Relationship between cooling and optical properties of polyester fabric treated with TiO2 nanopigments

Abstract

The absorption of solar radiations (especially near infrared region) is the reason for solar heating the surface of object and increasing its temperature. To avoid this undesirable heating, it is possible to use some special nanopigments that can reflect the solar radiation in the near-infrared spectrum. Consequently, the thermal regulation and cooling property of fabric as a result of the surface coating is really important. This work studies the possibility of using Visible, NIR and SWIR reflective coatings on polyester fabric to reduce surface temperature when irradiated with solar radiations. Polyester fabrics were dyed with disperse dye and coated with TiO2 nanopigment with different diameters and concentrations. Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray spectroscopy (EDS), and heat box were used to characterize the coating process. Obtained results indicate that, the lower surface temperature was recorded by applying the TiO2 nanopigment on polyester fabric and selected materials can considerably increase the thermal regulation and cooling property of the polyester fabric. The pristine (white) and colored polyester fabric coated with TiO2 (500 nm diameter, 3 gr/L) has the highest reflectance throughout the NIR and SWIR regions of solar radiation. The treated polyester fabric respect to pristine polyester fabric exhibits reasonable cooling power and about 4 °C thermal regulation and cooling. Based on the obtained results by heat box system, the thermal regulation and cooling property as the temperature difference between pristine and coated fabric were increased with increasing the diameter and concentration of TiO2 nanopigments. The statistical analysis of variance (ANOVA) was used to study the effect of physical characteristics of TiO2 nanopigments (size and concentration) on the optical parameters as color difference (ΔE), reflectance factor (R) and reflectance function (K/S) and thermal regulation and cooling property as the temperature difference (ΔT). The obtained results indicate that there are good relationship and correlation between the NIR and SWIR reflectance and cooling properties.