Chemical modification of cotton to improve fibre dyeability

A new fibre-reactive quaternary compound containing an acrylamide residue was synthesised and used as a cotton modification reagent. The agent was applied to cotton fabrics using a pad-bake process. It was found that the treated fibre could be dyed with reactive dyes without the addition of salt or alkali. The reactive dyes were almost completely exhausted and showed a high degree of covalent bonding with the pretreated cellulose. The effect of varying the pretreatment conditions was investigated and the optimum conditions for pretreating and dyeing were established.     

Dependence of the dyeability of modified cotton on the substituents and the nature of the dye

Cotton cellulose was chemically modified by introducing acrylamide, acrylonitrile and carboxyalkyl moieties in the form of groups or polymers. In carbamylethylated, cyanoethylated and carboxymethylated cotton, these moieties are in monomeric groups, whereas, in graft copolymers of cotton cellulose with acrylamide, acrylonitrile or acrylic acid, the moieties are in polymeric forms. These substrates were dyed independently using direct, acid, basic or reactive dyes. Results showed that at roughly equal nitrogen content, polyacrylamide–cotton graft copolymer exhibited a much higher colour strength than carbamylethylated cotton when the two substrates were dyed using basic dye. The opposite is the case for direct and reactive dyes. The acid dye produced comparable colour strengths. Similar trends were observed when the other samples were dyed with these four dyes. The results were explained in terms of microstructural changes in the physical and chemical structure of cotton caused by the etherification and grafting reactions.     

Studies of the fibre structure and dyeing properties of Calotropis gigantea,kapok and cotton fibres

Calotropis gigantea, kapok and cotton fibres are all natural cellulose fibres, but the first of these is rarely used in textile fabrics. In this study, the structure and chemical composition of these three kinds of fibre were studied, and the dyeing properties of fabrics made from each of them were compared. The purpose of this was to provide a theory basis for the application of C. gigantea fibre in the textile industry. The surface morphology and cross‐section of C. gigantea fibre in comparison with kapok and cotton were studied by scanning electron microscopy. Their fibrous structures were analysed by Fourier Transform‐infrared spectroscopy and X‐ray diffraction. The mechanical properties and water absorption capabilities were also measured and compared. Both C. gigantea fibre and kapok fibre exhibit a high degree of hollowness (80–90%), and no natural twist exists; there is a certain amount of lignin and hemicellulose in C. gigantea fibres; the crystallinity of C. gigantea fibres is 42.54%, and its crystallinity orientation index is 85.40%. C. gigantea fibre has the lowest tenacity but has the highest water content of the three kinds of fibre. The results of dyeing tests show that C. gigantea fabric has the lowest dye uptake and dye fixation.     

Effect of nanoclays on the dyeability of polypropylene nanocomposite fibres

Polypropylene clay fibres loaded with different alkylammonium-modified montmorillonite were prepared using a melt spinning technique and relationships between the structure and properties of the nanopolypropylene fibres are discussed. Experiments carried out using transmission electron microscopy showed that the chemical structure of the organic modifier and the interlayer spacing of the clay induced different dispersions of the clay, thus improving accessibility of the nano fibre. It is known that nanoclays are effective and efficient sorbents for dyes. Therefore, the dyeing behaviour of the nano polypropylene fibres with two distinct acid dyes and a disperse dye was studied and the build-up of dyes, measured as colour yield, reported. The best results were obtained when the clay was well dispersed in nanopolypropylene fibres; that is, when maleated polypropylene was added as a compatibiliser and when disperse dye was used. Good wash fastness was then obtained.     

New cationic agents for improving the dyeability of cellulose fibres. Part 2-pretreating cotton with polyepichlorohydrin-amine polymers for improving dyeability with reactive dyes

Pretreatment of cotton with polyepichlorohydrin-dimethylamine produces a modified cotton that can be dyed under neutral conditions with selected low-reactivity dyes using a small amount of salt or with selected high-reactivity dyes without salt. The dyeings of treated cotton exhibit improved colour yield and high wash fastness. The properties and the quality of the reactive dyeings are discussed.     

Effect of the ozonation process on the dyeability of mohair fibres

This work has focused on the use of ozonation in order to improve the dyeability of mohair fibres. The study was carried out using a known concentration of ozone and involved process parameters such as wet pick‐up, level of pH and treatment time. The effect of fibre ozonation was assessed in terms of colour, and test samples were also evaluated using scanning electron microscopy and Fourier transform–infrared spectroscopy. The optimum conditions of the ozonation process were determined as 60% wet pick‐up, pH 7 and 30 min. According to the experimental results, it can be concluded that ozonated mohair fibres can be dyed both at 90 and 80 °C with all dye classes without causing any decrease in colour yield. Dyeing kinetics and thermodynamics were also studied and it was demonstrated that the rate constant and the standard affinity of the ozonated sample increased.     

The effect of heat setting on the dyeability of differentially dyeable polyester fibres

Apparent diffusion coefficients of two disperse dyes for so-called easily dyeable/cationic-dyeable polyester (ED-CDPET) and cationic-dyeable polyester (CDPET) fibres of identical linear density and sulphonic acid group content have been calculated. It was found that the diffusion coefficients of dyes for ED-CDPET were far greater than those of dyes for CDPET. The dyeability at the boil without carrier, using disperse and cationic dyes on various ED-CDPET and CDPET fibres, has been studied. ED-CDPET was found to have higher dyeability at all levels of heat setting (irrespective of the dye used). The finest ED-CDPET fibres showed maximum dye uptake as a result of increased surface area. Heat setting in the taut condition reduced dye uptake.     

Compounding fibre grade polyethylene terephthalate with a hyperbranched additive and studying its dyeability with a disperse dye

A hyperbranched polymer which comprised a polyesteramide structure was used to study improvements in dyeability of fibre grade polyethylene terephthalate films. The optical measurements of the dyed samples showed that, by increasing the percentages of the dendritic additive, K/S as a dye uptake parameter changed in the presence or absence of a carrier. The amount of chroma increased while the hue did not change significantly. The dyeability of the prepared samples was attributed to the decrease in glass transition temperature and the lower crystallinity of the polymer, as studied by differential scanning calorimetry. Thus, a new fibre grade polyethylene terephthalate, which is dyeable, could be obtained, with less need to use a toxic carrier compound.     

The role of nanoclay partitioning and fibril formation on dyeability of blend nanocomposite fibres

The aim of the present work was to study the effect of microstructure and microfibril formation on dyeability of polypropylene/poly(butylene terephthalate)/organoclay blend nanocomposite fibres. The blend nanocomposite samples with the same blend ratio but varying in organoclay content were prepared via melt compounding by using a co‐rotating twin screw extruder. The microfibrillar morphology and nanoclay partitioning were studied using scanning electron microscopy and transmission electron microscopy together with rheological results. The presence of nanoclay in the form of tactoids in the polypropylene matrix accelerated the dye sorption but much greater ultimate dye uptake could be achieved for the sample in which the major part of the platelets were preferentially located inside the poly(butylene terephthalate) fibrils. Although increasing the organoclay concentration increased the ultimate dye uptake, it limited the fibril formation at higher organoclay concentration. The utilisation of a compatibiliser was found to have an enhancing effect on ultimate dye uptake. This could be explained in terms of the interfacial role of the compatibiliser in improving microfibril formation as well as partitioning a fraction of nanoclay platelets inside the polypropylene matrix.     

New cationic agents for improving the dyeability of cellulose fibres. Part 1 — pretreating cotton with polyepichlorohydrin-amine polymers for improving dyeability with direct dyes

Cotton fibres were treated with polyepichlorohydrin—dimethylamine and dyed with a selection of direct dyes. The pretreatment was found to reduce the amount of sodium chloride needed, and to increase exhaustion efficiency and perspiration fastness. The preparation and chemical characteristics of polyepichlorohydrin-dimetnylamine, the dyeing of the modified cotton and the quality of the direct dyeings are also discussed.     

The effects of dye structure and a cationic aftertreatment on the coverage of neps in cotton fabric

The effects of dye structure and aftertreatment with cationic fixative on the ability of a series of twelve direct dyes to cover neps in cotton fabrics have been examined. Colour differences before and after laundering have also been investigated.     

Intentional regulation of the structure and properties of cation-exchange fibre composites based on polypropylene fibres

An analysis of the structural features and properties of the developed cation-exchange fibre composites showed that shaped PP fibres, which are chemically inert compounds, actively participate in crosslinking processes in cation-exchange fibre materials (CEFMM) as a result of additional surface modification. Additional cryo treatment of shaped PP fibres improves their transport and sorption properties and increases the proportion of synthesized cation-exchange matrix, which is also responsible for elevated performance properties. __________ Translated from Khimicheskie Volokna, No. 6, pp. 50–53, November–December, 2005.     

Factors affecting the dyeability of cotton crosslinked with polycarboxylic acid

Improved dyeing properties of cotton crosslinked with polycarboxylic acids are produced by addition of reactive nitrogenous additives, such as alkanolamines and hydroxyalkyl quaternary ammonium salts, to the treatment formulation. Both N-methylolamides and polycarboxylic acids are effective for crosslinking cotton and bonding reactive nitrogenous additives to the cellulosic substrate, but dyeing characteristics of the finished fabrics are very different. In this study, the influence of the reactive additives and dyebath pH on the colour yields of cotton crosslinked with polycarboxylic acids and then dyed with anionic dyes were determined. Emphasis is on the dyeing properties of cotton finished with 1,2,3,4-butanetetracarboxylic acid or citric acid non-formaldehyde crosslinking agents, and alkanolamine hydrochloride or hydroxyalkyl quaternary ammonium salt additives.     

Relationship between direct dye characteristics and coverage of immature fibre neps in dyed cotton fabric

Cotton fabric containing a large number of neps was dyed with each of 17 azo direct dyes. Visible coverage of neps composed of immature fibres varied widely among the dyes. An evaluation of those structural characteristics of the dyes that might account for their differential ability to achieve coverage of neps was undertaken. Direct dyes containing more than one amino or amido group in their structure were found most likely to achieve relatively good nep coverage. Scanning electron micrographs revealed considerable variation in the types of fibres making up the individual neps in a single piece of cotton fabric. Differences in direct dye behaviour towards nep coverage were most evident with those neps composed of immature fibres with some secondary wall development.