The purpose of this study is to investigate the thermoregulatory properties of polyethylene terephthalate (PET) 3D knitted materials with bioceramic additives which are highly absorbing far-infrared (FIR) radiation. Ceramic materials are well-known and useful for thermal insulation applications. In order to compare different types of ceramic additives and coating methods for their incorporation into textile, several types of ceramic compounds with heat-retaining function were selected: germanium (Ge), aluminum (Al) and silicon (Si) additives were applied by impregnation in squeezing padder and titanium (Ti) by the screen printing method. The thermoregulatory properties (thermal resistance, heat-retaining effectiveness and air permeability) of 3D PET knits with bioceramic additives were estimated. In this study scanning electron microscopy (SEM) images were used to analyze the morphology of coated fabrics, X-ray fluorescence spectroscopy (XRF) analysis was applied to evaluate the number of minerals with high heat capacity in each formulation used for treatment. The knits coated with a formulation containing Ti ceramic additives demonstrated the most effective thermal behavior. Furthermore, better heat accumulation effectiveness of Ti ceramics containing knits was confirmed by Fourier transform infrared spectroscopy (FTIR) analysis. It was also determined that 3D knitted fabric with Ti ceramic additives showed the highest emissivity among tested samples and the implication is that this sample radiates its energy more efficiently than others.

The study presents an investigation of thermoregulatory processes of ceramic-containing textile materials used in cold environments. Bio-ceramic additives have a heat-retaining function caused by its far-infrared (FIR) radiation. Storing heat at a high temperature, bioceramics can radiate heat to the body when the temperature outside drops. In order to improve the thermal efficiency of fabrics primarily worn next to the skin, our intention was to increase the active surface area of the ceramic-containing textile material. For this purpose a combined knitted PET fibre textile material was used, which was treated with ceramic additives using different application methods. Tests were performed where specimens were kept in a constant temperature oven, then placed on a cold surface, and the temperature decrease of the specimens was periodically recorded in a given time period. The results revealed that the highest heat accumulation was determined in screen-printed fabric with continuous coating, and the lowest-in PET fabric knitted of bio-ceramic containing fibres.