Investigation on the effect of titanium dioxide nano particles on camouflage properties of cotton fabrics

Cotton fabrics were dyed with three commercial vat dyes in order to provide camouflage in Vis-NIR regions and imitate reflectance profile of greenish leaves. To investigate the effect of nano particles on camouflage properties of dyed fabric, nano particles of TiO₂ were applied on dyed fabrics using pad-dry-cure method. The nano TiO₂ padded dyed fabrics were investigated using scanning electron microscopy (SEM). Reflectance curves of coated dyed samples with different concentrations of nano TiO₂ were measured. Results showed that in both of the standard shades, nano TiO₂ increases the reflectance value in NIR region and with increasing the concentration of nano TiO₂, the reflectance curves of samples tend to show the maximum reflection of greenish leaves (deciduous leaves) in NIR region. Chromatic values (CIE1976 L*, a*, and b*) and color difference (according to CIECMC color difference ΔE*cmc (2:1)) of each of the coated samples were measured using the reflection spectrophotometer. By considering the influence of white color of nano TiO₂ on green shade of dyed cotton fabrics and increasing the color difference (between coated samples and the standard shades of the 1948 U.S army pattern) in visible range, optimum concentrations of nano TiO₂ for development of camouflage properties on cotton fabrics in both NIR and visible region were determined. These values for NATO and forest green shades were 0.75 % and 0.5 %, respectively. Fastness results showed that both of the samples have acceptable color fastness. The effect of washing and exposure to light on camouflage properties of coated dyed fabrics in visible (in term of chromatic values) and NIR region (in term of spectral reflectance) was investigated when those were coated in optimum concentrations of nano TiO₂. The results showed that the effect of after treatments (washing and exposure to light) on surface color spectral characteristics and camouflage properties was inconsiderable.