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

Abstract

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.

Dyeing and Fastness Properties of Disperse Dyes on Poly(Lactic Acid) Fiber

“…This points out that the shade obtained on PLA differs from that on PET. It was reported that the shade difference was observed on PLA and PET when the two fibers were dyed at the same level of visual depth (Suesat et al, 2011). In addition, a brighter shade obtained on PLA was found (Choi & Seo, 2006;Blackburn, 2005).…”

“…from the solvatochromism study of disperse dyes mentioned in our previous work (Suesat et al, 2011). The light absorption capacity of the dye is influenced by polarity of the polymer medium.…”

“…Refractive indices of ethyl acetate and methyl benzoate are 1.372 and 1.517, respectively (wypych, 2001) being closely similar to those of PLA (1.35-1.45) and PET (1.54). As a chemical structure resemblance of ethyl acetate and methyl benzoate with the two polyesters, they could be used to dissolve disperse dyes and imitate the environment of the dyes in PLA and PET and their influence on the dye could then be monitored (Suesat et al, 2011).…”

“…From their study, the dyes with the δ values below 25.0 (J.cm 3 ) 0.5 had high sorption whereas those with δ values above 25.0 (J.cm 3 ) 0.5 exhibited lower than 70% sorption on PLA when dyed at 110 o C and the dyes with the δ values close to that of PLA were mainly azo dyes. In our work (Suesat et al, 2011), a correlation between the solubility parameter and the dye exhaustion was also established from a set of experimental data obtained from 22 azo disperse dyes on PLA and PET. The δ values were also calculated by means of group contribution methods mentioned in Karst & Yang (2005).…”

An efficient route for the synthesis of some monoazo disperse dyes derived from nicotinic acid derivatives

“…The considerable biological and medicinal activities of nicotinic acid and its derivatives [2][3][4][5] have promoted recent interest in synthesis of new nicotinic acids of potential biological activities. Although condensation reactions of arylhydrazonals with active methylene nitriles were originally reported to afford pyridazin-6-imines [6], more recent studies have demonstrated that arylazonicotinates are also formed in some of these processes [7][8][9].…”