Interaction of dyes used for foods with food packaging polyamides

The effect of pH, temperature, dye concentration, and additives on the adsorption of the dyes FD & C (Food, Drugs & Cosmetics) Blue 1 and Blue 2 upon the polyamides nylon 4–7,9, and 10–12 was studied and a correlation between these parameters and the dye uptake was found. The adsorption kinetics of the dyes on the polyamides were studied and a mechanism based on the interaction of the acid groups of the dyes and the positively charged groups of the polyamides was suggested. © 1993 John Wiley & Sons, Inc.     

Synthesis and properties of new cationic surfactants

New pyrimidinium cationic surfactants containing a positively charged nitrogen atom of the pyrimidine ring and a long-chain alkyl group of 6,8,10,12,14 carbon atoms were prepared. The structural assignment of these compounds was made on the basis of the elemental analysis and spectroscopic data, infrared, nuclear magnetic resonance and mass spectroscopy. Surface tension and after-treatment of direct dyed cotton fabrics were determined for these surfactants. Antibacterial activities also were examined.     

Photocatalytic oxidation of Cibacron Yellow LS-R

The photocatalytic degradation of Cibacron Yellow LS-R (CIY), an azo dye, has been investigated in aqueous heterogeneous solutions containing semiconductor oxides as photocatalysts. The disappearance of the organic molecule follows approximately a pseudo-first kinetic order according to the Langmuir–Hinshelwood model. Various commercial photocatalysts are compared with respect to their decolorization efficiency, the COD, as well as the toxicity reduction. The effect of the temperature on the reaction rate is ascertained.     

Digital and conventional printing and dyeing with the natural dye annatto: optimisation and standardisation processes to meet future demands

The plant colorant annatto was investigated to determine its potential use as a natural dye for conventional and novel textile applications. Alum was selected as a mordant. Different techniques of mordanting and a broad set of variations in the dyeing recipes were applied to achieve optimisation and an improvement in colour fastness properties. Quality control of all dyeings was performed using standard fastness tests and colour measurements. Printing of cotton fabrics was also achieved with annatto using the flatbed screen‐printing technique. Measurement of the rheological and physical properties of the annatto printing paste confirmed its stability and suitability for conventional printing. Fastness properties of the conventionally printed annatto fabric were also measured. A novel water‐based digital printing ink using annatto was prepared and applied to cotton fabric using a digital printing application. The physical properties of the annatto ink‐jet ink were also measured. Wash, light and rub fastness properties of the annatto digitally printed fabric were determined and compared with those of conventional printing methods. The results were promising for annatto as a natural colorant, which possibly paves the way for the development of a new range of natural environmentally friendly dyes.     

Synthesis and characterization of hetarylazo disperse colorants: Preparation and properties of conventional and microemulsified inks for polyester ink‐jet printing

The synthesis and characterization of three hetarylazo disperse colorants are described. These compounds were used for the preparation of conventional inks and/or oil‐in‐water microemulsions (microemulsified dyes). The viscosity, conductivity, surface tension, and pH of these inks were studied over a period of time and discussed with respect to their structure. The particle size and particle size distribution of a representative microemulsion were compared to those of a corresponding conventional ink. The measured properties were compared to the properties of commercially available inks. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Pyrimidinium cationic surfactants as emulsifiers for oil-in-water emulsions

Pyrimidinium cationic surfactants with 13–17 carbon atoms in the hydrophobe were used as emulsifiers for oil-inwater (heptane/water) emulsions at concentrations near the critical micelle concentrations. Interfacial tensions of the emulsifier solutions in water against heptane were measured. Drop size distributions of the emulsions were determined at different times using microscopic techniques, and the rate of coalescence was calculated. The structure having 16 carbon atoms in the alkyl chain had coalescence rates lower than the other structures, including two conventional C-16 cationics used as controls.     

Reactive dyeing of cellulosic fibers: Use of cationic surfactants and their interaction with reactive dyes

Cotton fabrics were dyed with three reactive dyes, C.I Reactive Blue 263, C.I Reactive Red 269, and C.I Reactive Yellow 208, after pretreatment of the fabrics with three alkyl trimethyl‐ammonium bromides (tmabs) having 12, 14, and 16 carbon atoms in the alkyl chain. The pretreated samples were dyed with standard dyeing methods using conventional, reduced amounts of electrolyte, and no electrolyte. Pretreatment with the three cationics (tmabs) resulted in an increase in dye exhaustion with all dyes used, whereas total dye fixation was lower for both red and blue dye and equal for the yellow, when compared to the reference untreated samples dyed according to the same standard dyeing method. The interaction between dodecyl trimethyl‐ammonium bromide and the three dyes was studied and the stoichiometry of the various dye/dodecyl trimethyl‐ammonium bromide (12‐tmab) complexes formed has been deduced. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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     

Identification of nylons by thin layer chromatography

The composition of nylons by ω-amino-carboxylic acid monomers, dicarboxylic acids, and diamines is identified by thin layer chromatography, using their acid hydrolysates and determining the corresponding R_f values.     

The colour and fastness of natural saffron

Cotton and wool fabrics have been dyed with the aqueous extract of saffron containing α-crocin as the main colorant species. The dyeings were carried out with and without metal salts as mordants. The wash and light fastness of the dyed fabrics was studied. The colour of the fabrics was investigated in terms of CIE L* C* H* values.