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A short study has been conducted to examine the efficiency of different alkaline reduction-clearing conditions on Ingeo [poly(lactic acid)] fibres, dyed with disperse dyes. The results indicate that the preferred conditions are 15 min at 60 °C in the presence of 2 g/l sodium carbonate and 2 g/l 'hydros', conditions which avoid any significant change of shade by colour loss and lead to optimised wash fastness.

Reactive dyes exhibit a higher level of initial exhaustion, in the presence of small concentrations of electrolyte, on never-dried lyocell than on never-dried viscose and modal. This difference is particularly noticeable in the case of high substantivity bis-monochloro-s-triazinyl reactive dyes, which exhibit the same differentiated performance on the corresponding dried fibres. Low salt quantities (comparable to those used for applying direct dyes to cellulosic substrates) can therefore be used for applying high substantivity dyes and effect chemicals by an exhaustion process to both never-dried and dried lyocell substrates.

Exhaust application of a given reactive dye to never-dried lyocell, viscose and modal fibres gave virtually identical levels of exhaustion on each fibre, whether in the presence of salt alone or in salt plus alkali, as well as similar levels of fixation. This suggests that the accessibility and reactivity of the three never-dried fibres for selected reactive dyes, during a typical exhaust dyeing process, are the same.

A study has been carried out to correlate the wet fastness properties of dyed knitted fabrics, derived from both poly(ethylene terephthalate) and poly(lactic acid) (Ingeo) fibres, with the thermal migration properties of the disperse dyes during heat treatment. The results indicate a greater amount of disperse dye at the surface of the Ingeo fibre fabric than the poly(ethylene terephthalate) fabric, after post heat-setting using the conditions needed for fabric stabilisation, correlating well with its slightly lower wash fastness properties.

A study has been conducted to examine the effect of different preparation and dyeing processes on the physical strength of the Ingeo fibre component of an Ingeo fibre/cotton blend. An alkaline scouring process (for the cotton), followed by a two-bath, two-stage dyeing process in which the Ingeo fibre underwent a simulated dyeing with disperse dyes, followed by the cotton being dyed with reactive dyes, caused minimal deterioration to the strength of the Ingeo fibre. However, it is considered that problems might arise if the Ingeo fibre was subjected to prolonged dyeing times, particularly at neutral or alkaline pH, e.g. if an excessive number of shading additions needed to be carried out.

A study has been conducted into the effect of heat setting on the dimensional stability and dyeing properties of spun and false-twist texturised poly(lactic acid) yarn. It has been shown that acceptable levels of dimensional stability can be achieved after heat setting for 30-45 s at 130 °C, false-twist texturised yarn exhibiting greater shrinkage than spun yarn. The exhaustion level and visual colour yield of a number of disperse dyes have been evaluated on each type of poly(lactic acid) yarn and shown to be essentially independent of the time of heat setting.

This paper addresses the relative effects of softeners having different properties and their method of application (exhaust vs pad) on the colour fastness of poly(lactic acid) fabrics dyed with a range of disperse dyes with different levels of hydrophobicity. A comparison was made with a correspondingly finished polyethylene terephthalate fabric. Possible relationships between the levels of hydrophilicity/hydrophobicity of the dye, and softener, and the colour fastness were explored. Finally, the amount of dye thermally migrated into the finish on the softened poly(lactic acid) and polyethylene terephthalate fabrics was examined in comparison with their colour fastness. Softened poly(lactic acid) fabrics dyed with CI Disperse Red 167.1 exhibited more thermal migration, and hence lower colour fastness, than the corresponding polyethylene terephthalate fabrics. Conversely, softened poly(lactic acid) fabrics dyed with Dianix Deep Red SF exhibited less thermal migration, and hence better colour fastness, than the corresponding polyethylene terephthalate fabrics. Overall, no clear relationship was found between the hydrophobic nature of the disperse dye and the hydrophobic character of the softener on the colour fastness. © 2010 The Authors. Coloration Technology © 2010 Society of Dyers and Colourists.

This study investigates the influence of different finishing conditions on the amount of thermal migration and the wet fastness properties of selected red disperse dyes on polylactic acid fabrics. A comparison was made with a correspondingly finished polyethyleneterephthalate fabric, with a specific objective being to identify the conditions that would give optimum wet fastness to the polylactic acid fabric. A greater thermal migration of dye was observed on the polylactic acid compared with polyethyleneterephthalate fabric under the same heat treatment conditions, resulting in a lower level of wet fastness. The lowering in wet fastness of dyed polylactic acid fabric on processing occurs mainly as a result of thermal migration of disperse dyes during the drying stage at 110 °C. © 2009 The Authors. Journal compilation © 2009 Society of Dyers and Colourists.