Asian Journal of Physical and Chemical Sciences

In the present work, optimization of extraction natural dye from neem (Azadirachta indica)                        leaves with respect to dye bath concentration on silk fabric was studied before and after                      exposing to artificial daylight for 160 h. The effect of different dye bath concentrations in the range 40-240 g/L on the reflectance spectra of the unexposed and exposed silk fabric was followed by using spectrophotometric technique. The absorption coefficient, optical band gap energy and extinction coefficient as well as color strength were calculated from the reflectance data                           and the wash fastness was tested. The color parameters: the relative brightness (L*), color constants (a* and b*), whiteness index (W), color difference (∆E), chroma (C*), hue (H), and tint (T) and the CIE tristimulus values (x_r, y_r, and z_r) were also determined. The obtained results                       showed that the absorption and extinction coefficients, color strength and color parameters were highly affected by changing dye concentration. In addition, it was also noticed that the variations in the values of the optical band gap energy with increasing dye concentration may be due to the induced structural change in the system. In addition, the dyed silk samples have shown good washing fastness properties. The washing fastness grade for color change ranged from 4 to 5, whereas from 4 to 4/5 for color staining with all samples. The present study indicates that the natural dye extracted from neem leaves has good potential in textiles dyeing and meet the environmental future demands technology of high quality fantastic dyed pattern through an economical point of view.