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Colour of flax fibres in regard to different pretreatment and dyeing processes
Darinka Fakin, Alenka Ojstršek, 2008, original scientific article

Abstract: The main objective of this work was to compare the colour of different pretreated (alkaline, acidic and enzymatic) and dyed (conventional and ultrasonic-assisted) flax fibres, to establish the impact of various parameters on dyeing kinetics. Flax fibres were dyed using two direct dyes of different chemical structures and molecular mass. Diffusion profiles were established by the application of Fick's Law and dyeing behaviour was studied by means of online spectrophotometry. Finally, the dyed samples were colorimetrically evaluated and colour differences and colour strengths were subsequently calculated. The results provided evidence that a dye molecule's size has a greater influence on the exhaustion degree, migration and diffusionthan individual pretreatment processes. The determined diffusion coefficients indicated superior dye mobility and faster diffusion into the fibres when ultrasonic power was used in comparison with conventional process. Nevertheless, the colour depth obtained was found to be low after ultrasonic dyeing using a larger dye molecule, implying part degradation of CIDirect Red 80 (and total degradation of small-size dyestuff, CI Direct Red 81).
Published: 31.05.2012; Views: 865; Downloads: 73
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3.
The impact of ultrasonic-assisted dyeing on ecological parameters
Alenka Ojstršek, Darinka Fakin, 2008, published scientific conference contribution

Abstract: The main contribution of our research was to compare the impact of the conventional dyeing process and the power ultrasonic technique on dye-bath exhaustion and, consequently, on dye-bath effluents during the dyeing of four dissimilar fabrics (cotton, viscose, wool and polyamide) using chemically-different dyestuffs (reactive, direct, acid and 1:1 metal complex) at two concentrations, regarding different operational parameters, in order toestimate the environmental impact of numerous parameters and dyeing systems.The efficiency of various dyeing procedures was verified by measuring on-line absorbance, followed by the calculation of exhaustion rate. After dyeing, the selected pollution parameters were monitored in dye-baths effluents, i.e. pH, total organic carbon (TOC), chemical oxygen demand (COD), and biochemical oxygen demand (BOD5). The obtained results indicated superior exhaustion of dyestuffs during ultrasound assistance in comparison to conventional dyeing, thus causing a reduction in dyeing time and energy consumption. Moreover, the selected pollution parameters were diminished in all the dye-baths effluents after ultrasonic dyeing, thus also enhancing environmental protection.
Keywords: exhaust dyeing, ultrasound, dye-bath effluents, colourimetry, pollution control
Published: 31.05.2012; Views: 1051; Downloads: 15
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4.
Colour of polyester thread, in regard to different dyeing procedures and dye-bathsć ph
Darinka Fakin, Alenka Ojstršek, Alenka Majcen Le Marechal, 2008, published scientific conference contribution

Abstract: The aim of the presented research was to investigate the impact of different dyeing procedures (conventional two-baths and one-bath) and dye-bathsć pH (acidic and alkaline) on the exhaustion of five disperse dyestuffs, differing in colour (yellow, red, blue, violet and black). The dyeing of polyester thread was carried-out at two concentrations (1 and 3%). The concentration of dye residual in dye-bath effluents were determined by absorbance measurement, followed by colourimetrical evaluation of dyed samples, and colour differencescalculation. The obtained results indicating superior dye exhaustion throughout alkaline one-bath procedure in comparison to conventional polyester dyeing that affect also on reduction of dyeing time, amount of dye-bath wastewaters, and energy consumption.
Keywords: polyester sewing, dyeing, disperse dyestruffs, colourimetry
Published: 31.05.2012; Views: 951; Downloads: 22
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5.
Analysis of reactive dyestuffs and their hydrolysis by capillary electrophoresis
Alenka Ojstršek, Aleš Doliška, Darinka Fakin, 2008, original scientific article

Abstract: The objective of the presented research was to examine the potential of capillary electrophoresis (CE) for the analysis of structurally different reactive dyestuffs, their activation and posterior hydrolysis, with special focus on optimization of the working conditions. Preliminary, the effect of various additives to the background electrolyte on the resolution improvements versus migration time of Reactive Black 5 as a model dyestuff was investigated. Based on these results, the electropherograms of eight commercially interesting reactive dyestuffs of various chemical structures and their converted forms upon alkaline pH were carried-out. In order to examine the behavior of the reactive dyestuff during the dyeing process, the dye-bath absorbance was monitored throughout the Reactive Black 5 exhaustion, and the conversion of the dye's form was highlighted using the CE technique. The obtained results unequivocally prove that CE could offer a fast and efficient detection method of structurally different reactive dyestuffs, as well as their hydrolysis products in the dye-baths and effluents later on.
Keywords: capillary electrophoresis, dyes, hydrolysis
Published: 31.05.2012; Views: 1233; Downloads: 49
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Removal of vat and disperse dyes from residual pad liquors
Vera Golob, Alenka Ojstršek, 2005, original scientific article

Abstract: The efficiency of three wastewater treatment techniques, coagulation/flocculation, adsorption and ultrafiltration, has been studied for the removal of vat and disperse dyes from residual pad liquors. Three inorganic coagulants Al2(SO4)3 18H2O, FeSO4 7H2O, FeCl3 6H2O and commercial cationic flocculant, as individuals and in combination, were tested for the coagulation/flocculation methods. Granular activated carbon was used as an adsorbent in the adsorption technique. Ultrafiltration was performed using a polyethersulfone membrane with a molecular weight cut-off of 10 kDa. Dye removal was evaluated as the difference between concentrations of dyes in pad liquors before and after a particular treatment using absorbance measurements.The obtained results indicated over 90% of dye removal using appropriate coagulants and only 40% using activated carbon. The best results, dye removal over 98%, were achieved using the ultrafiltration technique.
Keywords: textile dyeing, disperse dyes, wastewater, decoloration, wastewater treatment, coagulation, flocculation, adsorption, ultrafiltration, vat dyes
Published: 01.06.2012; Views: 1454; Downloads: 79
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The impact of corona modified fibres' chemical changes on wool dyeing
Darinka Fakin, Alenka Ojstršek, Sonja Čelan Benkovič, 2009, original scientific article

Abstract: The main contribution of the present work was to study the impact of Corona-treated wool fabricsć induced surface properties on dye-bath exhaustion, in order to optimize different dyeing systems. Firstly, the differing chemical aspects of a woven wool fabricćs surface were determined using two dissimilar analytical skills (XPS and polyelectrolyte titration). With the intention of establish the ability of low-temperature plasma treatment to change wool fibre morphology which could have an impact on sorption properties, fabrics were dyed with blue acid and blue metal-complex dyes, and dyeing behaviour were studied by means of on-line VIS spectrophotometry. Finally, dyed samples were colourimetricaly evaluated and colour differences calculated. The results provided evidence that the overall carbon C 1s content was decreased while oxygen and nitrogen atoms were increased when using ionized air for fabric modification. It has also been noted that the amount of positive-charged functional groups in various pH ranges are higher for Corona-treated wool fabric in comparison with the untreated that improves hydrophylity and dyeing properties.
Keywords: Corona treatment, wool, metal-complex dye, acid dye, sorption, colourimetry
Published: 01.06.2012; Views: 1320; Downloads: 70
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