Dual permeation of acid dyes through nylon 6 membrane

Permeation of acid dyes in nylon 6 membrane was measured and analyzed by the dual sorption and diffusion mechanism, comprising partition and Langmuir-type modes. The results were compared with our previous work on diffusion in the same system by the film roll method. Diffusion coefficients of both dye species were found to be similar in magnitude.     

Electrochemical behaviour of polyaniline in aromatic sulphonic acids

This report describes the synthesis and redox behaviour of polyaniline in aqueous solutions of benzene sulphonic acid and 4-toluene sulphonic acid. The characterization of the polymer was carried out by electronic spectra, FTIR studies and ¹HNMR in DMSO-d₆.     

Effects of a bolaform electrolyte on the sorption of acid dyes by a nylon 6 film

The sorption behavior of acid dyes by a nylon 6 film was investigated in the presence and absence of a bolaform electrolyte. The time dependence of the sorption changed with the pH values of the dye bath. At pH 3, equilibrium sorption was not established even after the immersion of the film in the aqueous dye solutions for 7 days, while at pH 4 and in pure water, equilibrium sorption was established after the immersion for 1 day. The sorption isotherms were determined and analyzed by means of the bimodal sorption equation. The sorption parameters thus determined were greatly affected by the dye structure and the pH values. The addition of the bolaform electrolyte reduced the amounts of dye sorbed by the nylon 6 film. This is believed to be due to the formation of the complexes between the dyes and the bolaform electrolyte in the dye bath. Thus, the bolaform electrolyte retards the sorption through the formation of the complexes. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2247–2254, 1998     

Photodegradation of acid dyes in nylon films

The photodegradation of three representative acid dyes commonly used to colour nylon was studied in nylon films. It was observed that irreversible photodegradation of the dyes occurs only at wavlengths shorter than 350nm and that the quantum yield increases as the photolysis wavelength decreases. It was also found that u.v. photolysis of the dyes is partially reversible and that photodegradation is inhibited by oxygen. Evidence is presented that photodegradation occurs by a reduction process, involving hydrogen transfer from the nylon polymer to the excited dye.     

Hydrolysis of aromatic sulphonic acids in industrial effluents. I. Hydrolysis of 7-hydroxy-2-naphthalenesulphonic acid

The protodesulphonation of 7-hydroxy-2-naphthalenesulphonic acid (F-acid) was investigated in dilute aqueous sulphuric acid at temperatures of 522–553 K. The hydrolysis of the sulpho group is irreversible and F-acid can be completely converted into 2-naphthol in a short time. The hydrolysis rate depends strongly on the temperature and on the sulphuric acid concentration; a rate equation was derived from the experimental data.     

Stoichiometry of sulphuric acid sorption by nylon 6

Sorption of sulphuric acid by Nylon 6 has been investigated. The results have been interpreted by considering the two-step dissociation of sulphuric acid in aqueous solution. Sorption occurs predominantly in the 2H⁺ + SO^2?₄ mode, but the contribution of the H⁺ + HSO^?₄ mode becomes considerable at higher concentrations. Standard affinities for both modes have been estimated.     

Influence of acid dyes on the thermal behavior of nylon 66

To reveal the effect of acid dyes on the melt processing of recycled nylon 66, 17 acid dyes with different chemical structures were used to dye a nylon 66 yarn. The thermal stability of dyestuffs, the thermal degradation of the dyed nylon 66 during compression molding, and the melting and crystallization of the dyed nylon were investigated. During melt processing, most dyed nylon 66 changed color strength and color pattern. This is attributed to the migration and chemical reactions of dyestuffs. Acid dyes containing metal ions, such as C.I. Acid Black 60, C.I. Acid Red 186, C.I. Acid Yellow 151, and C.I. Acid Black 107, have severe impact on the thermal stability of nylon 66. The influence of metal complex acid dyes on the thermal stability of nylon 66 can be explained by a mechanism of acid-catalyzed nucleophilic acyl substitution. It was observed that the existence of acid dye in nylon 66 does not influence the melting temperature of nylon. However, some metal complex dyes reduce the crystallization temperature of molten nylon. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 371–382, 1998     

Thermal behavior of nylon 6 copolyamides containing aromatic rings

The thermal behavior of terpolymers of caprolactam (CL) and of hexamethylenediammonium isophthalate (IH) and terephthalate (TH) has been studied in a wide range of compositions by differential thermal analysis. It has been found that either amorphous or crystalline polymers having different crystallization rates can be obtained by changing the composition. The dependence of melting points and glass transition temperatures on the composition has been investigated. The dependence of T_g on the composition for the copolymers CL–IH, IH–TH, and CL–TH has been described by means of the Gordon-Taylor equation. It has been found that this equation fits the experimental data for the IH–TH system only if a parameter which takes into account interactions between the monomeric units is introduced. A ternary iso-T_g map has been obtained through statistical analysis. The influence of the chain stiffness and bulkiness of the monomers on the glass transition temperature is discussed.     

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.     

Quantitative relationships between chemical structure and technical properties of arylazoindole sulphonic acid dyes

A series of arylazoindole sulphonic acid dyes has been synthesised and their spectrophotometric properties have been determined. Their technical properties, such as lightfastness, fastness to washing and substantivity, on nylon and on wool, have been measured.The values obtained of each of these properties have been analysed by a modified Free-Wilson technique. Good correlations with substituent effects have been detained, demonstrating the validity of the additive model in the study of quantitative structure-activity relationships for this set of dyes. The quantification of substituent contributions makes it possible to point out the most active substituents as well as the most critical positions in order to improve the technical properties.     

Hydrolysis of aromatic sulphonic acids in industrial effluents. II. Hydrolysis of amido-J-acid

The kinetics of the acid-catalysed hydrolysis of 6-amino-1,3-naphthalenedisulphonic acid (amido-J-acid) were measured at temperatures of 533–573 K. The only product of the reaction is 2-naphthol, the amino group being hydrolysed much faster than both sulpho groups. The hydrolysis can be described kinetically as a two-step consecutive reaction. Rate constants and activation parameters were determined.     

Quantitative relationships between chemical structure and technical properties of 4-aminoazobenzene sulphonic acid dyes

A series of new 4-aminoazobenzene dyes was synthesised. Absorption maxima and some important technical properties (lightfastness and fastness to washing) on nylon-6.6 and on wool were measured. A number of similar previously described structures were also prepared and characterised. Colour and constitution relationships in this series of dyes were established.A statistical analysis of their fastness properties by a modified Free-Wilson method was carried out. The validity of the additive model was confirmed and quantification of substituent contributions was obtained.     

Diffusion of m-sulfobenzoic acid in nylon 6

Diffusion of m-sulfobenzoic acid in nylon 6 was measured by using the S-35 labelled acid as a tracer. A multimodal mechanism, identical to that in a preceding paper on sorption, was assumed, according to which the protonated acid diffused by dissolution, and the two dissociated acids diffused by competitive interaction with the charged sites in nylon 6. The concentration dependence of the diffusion coefficients was explained by the chemical potential gradient model. The monobasically dissociated species was found to be dominant in the diffusion process. Diffusion coefficients and the activation energies of diffusion did not vary significantly with pH.     

Influence of some aromatic amino acids on the swelling behavior of acrylamide/maleic acid hydrogel

Summary Influence of some aromatic amino acids (histidine, phenylalanine and tryptophan) on the swelling behavior of acrylamide/maleic acid hydrogel (AAm/MA) prepared by γ-radiation was investigated. Swelling tests of AAm/MA hydrogel were made in buffer solutions and amino acid solutions at various pH at 37°C. The pH values are ionization of α-carboxyl groups (pK'₁), α-amino groups (pK'₂) and, isoelectric points (pI) of amino acids. The swelling of AAm/MA hydrogel increased when pH values of solutions were increased. The value of equilibrium swelling of AAm/MA hydrogel was 1035% at pH 10 buffer, while it was 880% at pH 2 buffer. The values of equilibrium swelling of AAm/MA hydrogel in phenylalanine, tryptophan and histidine solutions varied among 1130–1245% at pH 10, while they were among 790–975% at pH 2. The rate constant of swelling, diffusional exponent, network parameter and, diffusion and intrinsic diffusion coefficient were calculated by swelling kinetics. Diffusion of the penetrants into the hydrogel was found to be non-Fickian character. The diffusion coefficients of the hydrogel varied between 3.33×10⁻⁶– 7.71×10⁻⁶ cm ²s⁻¹, while the intrinsic diffusion coefficients waried between 4.03×10⁻⁶– 8.48×10⁻⁶ cm ²s⁻¹. Received: 22 December 1997/Revised version: 3 March 1998/Accepted: 5 March 1998     

Effect of nylon 6 inclusions on the crystalline morphology of polypropylene–nylon 6 blends

Crystallization behavior and crystalline morphology of plain polypropylene (PP) and its blend with 0 to 30 wt % nylon 6 were studied by the hot‐stage polarized light microscopy method. Radial growth rate and the size and number of PP spherulites were measured as a function of both the isothermal crystallization temperature and the nylon 6 content of the blend. The study revealed that a reduction in the isothermal crystallization temperature from 135 to 120°C, for both the plain PP and its blend with nylon 6, leads to the formation of a large number of fast‐growing, small spherulites. Moreover, the size and growth rate of PP spherulites decreased on increasing the nylon 6 content of the blend; whereas the number of PP spherulites decreased sharply on initial addition of 10% nylon 6 and, thereafter, increased slightly by further addition of nylon 6. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1769–1775, 2000     

Isolation of an hydroxy acid concentrate from wool wax acids

Summary The fractionation of the methyl esters of wool wax acids by partitioning between two immiscible solvent layers has been described. Three fractions were obtained: a fraction rich in hydroxyl content, a fraction low in hydroxyl content, and a small amount of hard, transparent, highly colored material. The same procedure when applied to the free wool wax acids did not yield a satisfactory hydroxy acid concentrate. The preparation of wool wax acids with an essentially zero ester number, that is, in a form free of estolides, lactides, and lactones has also been described. Presented at the Spring Meeting, American Oil Chemists' Society, New Orleans, April 20–22, 1959. Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Synthesis and properties of nylon 6 modified with various aromatic polyamides

In this study, flexible nylon 6 was reinforced by the following rigid-chain aromatic polyamides: poly (m-phenylene isophthalamide) (PmIA), poly(4,4′-diphenylsulfone terephthalamide) (PSA), poly( p-diphenyloxide terephthalamide) (POA), and poly(p-diphenylmethane terephthalamide) (PMA). Various high-molecular-weight block copolyamides were synthesized by solution polymerization using p-aminophenylacetic acid (p-APA) as a coupling agent. Their thermal properties have shown that the block copolyamides exhibit higher T_g and T_m and better thermal stability than those of nylon 6, especially PmIA-modified nylon 6. The order of their thermal properties of aromatic modified nylon 6 copolyamides is PmIA > PMA > POA > PSA. Besides, the T_g and T_m of multiblock copolyamides are higher than those of triblock copolyamides. From the wide-angle X-ray diffraction pattern, it is found that the triblock copolyamides have two diffraction peaks (i.e., 2θ = 20.5 and 24°). However, the multiblock has only one at 2θ = 20°, indicating a different crystal structure for multiblock copolyamides. This can be further confirmed from scanning electron microscopy. It shows that the triblock copolyamides are a dispersed phase structure, although the multiblock copolyamides exhibit a homogeneous texture rather than an aggregated one. For the mechanical properties, it is found that the multiblock copolyamides have a more significant reinforcing effect than the triblock copolyamides. Also, the order of their physical properties of aromatic modified nylon 6 copolyamides, such as tensile strength, is PmIA > PMA > POA > PSA; but for the elongation, the order is PSA > POA > PMA > PmIA. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1031–1043, 1998     

Aftertreatment of 1:2 metal complex acid dyes on conventional and microtibre nylon 6. 6 with a commercial syntan/cation system

Dyeings (2% owf) were produced on conventional and microfibre nylon 6. 6 fabrics using unsulphonated, monosulphonated and disulphonated 1:2 metal complex acid dyes. When subjected to the ISO 105:C06/C2 wash test, the wash fastness behaviour of the dyeings was related to the degree of sulphonation of the dyes. Aftertreatment of the dyeings using a commercial syntan improved the wash fastness of the dyeings whereas the sequential application of a cationic compound to the syntanned dyeings caused a further improvement in wash fastness.     

Diffusion of dye mixtures in nylon 6. Binary mixtures of disperse dyes

The diffusion of binary dye mixtures of markedly different chemical constitutions (4-nitro-4′-aminoazobenzene and 1-amino-4-hydroxyanthraquinone) and of similar ones (1-amino-4-hydroxyanthraquinone and 1,4-dihydroxyanthraquinone) into nylon 6 film was examined. Apparent diffusion coefficients of dyes in the mixture within a single dyeing were determined by the film roll method at 60°, 70°, 80°, and 90°C. Diffusion coefficients of individual dyes used in a mixture of chemically dissimilar dyes are found to change little in comparison with single dyeings, while diffusion coefficients of dyes of similar structures are decreased appreciably. It is suggested that the latter effect is due to the interaction between two dyes in the fiber substrate.     

Preparation of hydroxy acids by sulfation of oleic and linoleic acids

Summary Monohydroxystearic acids were prepared by sulfation and subsequent hydrolysis of oleic acid, and the effect of reaction conditions on yield was studied. Monohydroxystearic acids were obtained from commercial oleic acid in 72% yield and from pure oleic acid in 86% yield. Conditions for the best yields apparently gave increased amounts of isomeric hydroxy acids. Hydroxy acids prepared by the sulfation and subsequent hydrolysis of linoleic acid were converted to methyl esters, and purified by fractional distillation and low temperature crystallization. Experimental evidence indicates that sulfuric acid reacts with one double bond of linoleic acid to form isomeric monohydroxyoleic acids and with both double bonds to form dihydroxystearic acids. The by-products formed by the sulfation of linoleic acid include both ester-type polymers and additional polymeric material which cannot be converted to monomers by alkaline saponification. When commercial oleic acid is sulfated and subsequently hydrolyzed, the monohydroxystearic acid thus obtained presumably contains monohydroxyoleic acids and dihydroxystearic acids resulting from the linoleic acid present in the starting material. The formation of an unsaponifiable polymer during the sulfation of linoleic acid accounts in part for the lower yield of hydroxy acids obtained from commercial oleic acid, as compared with that of purified oleic acid. One of the laboratories of the Bureau of Agricultural and Industrial Ohemistry, Agricultural Research Administration, U. S. Department of Agriculture.