Application of thermochromic colorants on textiles: temperature dependence of colorimetric properties

Commercial thermochromic colorants were applied to a conductive cotton fabric prepared by using nichrome/cotton core-spun yarns in weft and 100% cotton in warp. The fabrics were pretreated and coloured with thermochromic pigments in isolation, in combination with each other, or in a mixture with a non-thermochromic pigment. The weft yarns were joined to allow passage of current through the fabric to enable ohmic heat generation to increase fabric temperature. The heat generation and temperature rise could be controlled by monitoring the voltage applied. The colour of the samples changed gradually with an increase in temperature, and significantly so when the temperature of the fabric rose beyond the activation temperature of the thermochromic colorant. The temperature-dependent properties of commercial thermochromic colorants were determined using a spectrophotometer. Wash fastness of the samples was found to be fair in all cases except with the yellow colorant. Predetermined colour effects, such as camouflage or novel design, can be produced by combining thermochromic colorants with conventional pigments or thermochromic colorants with different activation temperatures.