Design of passive heating textile structures by managing natural radiation energies

In modern textile applications, passive heating structures designed through the management of natural radiation energies are utilized in various technical fields such as cosmetics and medical sectors, in addition to clothing, due to their enhanced comfort and energy-saving benefits. In this study, composite films with heating properties were obtained by adding zinc oxide (ZnO), tourmaline, and pumice particles into a sodium alginate (NaAlg) matrix, which is a natural polymer. These film solutions, optimized for optical and heating properties, were applied as a finishing treatment on cellulosic nonwoven fabric to create heating fabrics. The basic chemical and morphological analyses of the films and fabrics were conducted using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR), while the crystal structure of the particles and composite structures was analyzed through X-ray Diffraction (XRD). The ability of films and fabrics to manage body radiation energy in the mid-infrared (MIR) wavelength range and reflect it back to the body in the far-infrared (FIR) wavelength range was evaluated through reflectance and emissivity graphs obtained via attenuated total reflectance (ATR) FT-IR analysis. The performance of absorbing sunlight was investigated using UV-VIS-NIR spectroscopy, where reflectance and absorption graphs were obtained. Heating performance tests were conducted under FIR lamp using a hot plate system developed within an ongoing TUBITAK Project. Additionally, since the intended end-use of the developed fabric is a medical or cosmetic mask, essential physical, mechanical, permeability (air), liquid absorption, and transfer tests (absorption time, wetting test, absorption capacity) were performed to determine other performance characteristics of the fabric. According to the results obtained, the tourmaline-containing film showed the highest reflectance performance in the mid-infrared radiation (MIR) range (7-14 µm), while the ZnO particle-containing film exhibited the highest emissivity according to the emissivity results. In UV-VIS measurements, tourmaline- and pumice-containing films absorbed sunlight more efficiently in the visible light range (400-700 nm). The high optical performance of tourmaline- and pumice-containing films was also valid for heating, as the films achieved heating levels of 9.39 °C and 9.07 °C, respectively, compared to their non-particle forms. Consequently, composite solutions containing tourmaline and pumice were applied to the nonwoven fabric at two different polymer loading rates. Fabric results showed that the composite fabric with pumice exhibited better performance than the fabric with tourmaline in terms of reflectance and emissivity based on FT-IR results. The heating performance tests conducted with the hot plate system revealed that the fabric with low polymer loading containing pumice achieved the highest temperature difference (4.18 °C). However, unlike the heating performance, the heat retention during cooling was lower in composite-applied fabrics, with particles negatively affecting this feature. When examining the performance and comfort parameters of the fabrics, it was observed that polymer application resulted in an expected increase in weight, a decrease in breaking strength in the machine direction, an increase in the crosswise direction, and a decrease in elongation compared to the raw fabric. Although the necessity is not as garment fabrics, the bending rigidity values, which are important for the selected cosmetic use, increased as expected with polymer loading. Tourmaline particles significantly stiffened the fabric compared to pumice-containing applications. As expected, air permeability values decreased with the application, with the fabric containing a low polymer loading of tourmaline showing the closest values to the raw fabric. The best results in terms of liquid absorption and transfer properties were obtained for the fabric with pumice-containing high polymer loaded one. Tourmaline-containing fabrics exhibited the highest liquid absorption capacity. In conclusion, the fabric with pumice-containing composite application was determined to be the most suitable structure for a personal or medical care product, such as cosmetic face masks, by demonstrating superior performance in FT-IR reflectance and emissivity, heating performance, air permeability, and liquid absorption and transfer properties. It is thought that these fabrics, by reflecting body heat back to the skin and providing a long-lasting warming effect, could support more effective absorption of active ingredients delivered to the skin. The fact that higher performance was achieved at a lower polymer loading rate provides both economic and fabric performance advantages. It is also believed that such passive heating structures, considering the biodegradable nature of the NaAlg and selected particles, could be used in multifunctional similar products for environmentally friendly body applications without energy consumption. Keywords: Personal thermal management, natural radiation, passive heating, tourmaline, pumice, sodium alginate