Effect of mercerization and gamma irradiation on the dyeing behaviour of cotton using stilbene based direct dye

The dyeing behaviour of mercerized and gamma irradiated cotton fabric using stilbene based direct dye has been investigated. The fabric was treated with different concentrations of alkali to optimize the mercerization. The optimum mercerized cotton fabric was irradiated to absorbed doses of 2, 4, 6, 8 and 10 kGy using Cs-137 gamma irradiator. Dyeing was performed using irradiated and un-irradiated cotton with dye solutions. The dyeing parameters such as temperature, time of dyeing, pH of dyeing solutions and salt concentration were optimized. The colour strength values of dyed fabrics were evaluated by comparing irradiated and un-irradiated cotton in CIE Lab system using Spectra flash SF650. Methods suggested by International Standard Organization (ISO) were employed to study the effect of gamma irradiation on the colourfastness properties of dyed fabric. It was found that mercerized and irradiated cotton have not only improved the colour strength but enhanced the rating of fastness properties also.     

High efficiency ultra-deep dyeing of cotton via mercerization and cationization

A potentially environmentally responsible dyeing procedure for ultra-deep shades on cotton was developed using a cationization method in combination with mercerization. The effects of both treatments on dyeing performance and colorfastness properties of cotton fabrics dyed with reactive dyes were analyzed individually and in combination. Both mercerization and cationization have been proved to be effective in increasing the depth of shade on cotton. The colorfastness properties, except colorfastness to wet crocking, of mercerized–cationized cotton fabrics dyed without salt were much better than untreated cotton dyed using a conventional dyeing procedure. Unlike untreated cotton fabrics, the concentration of Na₂CO₃ in the dyeing process of mercerized–cationized cotton fabrics was lowered from 20 to 5 g/L without compromising dye fixation and colorfastness properties. With low concentrations of dyes and Na₂CO₃ and no electrolyte in the dye bath effluent, the dyeing procedure of mercerized–cationized cotton fabrics for ultra-deep shades is potentially a more environmentally benign method than conventional dyeing with reactive dyes.     

Studies on never-dried cotton

The differences in the porous and crystalline structure of cell walls in never-dried and nature-dried cottons have been examined by measurements of dye adsorption and desorption, centrifugal liquid retention, and decrystallization due to swelling in sodium hydroxide. Equilibrium dyeings of these two cottons have been carried out at 50 and 60°C with two direct dyes, Chlorazol Sky Blue FF and Chrysophenine G, and the adsorption isotherms obtained. The dye uptake at limiting saturation is found to be quite large for never-dried cotton as compared to nature-dried cotton, indicating a larger number of sites available to dye molecules in the former sample. However, dyeing parameters such as affinity and differential heat of dyeing are found to have lower values for never-dried cotton. This is attributed to the “frozen” structure of a large amount of water held by never-dried cotton, which retards the adsorption of dye molecules. Studies on retention of liquids (glycerol and water) by cotton by use of centrifugation techniques reveal a larger amount of pore volume in never-dried cotton than in nature-dried cotton. X-Ray studies on decrystallization of cotton by swelling in NaOH indicate that the phase transformation to cellulose II in never-dried cotton is complete at 25% (w/w) concentration of NaOH, whereas under identical swelling conditions about 10% residual, unconverted cellulose I is found in the case of nature-dried cotton. A somewhat similar anomaly is found in the dye desorption measurements. Under conditions when the dye can be completely stripped from nature-dried cotton, the never-dried cotton has been shown to retain about 50% to 80% of the adsorbed dye. These observations are attributed to irreversible pore closure during drying of never-dried cotton. Structural collapse occurring during drying of never-dried cotton, after subjecting it to solvent exchange with a large number of organic liquids, was studied by x-ray diffraction, optical microscopy, and centrifugal liquid retention techniques. It was demonstrated that the structural collapse is proportional to the polarity of the organic solvent employed in the final exchange of never-dried cotton, prior to drying. It is concluded that the structural collapse and the development of inaccessible zones in fiber during drying can be reduced if the water in never-dried cotton is exchanged with a nonpolar solvent.     

Reversible crosslinking in cellulose. VII. Memory effect of the crosslinking medium in the dyeing of crosslinked cotton

Cellulose β-mercaptoethylaminocarboxylate made from unmercerized cotton was partially oxidized in various solvents of different swelling power followed by treatment with excess methyl iodide to yield partially disulfide-crosslinked cotton samples of about the same degrees of crosslinking containing sulfonium groups of about the same contents. The effect of the solvent in crosslinking on the equilibrium and kinetics of dyeing with three dyes (Orange II, Direct Scarlet B, and Direct Sky Blue A) of different molecular size was investigated. The 1:1 ionic bonding was observed at equilibrium between sulfonic acid groups in dye molecules and sulfonium groups in modified cottons in cases of Orange II and Direct Scarlet B. The equilibrium uptake of the largest dye, Direct Sky Blue A, was much influenced by the solvent used in crosslinking; the higher the degree of swelling in crosslinking, the larger the equilibrium uptake. The diffusion rate of Direct Scarlet B was much affected by the solvent used; the higher the degree of swelling, the higher the diffusion rate. The pore structure of the crosslinked cotton was discussed. The crosslinked cotton seemed to have a “memory” of the state at the time of crosslinking and to have a tendency to come back close to that state when placed in a dye bath.     

Improvement of colour strength and colourfastness properties of gamma irradiated cotton using reactive black-5

The dyeing behaviour of gamma irradiated cotton fabric using Reactive Black-5 dye powder has been investigated. The mercerized, bleached and plain weaved cotton fabric was irradiated to different absorbed doses of 100, 200, 300, 400, 500 and 600 Gy using Co-60 gamma irradiator. Dyeing was performed using irradiated and un-irradiated cotton with dye solutions. The dyeing parameters such as temperature of dyeing, time of dyeing and pH of dyeing solutions were optimised. The colour strength values of dyed fabrics were evaluated by comparing irradiated and un-irradiated cotton in CIE Lab system using Spectra flash SF650. Methods suggested by International Standard Organisation (ISO) were employed to study the effect of gamma irradiation on the colourfastness properties of dyed fabric. It is found that gamma irradiated cotton dyed with Reactive Black-5 has not only improved the colour strength but also enhanced the rating of fastness properties.     

Salt-free dyeing of ramie fabric with an amino-terminated hyperbranched polymer

A new amino-terminated hyperbranched polymer (at-HBP) was synthesized, and its salt-free dyeing property on ramie fabric was studied. The structure and molecular weight of at-HBP were established by Fourier transform infrared spectrometer, H nuclear magnetic resonance and gel permeation chromatography. The untreated ramie fabric and modified ramie fabrics were characterized by an X-ray diffraction (XRD) and field emission scanning electron micrograph (FE-SEM). XRD results showed a transformation of the crystalline structure from ramie cellulose I to cellulose II allomorph during mercerization and epichlorohydrin modification, and the crystalline structure of cellulose II was maintained with an obvious crystallinity index increase after at-HBP modification. FE-SEM results confirmed that at-HBP was successfully grafted onto the fabric surface. Dyed with reactive dye C.I. reactive Blue 4, the color strength of the at-HBP-modified fabric was enhanced, even when dyeing was carried out without the electrolyte. The washing and rubbing fastness of the salt-free dyeing of fabrics was also good compared with those obtained by conventional dyeing. The adsorption isotherm of C.I. reactive Blue 4 on modified fabric was examined and found to follow a Langmuir-type adsorption model. The at-HBP modification mechanism of ramie fabric and dyeing mechanism with reactive dye were suggested.     

Direct dyes as molecular sensors to characterize cellulose substrates

Six dyes were selected based on their molecular structure to test theirsuitability as sensors to characterize the fine structure of cellulosesubstrates. Cotton, mercerized cotton and microcrystalline cellulose werechosento represent a variety of pore structures typically encountered in practicalapplications. Internally available surface areas were calculated. It ispostulated that roughly 25% of the Connolly surface areas (CSA) of the sensorsDirect Blue 1, Direct Blue 14, Direct Blue 53, Direct Red 28, and Direct Red 2and 30% of the CSA of Direct Yellow 4 are representative of the space requiredfor the sensor to dock onto cellulose surfaces. Molecular weight of the dyeprobes does not serve as a good indicator of sensor size. Molecular structureisa critical factor to take into account when selecting a probe.     

Mercerized cellulose biocomposites: a study of influence of mercerization on cellulose supramolecular structure, water retention value and tensile properties

In this study the effect of the mercerization degree on the water retention value (WRV) and tensile properties of compression molded sulphite dissolving pulp was evaluated. The pulp was treated with 9, 10, or 11 % aqueous NaOH solution for 1 h before compression molding. To study the time dependence of mercerization the pulp was treated with 12 wt% aqueous NaOH for 1, 6 or 48 h. The cellulose I and II contents of the biocomposites were determined by solid state cross polarization/magic angle spinning carbon 13 nuclear magnetic resonance (CP/MAS ¹³C NMR) spectroscopy. By spectral fitting of the C6 and C1 region the cellulose I and II content, respectively, could be determined. Mercerization decreased the total crystallinity (sum of cellulose I and cellulose II content) and it was not possible to convert all cellulose I to cellulose II in the NaOH range investigated. Neither increased the conversion significantly with 12 wt% NaOH at longer treatment times. The slowdown of the cellulose I conversion was suggested as being the result from the formation of cellulose II as a consequence of coalescence of anti-parallel surfaces of neighboring fibrils (Blackwell et al. in Tappi 61:71–72, 1978; Revol and Goring in J Appl Polym Sci 26:1275–1282, 1981; Okano and Sarko in J Appl Polym Sci 30:325–332, 1985). Compression molding of the partially mercerized dissolving pulps yielded biocomposites with tensile properties that could be correlated to the decrease in cellulose I content in the pulps. Mercerization introduces cellulose II and disordered cellulose and lowered the total crystallinity reflected as higher water sensitivity (higher WRV values) and poorer stiffness of the mercerized biocomposites.     

Chemical cationization of cotton fabric for improved dye uptake

Cotton fabric is usually dyed with reactive dyes. During the dyeing process, a large amount of salt is required to achieve higher exhaustion of the dye from the dyebath onto the fiber. Dyeing of cotton with reactive dyes has a substantial environmental impact due to the discharge of a large volume of highly colored and saline effluents. Chemical cationization allows cotton fibers to be dyed without salt by chemically modifying cellulosic macromolecules to introduce positively charged sites. In this study, cotton fabric was cationized using (3-chloro-2-hydroxylpropyl) trimethyl-ammonium chloride (CHPTAC). Dye uptake was assessed using two reactive dyes, CI Reactive Blue 235 and CI Reactive Blue 19. Dye exhaustion kinetics were determined using a Datacolor-HueMetrix Monitor system. Analysis of variance demonstrated significant effects of CHPTAC concentration and exhaustion time on the percent exhaustion. Color strength at the end of the dyeing cycle was significantly higher for cationized fabrics compared to the control fabric. This work shows that treatment of cotton with CHPTAC enhanced dye uptake properties due to the introduction of cationic sites and resulted in superior dyeing without the addition of salt.     

Cellulose loading and water sorption value as important parameters for the enzymatic hydrolysis of cellulose

The enzymatic hydrolysis of cotton raw cellulose (RC) samples, sieved RC samples through meshes <100 (CS1), 100–200 (C12), 200–400 (C24), mercerized RC samples (M-C), freeze-dried RC (RC-FD) samples, microcrystalline cellulose Avicel, bacterial cellulose (BC), raw sisal pulp and mercerized sisal pulp (S-M) was performed at cellulose-to-cellulase mass ratios of 1,000:1, 699:1, 400:1, 100:1 and 10:1. The index of crystallinity and water sorption values were quantified for all samples. The morphological features were analyzed by means of scanning electron microscopy (SEM). For cellulose-to-cellulase mass ratio of 100:1 and 10:1, the maximum hydrolysis extents of cellulose samples after 24 h reaction could not be correlated with their physical characteristics. However, hydrolyses of samples with large water sorption values were faster than those with lower water sorption values. The hydrolysis efficiency decreased when the cellulose-to-cellulase mass ratio was greater than 400:1; under this condition a remarkable dependence of the hydrolysis yield on the type of cellulosic sample was observed. The water sorption ability could be directly correlated with the hydrolysis extent, except for RC-FD and BC samples, which presented the lowest values. In the former, freeze-drying has led to pore collapse, with concomitant reduction of the amount of adsorbed water. For the latter sample, the densely packed structure made the water sorption slower than in all other samples. Despite of this fact, the presence of nanofibrils on the surface of BC (as detected by SEM) improved the enzyme adsorption, indicating that analysis by complementary techniques should be performed in order to predict the enzymatic hydrolysis efficiency.     

Prediction of low-sensitivity reactive dye recipe in exhaust dyeing influenced by material to liquor ratio and nature of salt

Reactive dyeings were carried out by exhaust method on 100% cotton knits. A trichromatic combination was chosen with only change in blue component. Colorimetric data were produced under controlled dyeing conditions by comparing the color difference between the target shade and resulting shades. Giving a change in liquor ratio and nature of salt the colorimetric data were regenerated again produced the shades. The data will be helpful to predict the low-sensitivity reactive dye recipe, which lead to the concept of right-first-time dyeing. The aim of this research is to help a dyer to select the right recipe. A set of the dye recipes was applied by dyeing with reactive dyes on cotton. Sodium chloride shows best results in terms of dye sensitivity as compared to Glauber's salt at low liquor ratio that is 1:10. Blue BRF in combination with yellow and red shows best result as compared to navy blue BF.     

Diffusion of acid dyes in nylon film in the presence of inorganic salts

The concentration-dependence measured by steady-state permeation and unsteady-state dyeing methods for a system of acid dye C.I.Acid Blue 182–nylon 6 film in the presence of inorganic salts such as NaCl, Na₂SO₄, and K₂SO₄, was analyzed in terms of parallel diffusion with simultaneous multimodal adsorption. It would found that the dyeing process with added NaCl was governed by surface diffusion with two kinds of Langmuir adsorption, whereas with added Na₂SO₄ and K₂SO₄ it was governed by surface diffusion with three kinds of Langmuir adsorption.     

Dye fixation and decolourization of vinyl sulphone reactive dyes by using dicyanidiamide fixer in the presence of ferric chloride

A synthetic polymer was synthesized and used for the improvement of dyeing properties as well as decolorization of textile waste water. Two dyes were selected having anthraquinone based Remazol Blue R and azo based Remazol Red RB. It was observed that the synthetic polymer can be used as fixer for the fixation of dye by crosslinking between dye and fibre, which not only improves the dyeing properties but also helpful to coagulate the colour after dyeing. By single point method the concentrations of synthetic polymer were calculated in residual after dyeing. It was examined that the residual synthetic polymer is helpful in colour removal efficiency by coagulation of polymer with dye to form heavy molecules which settle down and decolorization occurred. Colour removal efficiency was found dependents on pH, concentration of synthetic polymer and inorganic coagulant.     

An evaluation of the dyeing behavior of sol–gel silica doped with direct dyes

A new dyeing process of sol–gel silica doped with direct dyes is investigated for improving color strength (K/S value) and dyeing fastness. Cotton fabrics are dyed in this direct dye silica solution. The results indicate that the K/S value of C.I. Direct Blue 86 and C.I. Direct Red 23 are enhanced by 12.8% and 16.8%, respectively. For C.I. Direct Blue 86, the washing staining fastness is improved by half a grade, and the rubbing fastness and the washing change fastness are enhanced by one grade, respectively. Compared to the fabric fixed with fixing reagent MMF-1, the K/S value is improved by about 23.7% and the wet rubbing fastness and washing change fastness are enhanced by half a grade. The formation of uniform continuous layers on the fiber surface dyed with direct dye silica solution is revealed by video microscope, and the calculated sol–gel weight gain on the fabric is 4.6%.     

Chemical and ultrastructural changes in cotton cellulose induced by laundering and textile use

The textile industry is currently under pressure to decrease environmental load related to both the manufacture and the use of textiles. Material recycling may be one of many ways to accomplish such a decrease. Age-induced property changes in cotton textiles are important to understand in order to facilitate the recycling of cotton textiles. Consequently, this study investigates ultrastructural and chemical changes that take place in the cellulose of cotton sheets over a long time period of use and laundering. Ultrastructural changes were studied using water retention value (WRV), specific surface area measurement, scanning electron microscopy and solid state NMR spectroscopy. Chemical changes through measurement of intrinsic viscosity with and without reductive treatment, molecular mass distribution and carboxylate group content. A substantial decrease in mass average molecular mass from 1,320 to 151 kDa was observed when subjecting the sheets to more than 50 launderings. In contrast, only small differences in WRV, in fibril dimensions and crystallinity estimated using solid state NMR spectra, were observed between sheets laundered 2–4 times and more than 50 times. On one hand, the combination of minor laundering effects of WRV and solid state NMR spectra, together with the large decrease in molecular mass are positive indications for the possibility of recycling cotton into regenerated cellulosic fibres. On the other hand, results show that the specific surface area decreased, which implies that the reactivity of cotton cellulose may decrease during long-term use and laundering.     

The effect of grafting on the dyeability and properties of some modified celluloses

Summary Poly(acrylonitrile) and poly(methyl methacrylate) were grafted onto standard and chemically modified celluloses under various conditions using Ceric IV ion as a catalyst. Purified Chlorazol Sky Blue FF (C. I. Direct Blue 1) was used in dyeing the standard and modified cellulosic fabrics. Chemically modified celluloses were obtained by oxidation and cross-linking with various agents using standard procedures. Generally, grafting lowered the dye affinity, of standard and cross-linked celluloses.With 2 tables     

Interfacial interactions in polymer-layered silicate nanocomposites

Interactions between sodium montmorillonite (Na-MMT) and a variety of probes, some of which are intended to model components of a polyurethane system, have been studied. Particular attention was given to the effect of preadsorbed water on the adsorption behavior of the probes. Flow microcalorimetry (FMC), diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS), and wide-angle X-ray scattering (WAXS) were used to monitor the adsorption process. The probe set included alcohols, amines, ethers, poly(propylene glycol) monobutyl ethers (PPG), and 4-ethylphenyl isocyanate (4-EPI). FMC revealed that the preadsorbed water molecules on undried Na-MMT hindered the adsorption of alcohol and ether probes, but had little effect on the adsorption of amines. Drying of Na-MMT to less than 0.3% w/w H2O led to an increase in heat of adsorption and generally greater retention of the probes. PPG showed strong interaction with Na-MMT due to multipoint adsorption. With dried Na-MMT, WAXS revealed that PPG of molecular weight (MW) 1000 was partly intercalated into the gallery while lower molecular weight PPG (MW 340) did not intercalate the Na-MMT. DRIFTS spectra of 4-EPI adsorbed on undried Na-MMT revealed urea linkages, indicating formation of N,N'-bis(4-ethylphenyl) urea. In contrast, with dried Na-MMT the 4-EPI formed a urethane linkage with hydroxyl groups present at the edges of the silicate platelets.     

Preparation and characterization of cellulose nanofibers from partly mercerized cotton by mixed acid hydrolysis

Cellulose nanofibers with a diameter of 70 nm and lengths of approximately 400 nm were fabricated from partly mercerized cotton fibers by acid hydrolysis. Morphological evolution of the hydrolyzed cotton fibers was investigated by powder X-ray diffraction, Fourier transform infrared analysis and field emission scanning electron microscopy. The XRD results show that the cellulose I was partially transformed into cellulose II by treatment with 15 % NaOH at 150° for 3 h. The crystallinity of this partially mercerized sample was lower than the samples that were converted completely to cellulose II by higher concentrations of NaOH. The intensities of all of the diffraction peaks were noticeably increased with increased hydrolysis time. Fourier transform infrared results revealed that the chemical composition of the remaining nanofibers of cellulose I and II had no observable change after acidic hydrolysis, and there was no difference between the hydrolysis rates for cellulose I or II. The formation of cellulose nanofibers involves three stages: net-like microfibril formation, then short microfibrils and finally nanofibers.     

SPECTRALLY SENSITIZED PHOTOCONDUCTIVITY OF ZINC OXIDE CRYSTALS*

Abstract— Spectral sensitization of photoconductivity was found after coating single crystals with an organic dye in a methanol solution. Similar experiments have been carried out under conditions designed to exclude the influence of solvent and adsorbed gases. The dye was deposited from vapor onto clean crystal surfaces in ultrahigh vacuum and the spectral distribution of the photoconductivity was observed without admission of air. With both methods of dyeing, the quantum yields, referred to the absorbed light, were comparable to the yield in the intrinsic region. Also the influence of a transverse electric field upon surface conductivity before and after dyeing was studied. From the ‘field effect’ it is concluded that the adsorbed dye causes a considerable increase of the density of electronic surface states near the Fermi level.     

Adsorption thermodynamic and kinetic of disperse dye on cotton fiber modified with tolylene diisocyanate derivative

Adsorption thermodynamic and kinetic study of disperse dye on cotton fiber modified with tolylene diisocyanate derivative was carried out under the condition of pH value 6.0 ± 0.2, initial dye concentration 0.01–3.0 g/L and liquor ratio 2,000:1. The result showed the equilibrium adsorption isotherm of disperse dye on modified cotton fiber was Langmuir—Nernst mixed Model and the saturated adsorption capacity of the turning point was 7.1429 mg/g. The calculation of the thermodynamic parameters indicated that the Van der Waals’ forces played a major role between the disperse dye and the modified cotton fiber, and the adsorption of disperse dye on the modified cotton fiber was exothermic process. Compared with the diffusion coefficient and the activation energy of disperse dye on various fibers, the disperse dye diffusion in modified cotton fiber was more difficult than that in original cotton. Meanwhile, it was found that the adsorption kinetics of disperse dye on modified cotton fiber was well agreed with a pseudo second-order kinetic model.