Figure 1.2 Typical chemical groups of natural dyes 9
Figure 1.3 Fabric colouration methods 12
Figure 1.4 Exhaust dyeing line diagram 13
Figure 1.5 Schematic diagram of padding 16
Figure 1.6 Distribution of global dye demand 21
Figure 2.1 Design outline for padding natural dyes 28
Figure 2.2 Indigo formation in plants 30
Figure 2.3 Four possible stereo-isomeric dimers of profisetinidine 31
Figure 2.4 Polymers of condensed tannins 32
Figure 2.5 Solubilising reaction of indigo 34
Figure 2.6 Various types of indigo printing 35
Figure 2.7 Schematic diagram of AAS 38
Figure 2.8 Schematic diagram of ATR – FTIR 39
Figure 3.1 Padding mangle geometry 43
Figure 3.2 Laboratory scale steamer 44
Figure 3.3 Perkin Elmer Spectrum 400 FTIR 45
Figure 3.4 Varian AA 280 FS (AAS) 45
Figure 3.5 Mordanting and dyeing combinations 48
Figure 3.6 Reflectance curves of cotton fabrics dyed with A. catechu51
Figure 3.7 Reflectance curves of cotton fabrics dyed with A. nilotica51
Figure 3.8 Schematic of metal complex formation 52
Figure 3.9 Equatorially coordinated copper with cellulose 52
Figure 3.10 FTIR spectra of dyes 54
Figure 3.11 FTIR spectra of complexes formed by the two dyes in combination with copper 55
Figure 3.12 FTIR spectra of complexes formed by the two dyes in combination with iron 55
Figure 3.13 FTIR spectra of cotton fabric dyed in combination with copper as mordant
. 56
Figure 3.14 FTIR spectra of cotton fabric dyed in combination with iron as mordant..57 Figure 3.15 Comparison of colour strength (A. catechu) padded on cotton 60
Figure 3.16 Comparison of colour strength (A. nilotica) padded on cotton 61
Figure 3.17 Calibration curve for AAS 61
Figure 4.1 Schematic representation of plasma 67
Figure 4.2 APC 2000 atmospheric plasma treatment system 70
Figure 4.3 APC 2000 side view showing position of electrodes 70
Figure 4.4 Schematic sample set-up for plasma treatment 71
Figure 4.5 Effect of plasma gas on depth of shade 74
Figure 4.6 Effect of plasma gas on depth of shade 74
Figure 4.7 Effect of plasma gas on depth of shade 75
Figure 4.8 Effect of plasma gas on depth of shade 75
Figure 4.9 Effect of varying the plasma parameters on padding Caspian dye on wool fabric 76
Figure 4.10 Effect of varying the plasma parameters on padding Thar dye on wool fabric 76
Figure 4.11 One-step patterning 78
Figure 5.1 Schematic structure of chitosan 81
Figure 5.2 Line diagram of pad dyeing in the presence of chitosan 84
Figure 5.3 Reflectance curve for Caspian 85
Figure 5.4 Reflectance curve for Thar 85
Figure 5.5 Shade card for Thar dye 86
Figure 5.6 Shade card for Caspian dye 87
Figure 5.7 Comparison of sum of the K/S values for Caspian dye 87
Figure 5.8 Comparison of sum of the K/S values for Thar dye 88
Figure 5.9 Bacterial growth on agar plates for Thar (A) and Caspian (B) dyes 90
Figure 5.10 Agar plates control (A) and fabric dyed with Thar and 0.05% chitosan (B)
. 91
Figure 6.1 K-Bar hand coater 95
Figure 6.2 Modified vat pad-dyeing process 97
Figure 6.3 Schematic process sequence diagram 101
Figure 6.4 Comparison between exhaust dyeing and padding – natural indigo 102
Figure 6.5 Comparison between exhaust dyeing and padding – synthetic indigo 103
Figure 6.6 Reflectance curves – synthetic and natural indigo, 103
Figure 6.7 Effect of steaming duration on colour strength (reduced in Bath A) 105
Figure 6.8 Effect of steaming duration on colour strength (reduced in Bath B) 105
Figure 6.9 Reflectance curves natural indigo (Bath A 90 s and Bath B 6 min) 107
Figure 6.10 Printed indigo reduced using Bath A (TUD + caustic soda) 109
Figure 6.11 Reflectance curves comparing print shades from synthetic and natural indigo reduced using Bath A 109
Figure 6.12 Effect of alkali on indigo printing 110