Selective chemical pretreatments and post-treatments on microdenier polyester fabric for improving surface depth of colour

76-85Polyester microdenier (0.8 dpf) and normal denier (≥2dpf) multifilament fabrics have been subjected to pretreatment with different solvents and caustic soda prior to dyeing with disperse dye. The relative changes in their textile-related physico-chemical properties and structures have been evaluated by measuring weight loss, shrinkage, tensile strength, elongation, critical dissolution time and surface depth of colour in terms of K/S value. Among the three organic solvents (phenol, dimethyl formamide and nitrobenzene) used, the pretreatment with phenol shows some noticeable improvement in surface depth of colour without much affecting the above physical properties. The effect of treatment with 10% mixture of DMF-phenol (1:1) for 60 min shows lesser weight loss but inferior balance of properties as compared to the treatment with 10% phenol or 10% DMF alone. Caustic soda pretreatment using 1-5% NaOH with 0.1-0.3% catalyst always shows higher weight loss in case of microdenier polyester fabric than that in case of normal denier polyester fabric. To achieve -15% weight reduction in microdenier polyester fabric, the optimum treatment conditions are: 5% NaOH, 0.1 % hexamethylene diamine,60 min treatment time and 90°C treatment temperature. Post-treatments with silicone and organo-modified silicone emulsion, having lower refractive index than that of the polyester fibre, are beneficial for improving <span style="font-size:14.0pt;mso-bidi-font-size: 12.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:hiddenhorzocr"="" lang="EN-IN">surface <span style="font-size:14.0pt;mso-bidi-font-size:12.0pt; font-family:" times="" new="" roman","serif""="" lang="EN-IN">depth of colour by 3.6-9% where amino-silicone emulsion shows the best results.