Influence of different preparation and dyeing processes on the physical strength of the Ingeo† fibre component in an Ingeo fibre/cotton blend. Part 1; Scouring followed by dyeing with disperse and reactive dyes‡

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.     

Effect of heat setting on dimensional stability and dyeing properties of poly(lactic acid) fibres

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.     

Study of the removal of a disperse dye stain from a polyester/elastane blend

Polyethylene terephthalate and elastane fabrics were treated with azo disperse dyes in the same dyebath at 130 °C for 0, 30 and 60 min and then reduction cleared. The dyes adsorbed on each fabric were extracted using monochlorobenzene, in order to determine the amount of disperse dye in each of the polyethylene terephthalate and elastane fabrics, as the dyeing time was increased. It was observed that the amount of dye on the polyethylene terephthalate increased, while that on the elastane decreased, as the time at 130 °C increased from 0 to 60 min. After reduction clearing, the partition ratio of disperse dyes between the polyethylene terephthalate and the elastane increased. The dyed polyethylene terephthalate/elastane blend indicated that those dyes, which exhibited high partition ratios (polyethylene terephthalate:elastane), exhibited correspondingly higher wet fastness properties.     

Influence of Eri silk fibre on the physical characteristics and dyeing properties of Eri silk/cotton blended yarn

Different blending ratios of Eri silk and cotton fibres were prepared. The optimum bleaching condition chosen for the blends containing 0–25% silk content was the oxidative bleaching method, whereas the blends at 50–100% should be bleached using the two‐stage bleaching method (oxidative bleaching followed by reductive bleaching). These conditions did affect the force–displacement characteristics of the fibres with no yield point. X‐Ray diffraction results showed that the percentage of crystallinity of the cotton yarn tended to increase after bleaching, whereas the percentage of crystallinity of the Eri yarn decreased marginally. Dyeing properties of the blended yarns were investigated using warm‐dyeing reactive dyes. Percentage exhaustion and the colour yield of the blends tended to decrease with the increasing silk content. Shade variation was observed on the yarns at different blend ratios. This was expected to be caused by the different physical nature of Eri silk and cotton fibres. Consequently, the dye uptake and visual shade of each dye on the two fibres were different.     

Influence of different preparation and dyeing processes on the physical strength of the Ingeo† fibre component in an Ingeo fibre/cotton blend. Part 2; Bleaching followed by dyeing with disperse and reactive dyes‡

A study has been conducted to examine the effect of a vigorous alkaline scour–bleaching preparation, followed by high temperature dyeing, reduction clearing and a reactive dyeing process on the physical strength of the Ingeo fibre component of an Ingeo fibre/cotton blend. The results indicate that the physical strength will be retained at a technically‐ and commercially‐acceptable level provided that prolonged high temperature processing times are not employed.     

Correlation between the shade of an azo disperse dye on poly(ethylene terephthalate) and poly(lactic acid) fibres with its spectroscopic properties in selected organic solvents

A series of azo disperse dyes was synthesised and the purified, synthesised dyes were characterised by proton nuclear magnetic resonance, thin‐layer chromatography and melting point measurement. The spectroscopic properties of the dyes in solution were studied by dissolving the dyes in ethyl acetate and methyl benzoate. These were seen as mimicking the environment of the dye when inside dyed poly(lactic acid) and poly(ethylene terephthalate), respectively. Reflectance spectra of the dyes on both polyester substrates were also measured in order to correlate with the spectroscopic properties of the dyes in solution. The absorbance spectra of the dyes in solution exhibited a hypsochromic (lower wavelength of maximum exhaustion) shift when dissolved in ethyl acetate, compared with methyl benzoate. The occurrence of this yellow shift was attributed to the lower polarity of ethyl acetate compared with methyl benzoate. The colour of the dyes in ethyl acetate solution was also brighter and stronger (higher molar extinction coefficients) than that in methyl benzoate. Most of the synthesised dyes exhibited high levels of exhaustion onto the two polyester fabrics. However, the visual colour yields, for those dyes having approximately the same high level of exhaustion, were different, the dyed poly(lactic acid) being stronger (higher K/S value) as well as being yellower and a trace brighter than the dyed poly(ethylene terephthalate). This difference correlated well with the solvatochromic study of the dyes in ethyl acetate and methyl benzoate solution.     

Thermal migration of selected disperse dyes on poly(ethylene terephthalate) and poly(lactic acid) (Ingeo†) fibres

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.