Camouflage of cotton fabrics in visible and NIR region using three selected vat dyes

Abstract

To provide camouflage in near infrared (NIR) region and imitate reflectance profile of greenish leaves, cotton fabrics were dyed with three selected vat dyes, namely C.I. Vat Blue 6, C.I. Vat Yellow 2, and C.I. Vat Red 13. Reflectance curves of two types of fresh greenish leaves were measured as standard reference. Transmittance curve of vat dyes in acetone solution indicated that selected vat dyes have suitable structure to provide camouflage in NIR region. According to reflectance profiles, reflectance curve of Vat Blue 6 has more similarity with that of green leaf at the concentration of 0.85% owf (on weight of fiber) and 1.2% owf in comparison with those of C.I. Vat Yellow 2 and C.I. Vat Red 13. Cotton fabrics were dyed with different mixtures of the dyes to obtain a standard shade to reach camouflage in visible range. Chromatic values of dyed fabrics were measured (CIE1976 L*, a*, and b*) and two standard shades of the 1948 US army pattern, NATO and forest green, were obtained on cotton fabrics with ΔECMC < 2. Reflectance profiles of these two shades were located between the reflectance of green leaves. So, two vat dyes were introduced to camouflage dyes group, C.I. Vat Blue 6 and C.I. Vat Red 13, and used to achieve NATO green and forest green shades for first time. All dyed samples showed good fastness properties. The effect of washing and light exposure on camouflage properties of fabrics in visible and NIR region was inconsiderable. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 200–207, 2014