The kinetics and thermodynamics of nylon 6 fiber dyeing with hydrogen peroxide‐glyoxal redox system

Investigations were focused on the kinetics and thermodynamics of nylon 6 fiber dyeing with the hydrogen peroxide‐glyoxal redox system. We tried to understand thoroughly the difference between the new redox and the conventional dyeing system, since the mechanism of redox dyeing is a combination of free radical and ionic dyeing, whereas the conventional system is only ionic. The study consisted of measuring the dyeing transition temperature (T_D), diffusion coefficient (D_T), activation energies of diffusion, dyeing affinity, and the dyeing enthalpy and entropy. From the experimental results, the dyeing transition temperature (T_D) in the redox system is lower than that in the conventional system. But the diffusion coefficient (D_T) in the redox dyeing is larger than that in the conventional dyeing. The dyeing affinity of the free radical dyeing type (redox) is lower than that of the ionic type (conventional). Moreover, from the analysis of thermodynamics of dyeing, the enthalpy is found to be positive (endothermal reaction) in the redox system, but it is negative (exothermal reaction) in the conventional one. The entropy is also found to behave similarly, i.e. positive in the redox system, but negative in the conventional dyeing. Finally, the dyeing saturation value in the redox dyeing system is found to be higher than that in conventional dyeing. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 2105–2114, 2000     

Effect of microencapsulation on dyeing behaviors of disperse dyes without auxiliary solubilization

Microencapsulated disperse dye can be used to dye hydrophobic fabric in the absence of auxiliaries and without reduction clearing. However, little available information for dyeing practice is provided with respect to the effect of microencapsulation on the dyeing behaviors of disperse dyes. In this research, disperse dyes were microencapsulated under different conditions. The dyeing behaviors and dyeing kinetic parameters of microencapsulated disperse dye on PET fiber, e.g., dyeing curves, build up properties, equilibrium adsorption capacity C_∞, dyeing rate constant K, half dyeing time t_1/2, and diffusion coefficient D were investigated without auxiliary solubilization and compared with those of commercial disperse dyes with auxiliary solubilization. The results show that the dyeing behaviors of disperse dye are influenced greatly by microencapsulation. The diffusion of disperse dyes from microcapsule onto fibers can be adjusted by the reactivity of shell materials and mass ratios of core to shell. The disparity of diffusibility between two disperse dyes can be reduced by microencapsulation. In addition, the microencapsulation improves the utilization of disperse dyes due to no auxiliary solubilization. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Studies on dyeing and structural behavior of chemically treated polyester yarns

The dyeing behavior of poly(ethylene terephthalate) based flat, high twist, and spun yarns pretreated with trichloroacetic acid–methylene chloride (TCAMC) reagent was studied. Disperse dyes having two different energy levels were employed for the dyeing work. The effect of time, temperature, and dye diffusion transition temperature (T_D) on dye uptake was analyzed. A considerable increase in equilibrium dye uptake and decrease in T_D of all the treated yarns were observed. The variation in dye diffusion behavior of higher and lower molecular weight dyes and the difficulties encountered in calculating the diffusion coefficient of the dyes are discussed. The structural and morphological changes effected by the pretreatment were also investigated using XRD and SEM, respectively. The increase in lateral order of the treated yarns was noted. The possible reason for an unusual relationship between the increase in lateral order and increase in dye uptake was explained. The cross-sectional shape and swelling and the smoothening out of the fiber surface were evidence by SEM. © 1996 John Wiley & Sons, Inc.     

Non-steady state estimation of biodegradability of dyeing wastewater using respirometer

Dyeing wastewater is notorious for its non-readily-biodegradability because it contains various kinds of refractory chemicals. To set up a strategy for controlling the dyeing wastewater discharged into conventional wastewater treatment plants, obtaining bio-kinetic information such as maximum specific growth rate (μ _max ) and half saturation constant (K _s ) should first be done. To estimate the biodegradability of the dyeing wastewater, bio-kinetic constants of the artificially formulated dyeing wastewater containing 33 different dyes and auxiliaries were determined by using a respirometer. Activated sludge acclimated to the artificial dyeing wastewater was inoculated to the respirometer and the bio-kinetic constants were determined from oxygen uptake data. The μ _max was found to 0.06 hr⁻¹, which is 3 to 15 times smaller than that of the typical activated sludge for sewage treatment. The K _s was found to 210 mg/L, which was 3.5 to 21 times higher than that of the normal activated sludge.     

Carrier‐free dyeing of radiation‐grafted polyester fabrics with disperse dyes

Carrier‐free dyeing of radiation‐grafted polyester fabrics with disperse red dye was studied in the temperature range 283–363 K. 1‐vinyl 2‐pyrrolidone (NVP), acrylic acid (AA) or their mixture was used to graft poly(ethylene terephthalate) (PET) fabric. The effects of pH of the dye solution, graft yield (GY), dyeing time (t), dye concentration (C), and dyeing temperature (T) on the colour difference (CD) of PET fabric were studied. The best dyeing condition was achieved at pH 5.5. CD increases linearly with the increase in GY, with slopes depending on the type of grafted copolymer. CD increased rapidly as the dyeing time increased; this was followed by a relatively slow dyeing rate within a few minutes. The initial dyeing rate (R) was found to increase with an increase in C and T. The dyeing rates for all grafted samples followed 0.35‐order kinetics and are temperature‐independent. Average activation energy 9.26 kJ mol^?1 is calculated for the dyeing process and is independent of the fabric treatment. Pre‐exponential rate constants 1976, 1839, and 1579 (CD/GY) s^?1 were calculated for dyeing PET samples grafted with AA/NVP mixture, NVP and AA, respectively, while 1074 CD s^?1 was evaluated for carrier dyeing of ungrafted fabric. Analysis of the kinetic parameters and the dyeing mechanism revealed that dyeing PET fabric was diffusion‐controlled. Grafting PET fabric improved significantly the dyeing affinity of the DR dye over ungrafted samples dyed in solutions containing a carrier. Copyright © 2005 Society of Chemical Industry     

A novel strategy for realising environmentally friendly pigment foam dyeing using polyoxyethylene ether surfactant C14EO5 as a foam controller

Development of an environmentally friendly pigment dyeing process with excellent colour depth and levelness is an effective strategy for solving pollution problems in traditional dyeing. A functional polyoxyethylene ether nonionic surfactant, tetradecyl alcohol polyoxyethylene ether with an EO chain length of 5 (C₁₄EO₅), was used as a foam controller, namely a foaming agent and foam stabiliser, in the pigment foam dyeing process. The foamability and the foam stability of C₁₄EO₅ were tunable by adjusting its concentration. The foaming ratio and the foam half-life of C₁₄EO₅ were 5.22 and 32.21 min, respectively, at a concentration of 8 wt%. The addition of pigment dispersion (ranging from 1 to 6 wt%) slightly affected the foaming ratio and the foam half-life owing to the interplay of increased viscosity and pigment particle destabilisation. After the influences of binder on foam properties of C₁₄EO₅ were investigated, the concentration of binder and the stirring time for foaming were determined as 15 wt% and 7 min respectively. Owing to the stable foaming ratio and foam half-life of the pigment foam dyeing dispersion, the colour depth of dyed cotton fabric was tailored solely by changing the dosage of pigment dispersion. Furthermore, the dyed cotton fabric showed not only a high K/S value but also perfect colour levelness and fastness. These results demonstrate that the pigment foam dyeing process with a foam controller, C₁₄EO₅, reduces chemical and water consumptions, as well as improving the colour depth and levelness. This represents a significant step forward as regards environmentally friendly pigment dyeing.     

Disperse dyeing of polyester fibers: Kinetic and equilibrium study

The effect of temperature on the dyeing rate constant k, diffusion coefficient D, and time of half‐dyeing t_1/2 was evaluated for the dyeing of polyester fibers with two disperse dyes, an azo and an anthraquinone dye. Activation energies of diffusion E were calculated. The polyester dyeing equilibrium was also studied and the partition coefficient K and standard affinity Δμ° at various temperatures were determined for the anthraquinone dye. Standard enthalpy ΔH° and standard entropy ΔS° of dyeing were also obtained. The same equilibrium parameters were not obtained for the azo dye because of its dyeing behavior. A similar kinetic and equilibrium study was made for the pure azo and anthraquinone compounds free from the dispersing agents present in the commercial dyes and the results are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 123–128, 2002     

Dyeing mechanism and model of nylon 6 fiber dyeing in low‐temperature hydrogen peroxide–glyoxal redox system

This article reports the results of a study of nylon 6 fiber dyed in a low‐temperature hydrogen peroxide–glyoxal redox system. It was expected that the dyed fiber would have better dye fastness and higher economic value than would conventional fiber. In addition, this article presents the proposed mechanism for and model of a free‐radical dyeing system as well as a derived theoretical equation. From the experimental results, it was found that formation of covalent bonds by the coupling of the dye and the fiber radical in free‐radical dyeing was only 25%–40%, whereas with the conventional type of ionic dyeing, it was almost 60%–75%. Because the initiation efficiency of free‐radical formation is affected by many factors, such as the pH of the dye bath and the concentrations of the oxidant and reductant, the aims of this study were to investigate the formation of free radicals and the effects on dye uptake of the concentrations of dye, oxidant, and reductant and of the fiber amine end group. In addition, the dyeing properties of dyed fiber were investigated, and the dyeing order and rate constant of the rate equation were evaluated from the experimental data. From the experimental results, the following conclusions were drawn. (1) The hydrogen peroxide–glyoxal redox system produced many free radicals in the dye bath as temperature reached 70°C. (2) The amine end group in the nylon fiber was the main site of ionic and covalent bonding between nylon 6 fiber and dye. (3) The proposed model of free‐radical dyeing showed, from the fit of the experimental data into the equation and the evaluation of the equation parameters, that the order fit the theoretical value well, with the rate constant dependent on the dyeing conditions; at pH = 3, it could match the equation's best (rate equation of the proposed model: d[D]_R/dt = k_A[GO]¹[H₂O]^m[D]^1/2[F]^1/2). (4) The optimum dyeing conditions in the hydrogen peroxide–glyoxal redox system were: [H₂O₂] = 0.15–0.20M, [glyoxal] = 0.07–0.10M, pH = 3, dyeing temperature = 70°C, and dyeing time = 45–50 min. (5) The redox dyeing system had better dye fastness than did the conventional system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4197–4207, 2006     

Disperse dyeing of polyester fibers: Kinetic and equilibrium study

The effect of temperature on the dyeing rate constant k, diffusion coefficient D, time of half‐dyeing t_1/2 was evaluated for the dyeing of polyester fibers with two disperse dyes, an azo and an anthraquinone dye. Activation energies of diffusion E were calculated. The polyester dyeing equilibrium was also studied and the partition coefficient K and standard affinity Δμ° at various temperatures were determined for the anthraquinone dye. Standard enthalpy ΔH° and standard entropy ΔS° of dyeing were also obtained. The same equilibrium parameters were not obtained for the azo dye because of its dyeing behavior. A similar kinetic and equilibrium study was made for the pure azo and anthraquinone compounds free from the dispersing agents present in the commercial dyes and the results are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2785–2790, 2002; DOI 10.1002/app.10254     

Diffusion of dyes in polyester fibers. III. Time delay in establishment of the equilibrium concentration of dye at fiber surface

In the dyeing process of the copolyester fiber Dilana with the disperse dye Synthene Scarlet P3GL, a deviation from the simple model of Fickian sorption occurs. It manifests itself as a time delay in establishment of the equilibrium dye concentration at the fiber surface. As has been stated, the variation of C_s (the surface dye concentration) with time of dyeing fits the equation; C_s = C_∞ (1? e^?βt). Regarding the relation of C_s to t, the diffusion coefficient of the dye in the studied fiber has been calculated by the theoretical equation reported in Crank's monograph. It has been proved that the experimental data on kinetics of dyeing the fiber Dilana with Synthene Scarlet P3GL fit considerably better the tested equation than the classical Hill's equation.     

The effect of phenol and biphenyl on the properties of poly(ethylene terephthalate) film

Evidence is presented which justifies the use of the dyeing transition temperature (T_D) instead of the glass transition temperature (T_g) as a reference temperature when using the WLF equation to describe the carrier dyeing of polyester film. Changes in the properties of the substrate caused by the effect of “carriers” on the molecular structure of the polymer have also been detected and a connection between the location of T_D and chain folding is suggested from IR measurements.     

The carrier dyeing of synthetic fibers

The mode of action of carriers in augmenting the rate of dyeing of disperse dyes with acrylic and polyester fibers is discussed in terms of the plasticizing action of the carrier. It is shown that the effectiveness of a carrier is determined by its ability to reduce the glass transition temperature of the fiber and not by the fiber swelling. The rate of dyeing as measured by the diffusion coefficient of the dye is shown to be uniquely related to the difference between the dyeing temperature and the glass transition temperature (T – T_g). In the light of these results, some aspects of carrier action in dyeing from perchlorethylene are discussed. Treatment of polyester fibers with carrier also increases crystallinity. Changes in diffusion for a series of copolyesters have been correlated with the long spacing obtained from small angle X-ray scattering (SAXS).     

The efficiency of various carriers on the dyeing of an acrylic fibre

The effects of various carriers on the reduction of the glass transition temperature (T_g) and the dyeing transition temperature (T_d) of an acrylic fibre in a cationic dyeing system have been investigated. Linear relationships were found between the concentration of carriers in the fibre and the reduction of the T_g and the T_d of the fibre. The efficiency of various carriers in reducing the T_g and the T_d, when compared in terms of the molar concentrations of the carriers in the fibre, was found to be similar, regardless of the carriers used.     

A significant approach to dye cotton in supercritical carbon dioxide with fluorotriazine reactive dyes

A series of fluorotriazine reactive dyes have been synthesized and applied to dye cotton in supercritical carbon dioxide (scCO₂) with good dyeing results. The pieces of cotton to be dyed were previously presoaked in a protic solvent and cosolvents were applied during dyeing. The colour strength of the dyeings was evaluated by K/S measurements. The K/S values achieved on cotton dyed were up to 35.8 ± 4.2. Even after the cotton was subjected to a Shoxlet extraction at 358 K for 1 h, a maximum K/S value of 20.2 ± 1.8 was measured. The percentage of dye molecules chemically fixed to the cotton was on average 85%. The excellent reactivity of fluorotriazines allowed a reduction of 3 h on the dyeing time. It is noticeable that a dye concentration of 10% on weight of the fibre (owf) can be applied to dye cotton with fluorotriazines, since no damage of the cotton fibres occurred, as observed for the chlorotriazines at this high dye concentration.Dyes with fluorotriazine as reactive group were found to be the most preferable dyes for dyeing cotton in scCO₂, as they were able to exceed the limitation of the reaction with the cotton.     

Redox-initiated graft copolymerization onto wool with thiourea as reductant. IV. Grafting of vinyl sulfone dyes onto wool using thiourea–H2O2 redox system

Wool samples were dyed with a vinyl sulfone dye in the presence of thiourea and H₂O₂ under a variety of conditions. Increasing the H₂O₂ concentration from 2.5 mmole/l. to 20 mmole/l. caused a significant enhancement in the rate of the dyeing, whereas increasing the thiourea concentration from 1.25 mmole/l. to 10 mmole/l. brought about an increase in the rate of dyeing. Further increase in the thiourea concentration (i.e., up to 15 mmole/l.) caused a significant decrease in the rate of dyeing. Raising the dyeing bath temperature from 30°C to 70°C accelerated appreciably the rate of dye uptake. With respect to dye concentration, complete exhaustion occurred at dye concentrations of 0.5% and 1% (owf) when dyeing was performed at 70°C and pH 6 over a duration of 2 hr. This contrasts with 90% and 55% exhaustion for dye concentrations of 3% and 5% (owf), respectively. The rate of dyeing obtained at different pH's follows the order pH 2 < pH 4 < pH 6 < pH 8. A dye fixation of approximately 68%, 64%, and 50% could be achieved at pH 4, 6, and 8, respectively, if dyeing was performed at 70°C for 2 hr in a bath containing a dye concentration of 3% (owf) in the presence of thiourea (10 mmole/l.) and H₂O₂ (15 mmole/l.). The mechanism of dyeing is believed to be grafting by vinyl addition to wool radical formed under the influence of the decomposition products of thiourea and H₂O₂. Evidence of this mechanism is presented.     

Molecular Mechanisms of Disperse Dyeing of Polyester and Nylon Fibres

The kinetics of the dyeing of polyester fibres with disperse dyes have previously been discussed in terms of a model in which the only forces of interaction between dye and polymer are those that give rise to mutual solubility. The rate and extent of dyeing depend on the size and shape of the dye molecules and the detailed structure of the fibre. The concentration profiles of dye within single filaments of polyesters and nylons have now been determined by a new method termed ‘optical sectioning’, in which an image of a filament is scanned by a narrow slit. The dye distributions are found by comparing experimental transmission values with those calculated by a computer for a model system in which various parameters can be adjusted. For the polyester-dye systems the rate constant of transfer of dye from dyebath to fibre (k₁) was the same as the rate constant of diffusion away from the interface (k₂). Some nylon-dye systems, on the other hand, behaved as if k₂ = k₁, whereas others behaved initially as if k₁ = k₂ but later as if k₂ > k₁. Apparent diffusion coefficients were also derived from sorption measurements and were found to fall as the dye concentration in the fibre increased. Measurement of the orientation of the dye molecules by optical dichroism showed that the dye molecules entering the filaments late in the dyeing process were more highly orientated than the earlier ones. The decrease in diffusion coefficient has been interpreted in terms of the observed higher orientation, as resulting from a greater entropy of activation in the diffusion process.     

Poly(urea-urethane) polymers with multi-functional properties

Polyurea-urethanes with multifunctional properties were synthesized by reacting 4,4′-diphenylmethane disocyanate (MDI) with a two diol mixture of polytetramethylene glycol (PTMG (1000, 2000) and biocidal quaternary ammonium monomer ((N-benzyl-N-dodecyl-N-bis2-hydroxyethyl) ammonium chloride (BDAC)), and extended with N-(2-hydroxyethyl) ethylene diamine (HEDA) to form PU polymers. The PU polymer was then grafted with a disperse dye via a coupling agent of epichlorohydrin to form a dye grafted polyurethane with biocidal and covalent bond dyeing properties. In consideration of the mechanical properties, it is found that both the modulus and the strength of the dye grafted PU polymer films are lower than those of pure PU polymers due to the bulkiness of their dye molecules. For thermal properties, the dye grafted PU polymers exhibit higher T_gh than those without dye molecules. However,neither the T_gs nor the T_ms vary in the presence of BDAC or dye molecules, but they are changed with various chain lengths of the soft segment. For dyeing properties, the effective dyeing efficiency of dye grafted PU is over 85%. Moreover, the dye grafted PU polymers exhibit lower dye migration (M_p%) than those of simple mixtures of PU and dyestuff, and they show a higher grade of color fastness when exposed to light. In the shake method of antibacterial testing, the modified PU polymers exhibit a long lasting biocidal activity.     

Effects of additives on the dyeing of cotton yarn with the aqueous extract of Combretum latifolium Blume stems

Flavonoid constituents from the aqueous extract of the stems of Combretum latifolium Blume sourced in Thailand have potential use as dyestuffs for cotton dyeing. In an effort to improve current natural dyeing methods with this extract, further aspects of the process were studied. It was found that, before equilibrium was reached, an increase in temperature led to an increase in dye adsorption rate of the extract; the initial rate and extent of dye adsorption was further increased by the addition of sodium chloride to the dyebath. In addition, cotton yarn pretreated with a chitosan solution (with and without a crosslinking glyoxal solution), followed by dyeing with C. latifolium extract, provided better depth of shade and also gave better fastness to light and washing than the untreated cotton yarn. Post‐mordanting cotton yarn with a biomordant solution from Memecylon scutellatum leaves also gave good light and wash fastness of the resulting dyed cotton, comparable with the dyeing results with the less environmentally friendly alum as a mordant.     

Modified polyurethane with improvement of acid dye dyeability

This article concerns the modification of polyurethane using polyamide 6,6 prepolymer to improve the dyeability properties of the polyurethane copolymer with acid dye. First, the carboxyl‐terminated polyamide 6,6 prepolymer was synthesized from adipic acid and 1,6‐diaminohexane. The isocyanate‐terminated polyurethane prepolymer was also synthesized from polytetramethylene glycol and 4,4′‐diphenylmethane diisocyanate in N,N‐dimethylformamide. The polyurethane prepolymer was then extended with a mixture of 1,4‐butanediol and the polyamide 6,6 prepolymer (molar ratios of 1,4‐butanediol to prepolymer being 100%, 75%, 50%, and 25%, respectively). Finally, the poly(urethane–amide) copolymers were dyed with acid dyes. The chemical, physical, and the dyeing properties of the poly(urethane–amide) coploymers are discussed. From the experimental results, it is found that the inherent viscosity of poly(urethane–amide) coploymers is increased with the increasing amount of polyamide content. The structure is proven by infrared spectra, which exhibits the absorption peaks of urethane and amide groups as we expected. From the differential scanning calorimetry measurements, it is found that the poly(urethane–amide) coploymers have two‐phase structures and good phase separation. There are four transition temperatures (T_gs, T_gh, T_ms, and T_mh), but only those copolymers in PTMG 2,000 series possess T_ms. Moreover, the T_gs is found to change with the length of soft segment, and the T_gh is increased with the increasing amount of polyamide content. Also, the dyed copolymers exhibit higher T_gh than those without dyeing of dye molecule, but the T_gs is not obviously changed. For mechanical properties, it is indicated that both the modulus and the strength of the coploymers are higher than those of unmodified polyurethane, but they are lowered after being dyed with dye molecule due to further separation of intermolecular distance of the dyed polyurethanes. For dye uptake in dyeing properties, it is found to increase with increasing amount of polyamide content. For dye fastness, the dyed copolymers exhibit higher grade of water fastness than that of unmodified polyurethane. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1397–1404, 2003     

Extraction of polyphenolic substances from bark as natural colorants for wool dyeing

In Europe, considerable amounts of bark are available from wood‐processing industries such as forestry and timber production. Polyphenolic components can be collected by hot water extraction. The extracted compounds can then be applied as colorants in textile dyeing operations. In this study, a comparative assessment of four different tree species with regard to their colouristic potential for wool dyeing was performed. Aqueous extracts from alder, ash tree, spruce and oak bark were prepared and analysed for their total phenolic content and ultraviolet (UV) absorption at 360–370 nm. The extracts were used for meta‐mordant dyeing by adding iron sulphate mordant (FeSO₄ × 7H₂O). For comparison, iron salt‐based dye lakes were prepared and used in dyeing experiments. For each tree species, a specific correlation between the total phenolic content of the dyebath and the colour depth in terms of K/S and CIELab coordinates was observed, both for the aqueous extracts and the dye lakes. Based on this relationship, standardisation and quality control of raw materials and dye lakes can be installed as important stages in the industrialisation of natural colorants from bark. The preparation of concentrated dye lakes permits formation of a concentrated colorant as dye product, which then can be standardised and delivered to textile dyehouses, similar to synthetic dyes. The preparation of dye lakes offers a relevant route towards achieving the commercialisation of bark extracts as natural colorants.