptive health and well-being functionality. Molecules are impacted by the rotational and vibrational forces of FIR [1]. FIR textiles are designed to transform the energy into radiation with a wavelength of 4-14 μm and reflect it back to the human body.…”

“…Accumulation of water vapor at low ambient temperatures may result in hypothermia. Sometimes perforated reflective foil addresses this issue, but it results in large openings, which reduce thermal insulation properties [1]. Therefore, the better solution is to only use the porous textile layers with a surface reflective layer [2][3][4][5][6][7].…”