JOURNAL OF COLOR SCIENCE AND TECHNOLOGY
Year:2012 | Volume:6 | Issue:1|Papers Count:11

In this research optimization of water -based overprint clear coat on printed substrate (flexography) was investigated and optimized by the Design Expert 7 software. The nano silica, Tinuvin 400 and water were the components in composition of overprint clear coat, which affect properties of clear coat. So these components were considered as variable factors in a mixture experimental design and their effects on clear coat properties were studied. Measurements of some physical and mechanical properties such as light fastness, gloss, abrasion resistance and adhesion were carried out on samples. These factors and their interactions effects were determined analysing the results and finally, the optimized regeons on the contour diagrams were obtained.

In this research, a nanoceramic hexafluorozirconic acid based conversion coating free of phosphate salts was investigated. The effect of practical parameters such as solution pH, temperature and dipping time on coating morphology and anti-corrosion resistance of coating was evaluated. Anti-corrosion resistance of so-called nanoceramic conversion coating on cold rolled steel (CRS) substrates in different solution pH, temperatures and immersion’s time, utilizing DC Polarization was studied. The conversion coating which was formed at dipping temperature of 20oC, pH=5 and immersion’s time of 60 seconds had the best anti-corrosion resistance. The morphology of the conversion coating surface formed at different pH was investigated using Atomic Force Microscopy (AFM). Images obtained from the microscope indicate that the conversion coating which formed in pH=5 was more consistent and had finer aggregates in comparison with pH=4.25 coating. Field Emission Scanning Electron Microscopy (FE-SEM) of conversion coating formed in 20 and 40oC indicated that surface of conversion coating with higher temperature had micro cracks and was not uniform, also nodules on the scale of tens of nm (40–60 nm) in size, was observed on the surface.

In this study, the photocatalytic ozonation of Reactive Red 2 (RR2) and Reactive Red 120 (RR120) in aqueous solutions under UV irradiation was investigated using ZnO as a photocatalyst. The effect of operating parameters such as catalyst dosage, pH, initial dye concentration and salt on the decolorization was studied. UV/vis spectrophotometric was used to assess dye decolorization. The results showed that the best pH value and ZnO dosage were 3 and 15 mmol/l, respectively. The dye decolorization enhanced with decreasing initial dye concentration. Sodium sulfate had no significant effect on dye decolorization process but sodium bicarbonate and sodium carbonate increased decolorization time. The results shown that the photocatalytic ozonation process was an effective method to degrade reactive dyes.

The hematite as a natural and non-toxic red pigment has been known since prehistoric times but colour shade of hematite becomes unstable with high temperature and needs to be protected with a suitable composite matrix. In this research stability of hematite has been increased by encapsulation of its nano particles in well-known ceramic matrix with high termal-chemical stability. Synthesis of this kind of pigment regard to importance of in situ formation of two phases of composite must be wet chemical routes. At first nano hematite particles were synthesized with same mole ratio into silica, alumina and zircon matrix separately and binary. Then synthesized gels were calcinated and sintered in the furnace at 1250oC. In order to comparision of stability and quality of product, some studies on the nanocapsulate pigments have been done such as X-ray diffraction, colorimeter, scanning and transmission electron microscopy. The synthesized hematites have spherical morphology and particle size about 10-20 nanometer. The best inclusion system was prepared in zircon casings but the best red shade was obtained in alumina system.

In this research a novel organic-inorganic hybrid nanocomposite based on 3-glycidyloxy propyl trimethoxysilane and methyl red dye was synthesized by the sol-gel processing. Structural properties were characterized using FT-IR spectroscopy and TEM. Optical performance was studied by birefringence test using different concentrations of dye between 3 and 20 wt%. Results obtained from this experiment were analyzed in three sections including pump irradiation start-up, equilibrium and pump irradiation cut off (memory effect). Results were fit using a 3 parameter equation. Time dependent parameters were attributed to the memory effect. It was revealed that samples with 8% of dye had the best birefringence effect. However, samples composed of 10 wt% dye showed the best memory effect. Results showed that these nanocomposites can be used in modulators.

At the present study, the fundamental color stimulus space (N*) obtained from the Cohen and Kappauf decomposition technique as an alternative to the measured spectral reflectance (N) was investigated. Based on the single-constant Kubelka-Munk theory, the (K/S)* space from the non-linear transformation of N* values was obtained and its consistency with (K/S) space taken from the measured reflectance was spectrally analyzed. The scalability for both spectral spaces was quantitatively evaluated in different concentrations through visible spectrum. The suitable wavelengths that (K/S)* still exhibit linear behavior with concentration variation were introduced. The obtained results showed that the non-linear transformation of fundamental color stimulus space, i.e. (K/S)* is more scalable. At the proposed wavelengths, the applicability limit of (K/S)* similar to the (K/S) is improved till the higher dye concentration and the obtained linearity for (K/S)* could be an proposed approach for the study of dyeing systems such as estimating the concentration from tristimulus values as colorimetry data.

In this research a novel monoazo disperse dye was prepared from r-aminobenzoic acid as the diazo component and 3-N,N-diethylaminoacetanilide constituted the coupling component. The synthesized dye was purified by recrystallisation method and then was characterized by analytical instruments such as DSC, FTIR, Mass spectra, 1HNMR, 13CNMR and UV-Visible techniques. The synthesized dye was applied on polyester fabric according to HT method. Dyeing and fastnesses properties of synthesized dye on polyester fibres were investigated. The results showed that the synthesized dye had good build-up, excellent wash fastness and good light fastness on polyester fibres. Also, the elimination of the reduction clearing and its replacement with alkali clearing process of dyed fabrics was evaluated. The results represented that the synthesized dye is hydrolysable and removable from the surface of dyed polyester fabrics under alkaline condition. To this reason the reduction clearing process and consuming of sodium hydrosulfite were eliminated in the dyeing of polyester using the synthesized dye.

Pre-treatment of cotton fabric by poly (propylene imine) dendrimer enhanced its color strength using C.I DIRECT RED 81 and C.I. DIRECT BLUE 78. Application of this dendrimer and the direct dyes simultaneously on cotton fabric by exhaust as well as continuos dyeing method has been studied with slightly improved dyeing results. Pre-treatment of the cotton fabric with dendrimer in emulsion form using pad-dry method, followed by continuous dyeing, increased in color strength and level dyeing as well as light and wash fastness was achieved. The use of the dendrimer in emulsion form prevents the aggregation of dendrimer. As a result, level dyeing with C.I. DIRECT RED 81 and C.I. DIRECT BLUE 78 dyes as well as satisfactory color strength has been noticed.

In this study, the electrochemical behavior of phosphoric acid and tannin mixture as rust converter solutions is investigated. Experimental design was carried out using taguchi method as a useful tool to interpret the results. A variable was studied comprising weight percentage of phosphoric acid and tannin, pH of pretreatment solutions and immersion time of rusted specimens in pretreatment solutions. Polarization test was utilized to measure the corrosion rate of conversion layer and optimization of pretreatment solutions in term of inhibition efficiency. Also, characterizing experiments including SEM-EDX, XRD and FT-IR were carried out on samples treated in optimum condition. Polarization test results showed that a solution containing no tannin and phosphoric acid (20 wt%) in pH=2 and immersion time equal to 5 hours exhibited the optimum condition in term of inhibition efficiency. XRD and FT-IR tests showed that a phase transformation of rust layer occurred after treatment and the conversion layer treated in optimum condition revealed suitable corrosion protection of metallic substrate.

In this work, the catalytic degradation of C.I. Reactive Red 120 (RR120) using magnetic nanoparticles of cobalt-iron oxide in the presence of hydrogen peroxide was studied. The magnetic nanoparticles of cobalt-iron oxide have been prepared by modified sol-gel method and have been characterized by XRD, TEM and VSM methods. The prepared nanoparticles were nanocrystalline pure single-phase and with particle sizes of 16-21 nm. Values of saturation magnetization, remanent magnetization and coersivity were found to be 68 emu/g, 31 emu/g and 1824 Oe, respectively.The magnetic nanoparticles of cobalt-iron oxide showed its catalytic effect for dye degradation over a wide range of pH=2-8 with a maximum effect at pH=2-3. The decolorization rate increased by increasing the amount of catalyst, the concentration of hydrogen peroxide and temperature. The optimal condition for complete decolorization of RR120 (50 ppm, 50 ml) was found to be 0.1 g/l of catalyst, 10 mM hydrogen peroxide at pH=3 and 75oC. The recovered nanoparticles of cobalt-iron oxide showed almost the same catalytic activity as the first time after 6 cycles of recovery and reuse.