Effect of some aromatic hydroxy sulphonic acids on uptake of acid dyes by nylon 6

The major constituents of a synthetic tanning agent for leather, prepared from the condensation of a naphthol sulphonic acid with formaldehyde, have been separately synthesised and have been shown to be of low molecular weight. The effect of these ‘syntan components’ on the uptake of four acid dyes by nylon 6 has been studied as has the desorption of the agents during the uptake of dye. Although the components have only a minor effect on the rate at which dye is adsorbed by the fibre, they reduce the extent to which dye is taken up at equilibrium. The restraining effect observed is governed by the affinity of both dye and agent. It is concluded that unlike commercial syntans which are available for the aftertreatment of dyed nylon, the products studied diffuse readily into the polymer matrix and, after application to nylon, are not held firmly at the fibre surface.     

Fatigue and environmental resistance of polyester and nylon fibers

The fatigue resistance of individual synthetic fibers can govern the performance of complex fiber assemblies such as tire cord and marine rope under certain loading conditions. This paper explores the relative performance of polyester and nylon 6,6 fibers and yarns, both dry and in aqueous solutions, primarily synthetic seawater. Fiber failure over a range of loading conditions and frequencies was found to occur at a critical cumulative strain, governed by a creep rupture process; the cyclic lifetime for both fibers is predictable using a simple creep rupture based theory. Polyester is more resistant to creep rupture, and consequently outperforms nylon 6,6 in cyclic fatigue. The advantage of polyester is considerably greater in aqueous solutions, where the performance of the nylon is diminished. Other comparisons indicate that the particular polyester fibers studied have higher stiffness and strength, lower strain to failure, and much lower hysteresis energy absorption compared with the nylon. The actual fatigue performance of complex fiber assemblies such as ropes is also limited under many conditions by factors not present in single fiber or yarn fatigue, including hysteric heating and internal and external abrasion.     

Laser scanning confocal microscope characterization of dye diffusion in nylon 6 fibers treated with atmospheric pressure plasmas

The effect of atmospheric pressure plasma treatment on wettability and dyeability of nylon 6 fibers is investigated. The plasma treatments resulted in an average of 10°–20° decrease in the advancing contact angle and 20°–30° decrease in the receding contact angle. An increased dye diffusion rate of nylon 6 fibers was observed using laser scanning confocal microscope (LSCM). Scanning electron microscope confirmed that the fiber surfaces were roughened, and X‐ray photoelectron spectroscopy showed that the polar groups on the fiber surfaces increased after the plasma treatments. As the plasma treatment time increased, a greater degree of etching was achieved and more polar groups such as hydroxyl and carboxyl groups produced on the surfaces of the nylon 6 fibers, leading to a better wettability and thus a better dyeability of the fiber. This study proved that LSCM may be effectively used in detecting the change of dye diffusion rate in nylon fibers treated with plasmas and the mounting medium should have a close refractive index as the fiber to avoid distortion of the fiber cross section image. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The adsorption of a commercial stainblocker on nylon 6.6

The adsorption of a commercial stainblocker onto nylon 6.6 fibers of 45 amino end group (AEG), and also 70 AEG, was found to increase with decreasing application pH, indicating that ion–ion interaction contributed to stainblocker–fiber substantivity. Uptake of the stainblocker also increased with increasing application temperature, which is attributable to the higher kinetic energy of the stainblocker molecules and the greater extent of the fiber‐swelling operative at the higher temperatures. Adsorption of the stainblocker on to 45 AEG fiber increased with decreasing liquor ratio, possibly as a result of stainblocker aggregation, but in the case of 70 AEG nylon fiber uptake, slightly decreased with decreasing liquor ratio. From the finding that uptake of the stainblocker onto undyed 45 AEG and 70 AEG nylon 6.6 followed a Brunauer–Emmett–Teller mechanism, it was postulated that adsorption involves the formation of multilayers and that forces other than ion–ion contribute toward stainblocker–fiber interaction. This postulate gained support from the observation that although the presence of 1% omf dye on the two types of fiber reduced the extent of stainblocker uptake, the mechanism of stainblocker adsorption onto both substrates was unaffected. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3062–3068, 2000     

Ultrasonic‐assisted dyeing: II. Nylon fibre structure and comparative dyeing rate with reactive dyes

Comparative dyeing kinetics of nylon‐6 fibre with different reactive dyes using conventional and ultrasonic conditions are presented. The time/dye‐uptake isotherms are revealing the enhanced dye‐uptake in the second phase of dyeing (diffusion phase). The data of dyeing rate fit well with the integrated form of the first‐order rate equation and values of dyeing rate constant and half‐time of dyeing are discussed. Ultrasonic efficiency in accelerating the dyeing rate relative to conventional heating was examined for all dyes used to show that ultrasonics are most effective for a dyeing system which has difficulty in achieving high dye‐uptake. To clarify the role of fibre fine structure and whether it is affected during dyeing with ultrasonic waves, time‐dependent ultrasonic pre‐treatment of nylon‐6 fibres and its effect on the colour strength obtained is presented. X‐ray diffraction studies on nylon‐6 fibres conventionally and ultrasonically pre‐treated have shown that the percentage of fibre crystallinity has become higher in ultrasonically treated fibre in comparison with that of conventionally treated. Although the increased crystallinity of the fibre, which occurs simultaneously during the ultrasonic dyeing process, would retard dye uptake, it seems that the enhanced effect of power ultrasonic is high enough to overcome this side‐effect on the fibre. © 2003 Society of Chemical Industry     

Creep behavior of nylon fiber-reinforced asphalt concrete

This study aims to investigate the permanent deformation behavior of asphalt concrete reinforced by nylon fibers. Nylon fibers (12 mm length) have been added to a typical asphalt concrete at different percentages of 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3% (based on total weight of mixture), and the permanent deformation behavior of the mixtures have been investigated by dynamic creep tests at different stress levels of 200 and 400 kPa, and different temperatures of 40, 50, and 60 °C on the mixtures. A three-stage model (developed by Zhou et al.) has been used for modeling the creep curve of the mixtures and determining the flow number and creep strain slope of the mixtures, which are used to describe the permanent deformation of asphaltic mixtures. The parameters of the models were determined in MATLAB using an algorithm established by Zhou et al. The results showed that the mixture reinforced by 0.1% of nylon fibers has the highest resistance to permanent deformation. The three-stage model was well fitted with the dynamic creep test results of the mixtures. The results also showed that the mixture containing 0.1% of nylon fibers has the lowest creep strain slope and the highest flow number, indicating that this mixture has the highest resistance to permanent deformation.     

Relations between viscoelastic parameters of hydrophobic fiber and dyeing with disperse dyes

Experimental evidence is presented to show that the kinetics of dyeing of hydrophobic fibers with disperse dyes can be represented by an equation of the same form as the well-known equation giving creep in fibers. A mechanism is proposed whereby one can regard the dye uptake in the fiber at a constant temperature as a viscoelastic phenomenon in the dye-polymer system. A comparison of these two equations enables the dyeing constants to be interpreted in terms of the viscoelastic parameters of the system. It is also possible to find the upper bounds for the dyeing rate and a condition for rapid dyeing on the same basis.     

The Effect of Buffer Systems on the Uptake of Acid Dyes by Wool and Nylon

For the measurement of adsorption of acid dyes by wool and nylon a dyebath pH of 4 can be achieved either by the use of aqueous solutions of acids, e.g. formic acetic or sulphuric acid or by the use of standard buffer solutions, e.g. acetic acid/sodium or ammonium acetate, phenylacetic acid/potassium phenylacetate or potassium hydrogen phthalate. In this work, wool yarn and nylon 6 filament have been dyed from aqueous solutions of C.I. Acid Reds 1 and 41 at a pH value of approximately 4.2 in the presence of either aqueous acetic acid or a selected pH 4 buffer. The effect of each buffer system on the rate of adsorption of each dye by wool and nylon fibres has thus been studied. It was found that, in some cases, the buffer system had a significant effect on the rate and extent of dye uptake. The use of potassium hydrogen phthalate, a primary pH standard, to produce a dyebath pH of 4.2 gave a greatly reduced adsorption of the two dyes by both fibres.     

Dyeing of nylon 6 and silk fabrics with a model disulphide bis(ethylsulphone) reactive disperse dye

The synthesis of a new reactive disperse dye containing the disulphide bis(ethylsulphone) group is described. The dye has been applied to nylon 6 and silk fabrics at a variety of pH and temperature conditions. Optimum dye exhaustion and fixation were achieved at pH 8 and 130 °C. The results of dyeings on both substrates indicate that the model disulphide bis(ethylsulphone) reactive disperse dye shows a higher degree of exhaustion and fixation on silk than on nylon 6. The fastness and levelling properties on both fabrics were good.     

Dyeing properties of oxygen low-temperature plasma-treated wool and nylon 6 fibres with acid and basic dyes

Wool and nylon 6 fibres treated with oxygen low-temperature plasma were dyed with acid and basic dyes. Despite the increase of electronegativity of the fibre surface caused by the plasma treatment, the rate of dyeing of wool was increased with both dyes, while that of nylon 6 was decreased with the acid dye and increased with the basic dye.     

Effect of a synthetic tanning agent on the diffusin properties of an acid dye in nylon 6

The diffusion coefficients of an acid dye in nylon 6 polymer hav been measured using two different techniques, one based on the rate at which the fiber absorbs the dyestuff and the other employing the rate of transport of dye through a nylon film. Both of these methods yield diffusion coefficients of similar magnitude. The effect of a synthetic tanning treatment on the diffusion coefficients has been studied and it has been shown that a significant reduction in the diffusion coefficient is only obtained from data based on adsorption measurements. It is concluded that the decrease of rate of dye uptake caused by the presence of the syntan is due mainly to the prevention of initial dye adsorption rather than electrical repulsion or steric effects proposed in earlier studies. These results also highlight the dangers in using adsorption studies as a method for determining diffusion parameters.     

Dyeing Kinetics of an Acid Dye in a Nylon Film

The dyeing kinetics of an acid dye (C. I. Acid Blue 182) in a nylon 6 substrate was investigated using partition–cell and film–roil methods. The concentration dependence of the diffusion coefficient of acid dye in the nylon film was derived from both methods and compared with a prediction based on diffusion together with adsorption equilibrium established instantaneously between mobile and immobilised dye molecules in pores. These two sets of experimental results were found to be incompatible with each other. It was deduced that two kinds of region exist in the nylon, one being a region available for rapid penetration and the other, connected to it and formed by slow relaxation, a region of poor penetration.     

Transport of acid dye in nylon and concentration dependence of the diffusion coefficient

The dyeing kinetics of an acid dye (C. I. Acid Blue 40) in a nylon 6 film were investigated using partition-cell and film-roll methods at 80°C and pHs 2.3 and 3.05. The concentration dependence of diffusion coefficient of the dye in the nylon substrate measured by both methods was interpreted in terms of parallel diffusion with biomodel sorption of the Nernst and Langmuir modes. As the concentration of dye increases, the transport of dye inside the nylon film becomes dominated by pore diffusion and surface diffusion of sorbed Nernst populations.     

Creep behavior of glass‐fiber‐reinforced nylon 6 products

The creep properties, that is, the velocity constant, activation energy, stress index, and time index, of a test piece (TP) cut from a glass‐fiber‐reinforced nylon 6 product were successfully determined by a compression creep test. In the determination of the creep properties, the experimental creep curves for the TP were fitted by finite element analysis (FEA). Fiber‐reinforced nylon 6 beams with different fiber orientations were also prepared, and their creep properties were successfully determined by a combination of the bending creep test and the corresponding analysis. The creep behavior of the press‐fit component composed of a metal collar and a fiber‐reinforced nylon 6 product was predicted by FEA with the determined creep properties of the TP. The predicted retention forces were in good agreement with the experimental ones. The effects of the fiber orientation on the long‐term reliability of the press‐fit component are also discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology and crystallization behavior of nylon 6‐clay/neat nylon 6 bicomponent nanocomposite fibers

Nylon 6‐clay hybrid/neat nylon 6, sheath/core bicomponent nanocomposite fibers containing 4 wt % of clay in sheath section, were melt spun at different take‐up speeds. Their molecular orientation and crystalline structure were compared to those of neat nylon 6 fibers. Moreover, the morphology of the bicomponent fibers and dispersion of clay within the fibers were analyzed using scanning electron microscopy and transmission electron microscopy (TEM), respectively. Birefringence measurements showed that the orientation development in sheath part was reasonably high while core part showed negligibly low birefringence. Results of differential scanning calorimetry showed that crystallinity of bicomponent fibers was lower than that of neat nylon 6 fibers. The peaks of γ‐crystalline form were observed in the wide‐angle X‐ray diffraction of bicomponent and neat nylon 6 fibers in the whole take‐up speed, while α‐crystalline form started to appear at high speeds in bicomponent fibers. TEM micrographs revealed that the clay platelets were individually and evenly dispersed in the nylon 6 matrix. The neat nylon 6 fibers had a smooth surface while striped pattern was observed on the surface of bicomponent fibers containing clay. This was speculated to be due to thermal shrinkage of the core part after solidification of the sheath part in the spin‐line. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39996.     

A similarity criterion of the optimal process in melt spinning

Experimental and simulation studies of optimization of the melt spinning process were carried out for nylon 6 fibers. The experiment and process simulation demonstrated that one criterion that can be applied in scaling up an optimized melt spinning process is to achieve the similar real time history of temperature and deformation rate in the spinway. Some aspects of the experiments and process simulation are discussed, together with the results of real time history analysis for a case of nylon 6 spinning.     

Transport of Acid Dye in Nylon Film

The results of both steady-state permeation and non-steady-state dyeing experiments over a wide range of dye concentrations for a system consisting of an acid dye (C.I. Acid Blue 182) and a nylon 6 film were analysed on the basis of surface diffusion with simultaneous multimodal adsorption. The concentration dependence of the diffusion coefficient of the dye in the nylon film can be explained by surface diffusion incorporating one Nernst-type and two Langmuir-type adsorption mechanisms except when high concentrations of dye are applied. The concentration dependence of the diffusion coefficient taken from the permeation experiments in the high concentration region is predicted by a surface diffusion mechanism in which two true adsorption equilibria of the Langmuir type are established throughout the nylon, whereas only a pseudo-equilibrium adsorption of the Nernst type is achieved.     

Wet spinning of aliphatic and aromatic polyamides

Bench-scale equipment for wet spinning was designed and built. An experimental study of the wet spinning of several polyamides has been carried out. The polymers studied include nylon 6, nylon 66, redissolved Nomex, and redissolved Kevlar. The superstructure of the wet-spun fibers were studied by optical and scanning electron microscopy as well as small- and wide-angle x-ray diffraction. Mechanical properties were measured and related to the spinning variables. For nylon 6 and nylon 66, the coagulation bath composition was found to be of major importance in determining fiber superstructure. For the case of the redissolved Kevlar, anisotropic spinning dopes were obtained from redissolved fiber, and the wet-spun filaments produced from such solutions were investigated. These fibers proved to have relatively high modulus and strength as spun. They had even greater strengths after hot drawing.     

Mechanical and some other properties of acrylic-monomer-grafted nylon 6 fiber

Nylon 6 fiber, grafted with various vinyl monomers, viz., methyl methacrylate (MMA), ethyl methacrylate (EMA), and n-butyl methacrylate (n-BMA) were evaluated for their tensile, dye uptake, moisture regain, and solubility characteristics and compared to those of the parent nylon 6 fiber. The tensile properties (tenacity and initial modules) of the grafted samples show a decreasing trend and the percentage breaking elongation an increasing trend with the increase in the graft level in the case of all the three monomers compared to parent nylon 6 fiber. Disperse dye uptake also shows a decrease with the increase in the graft level in all the three monomers grafted only onto nylon 6 fiber. With the introduction of hydrophobic groups in the polymer backbone the moisture regain values decrease. This is true for all the samples and follows the order MMA-g-nylon > EMA-g-nylon > n-BMA-g-nylon. Solubility of the polymer in the solvent orthochlorophenol (OCP) and metacresol (MC) also decreases with the increase in the graft level for all the three monomers used in the following manner: OCP: EMA-g-nylon > n-BMA-g-nylon > MMA-g-nylon; MC: n-BMA-g-nylon > EMA-g-nylon > MMA-g-nylon.     

Properties of bio‐based polymer nylon 11 reinforced with short carbon fiber composites

In this work, micro‐composite materials were produced by incorporating 3‐mm long reclaimed short carbon fibers into bio‐based nylon 11 via melt compounding. A systematic fiber length distribution analysis was performed after the masterbatching, compounding and an injection moulding processes using optical microscopy images. It was found that the large majority of the fibers were within the 200–300 μm in length range after the injection moulding process. The mechanical (flexural and tensile), thermo‐mechanical, and creep properties of the injection moulded materials are reported. We found that an enhancement in flexural and Young's modulus of 25% and 14%, respectively, could be attained with 2 wt% carbon fiber loading whilst no significant drawback on the ductility and toughness of the matrix was observed. The creep resistance and recovery of the nylon 11, tested using dynamic mechanical thermal analysis at room temperature and 65°C, was significantly improved by up to 30% and 14%, respectively, after loading with carbon fiber. This work provides an insight into the property improvement of the bio‐based polymer nylon 11 using a small amount of a reclaimed engineered material. POLYM. COMPOS., 36:668–674, 2015. © 2014 Society of Plastics Engineers