Saminathan Ratnapandian

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Wavelength (nm)
Figure 5.3 Reflectance curve for Caspian


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Wavelength (nm)
Figure 5.4 Reflectance curve for Thar

2. Effect of chitosan

Figure 5.5 and Figure 5.6 show shade cards that bring out the effect of adding chitosan to the padding liquor. In order to quantify the shades, the sums of the K/S values are depicted in Figure 5.7 and Figure 5.8, assuming the value obtained for fabric dyed without chitosan as the benchmark (100%).

It can be seen from the shade cards and graphs that the addition of chitosan to the dye liquor affected the depth of shade irrespective of the dye–mordant combination. In general, a uniform dye distribution was observed on the fabric padded in the presence of chitosan. Davidson and Xue [174] and Canal et al. [172] have reported similar

levelness of shade in exhaust dyeing experiments conducted after pretreatment of fabric with chitosan. They attributed the evenness of shade to the film-forming characteristic of chitosan, which provided an increased number of reaction sites for the dye. Other researchers have exploited the film-forming feature in diverse areas [183-185].
However, this feature might have inhibited dye uptake during initial trials in this study when the fabric was pretreated with 0.05% chitosan followed by padding. It was likely that the low quantity of dye liquor taken up by the pretreated material was insufficient to overcome the chitosan film barrier and dye the fabric.

Figure 5.5 Shade card for Thar dye

Figure 5.6 Shade card for Caspian dye


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