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Journal of Coatings Technology and Research

Current research reports and chronological list of recent articles..




The international scientific Journal of Coatings Technology and Research - JCTR - is a forum for the exchange of original research, experience, knowledge and ideas among those with a professional interest in the science, technology and manufacture of functional, protective and decorative coatings including, but not limited to, paints, inks and related coatings and their raw materials.

The publisher is Springer. The copyright and publishing rights of specialized products listed below are in this publishing house. This is also responsible for the content shown.

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Additional research articles see Current Chemistry Research Articles.



Journal of Coatings Technology and Research - Abstracts



The reinforcing effect of crosslinkable waterborne polyurethane/polysiloxane composite emulsion by aqueous sol–gel method

Abstract

A highly branched polysiloxane (S2) was prepared by an aqueous sol–gel process and used as an underlying crosslinker to modify silanized waterborne polyurethane (WPUS), and a novel crosslinked waterborne polyurethane (WPU)/polysiloxane composite with low VOC features was obtained. The good dispersibility of polysiloxane (S2) was proved by both TEM and DLS analyses, implying that the polysiloxane had an excellent intermiscibility with the WPU. The larger silsesquioxane network in the composite was proved by XPS, which was generated from the condensation of the Si–OH groups of polysiloxane and WPUS. On the basis of tensile results, the content of polysiloxane had a significant impact on the mechanical properties. The reinforcing and toughening synergy effect was found in the composite with a low concentration of S2. According to micrographs of the fracture surface, the dominating toughening mechanism was dependent on microcracks, while the high concentration of polysiloxane turned into silica particles in the WPU matrix, resulting in force concentration and degradation of the mechanical properties. However, the Young’s modulus increased with the increasing content of S2. Additionally, the incorporation of the crosslinked silsesquioxane structure also improved the hydrophobic properties and thermal stability of the composite.


Datum: 17.09.2019


Development of functionalized SiO 2 –TiO 2  reinforced cardanol and caprolactam modified diamine based polybenzoxazine nanocomposites for high performance applications

Abstract

In the present work, three types of polybenzoxazines were synthesized using caprolactam-based diamine (CPA-NH2) and formaldehyde with different phenols, namely 4-fluorophenol, cardanol, and phenol, under appropriate experimental conditions. The molecular structure of the benzoxazine monomers was confirmed by FTIR, 1H, and 13C NMR spectroscopic techniques. Polybenzoxazines were obtained through ring-opening polymerization of benzoxazine monomers, and their formation was confirmed by FTIR spectroscopy. The elemental composition and morphological behavior of polybenzoxazines were characterized by SEM-EDAX and AFM techniques. The naturally occurring cardanol- and caprolactam-based diamine (CPA-NH2)-based benzoxazine was selected for detailed studies. The synthesized SiO2–TiO2 nanohybrid reinforcement was functionalized with 3-aminopropyltrimethoxysilane (3-APS) and reinforced with cardanol-based benzoxazine (CPBz) monomer. The resulted nanocomposites were studied for their corrosion protection behavior against mild steel surface along with thermomechanical (TGA and DMA) and morphological (SEM, XRD, and TEM) properties. The results obtained from electrochemical impedance analysis indicate that the 5 wt% of F–SiO2–TiO2 of reinforced CPBz exhibits an effective corrosion-resistant behavior toward surface of steel specimen than that of other samples.


Datum: 12.09.2019


Near-IR sintering of conductive silver nanoparticle ink with in situ resistance measurement

Abstract

Metal nanoparticle inks are excellent options for printing low-resistance metal conductors and electrical interconnects. However, after deposition, these inks require high-temperature annealing to sinter and increase conductivity. Infrared (IR) heaters are an efficient, roll-to-roll compatible method to apply thermal energy. Here, we characterize the effect of near-infrared (N-IR) heating on the structure and properties of printed silver nanoparticle ink (UTD Ag40x, UT Dots Inc.). A method was developed to measure the resistance and temperature of printed conductive inks as a function of exposure to the IR heater. The N-IR heater was found to sinter the Ag40x silver samples (lower the resistance of 7 mm printed lines to 1000 Ω) in 11.6 ± 1.5 min at maximum intensity with a large drop from the highest measured resistance (60 MΩ) to 1000 Ω in 1.2 ± 0.2 min. Decreasing the heater power increased the time to reach 1000 Ω (to 28.3 ± 2.0 min at 80%), but reducing from 60 MΩ to 1000 Ω still only took 1.9 ± 0.3 min. This suggests sintering progresses rapidly once initiated. SEM images of the ink before and after IR heating show microstructural changes associated with sintering and indicate the role of agglomerates and organic binders in impeding sintering.


Datum: 12.09.2019


Isosorbide-derived boron- and phosphorus-containing precursors for flame-retardant epoxy coating

Abstract

The present study describes an attempt to induce the inherent flame retardancy to the epoxy resin by incorporation of phosphorous and boron atoms in the polymer backbone through the curing agents. Phosphorous (PPc)- and boron (BPc)-containing precursors were synthesized and incorporated into the commercial epoxy and hardener system with different molar ratios. The structures of the synthesized compounds were confirmed using hydroxyl value, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy. The thermal, physical, and mechanical properties of the cured films were performed using different testing methods. Thermogravimetric analysis and differential scanning calorimetry results showed the overall increased thermal stability and char yield along with the glass transition temperatures (Tg) due to the incorporation of newly synthesized phosphorus- and boron-containing compounds in the coating films. The mechanical properties and solvent resistance of the cured films were excellent. The flame-retardant properties of the cured films were increased with the incorporation of PPc and BPc. The highest limiting oxygen index was obtained for the formulation with equal amounts of PPc and BPc as 29 while UL-94 showed the self-extinguishing behavior within 10 s after ignition.


Datum: 11.09.2019


Polymethylsilsesquioxane powder prepared by morphology-controlled growth and its composite with waterborne latex for superhydrophobic coating fabrication

Abstract

The incompatibility of superhydrophobic particles with waterborne latexes impedes the direct mixing of them to make mixtures for superhydrophobic coatings fabrication. Polymethylsilsesquioxane (PMSQ) prepared by methyltrialkoxysilane precursors can change from hydrophilic to hydrophobic with the increased degree of condensation. This property makes PMSQ suitable for compounding with waterborne latexes for highly hydrophobic coatings fabrication. The present work presents a method for the morphology control of PMSQ to make highly porous PMSQ particles with micro-/nano-roughness on the surface. A gel of PMSQ was first prepared in aqueous medium and broken into small pieces by a high speed homogenizer; additional acid-catalyzed hydrolyzate of methyltrimethoxysilane was added to this dispersion of broken particles. The following base-catalyzed regrowth of PMSQ on the preformed gel skeleton gave highly porous PMSQ powder suitable for compounding with waterborne latexes. The composite of PMSQ wet powder and a styrene-acrylate waterborne latex gave a superhydrophobic coating after drying in ambient condition, of which the water contact angle reaches 153.1° and sliding angle is low to 28.7°.


Datum: 01.09.2019


Colloidal, morphological, thermal, rheological, and film properties of waterborne hyperbranched alkyd–acrylic resins

Abstract

Waterborne hyperbranched alkyd–acrylic resins (HAAR) are interesting materials that provide excellent properties yet require only low levels of solvent in formulations using them. However, they have been scarcely studied. Therefore, the goal of this work was to prepare and evaluate various properties of HAAR. These materials were obtained by miniemulsion polymerization from a hyperbranched alkyd resin (HAR), methyl methacrylate (MMA), butyl acrylate (BA), and acrylic acid (AA). The proportions of HAR:acrylic monomers were as follow: 50:50 (HAAR1), 40:60 (HAAR2), 30:70 (HAAR3), and 20:80 (HAAR4). The particle size increased with the content of HAR, but the colloidal stability, critical deformation, zeta potential, thermal stability, and hardness followed an opposite behavior. The order of colloidal stability of the HAAR miniemulsions was HAAR4 > HAAR3 > HAAR2 > HAAR1. The particle morphology of the HAAR was mainly core–shell, but acrylic and alkyd particles were also observed. In addition, all HAAR initially exhibited a reduction in complex viscosity (η*) with the increase in angular frequency. The thermal stability of the HAR was lower than that of the HAAR. The HAAR showed better resistance against a 0.10 M sodium hydroxide (NaOH) solution than HAR.


Datum: 01.09.2019


Phosphorus-containing reactive agent for UV-curable flame-retardant wood coating

Abstract

An attempt to develop a phosphorus-based flame-retardant UV-curable agent (UV-RA) for coating application led to the synthesis of a reactive compound which can be used as crosslinker along with UV-curable epoxy acrylate oligomer to form a coating. UV-RA was characterized via FTIR, NMR, hydroxyl, and iodine values. Study based on the effects of varying amount of UV-RA incorporated in the formulation was investigated by checking thermal, mechanical, and flame-retardant properties. An enhancement in all the properties was observed with an increase in concentration of UV-RA and each coating containing UV-RA successfully portrayed flame-retardant properties. The highest loss on ignition (LOI) value obtained was 27 while the initial and final degradation temperatures increased along with the char yield. The mechanical properties did not vary much except for the low values for 20UV-RA.


Datum: 01.09.2019


Environmentally friendly Zn–Al layered double hydroxide (LDH)-based sol–gel corrosion protection coatings on AA 2024-T3

Abstract

Zn–Al layered double hydroxide (LDH) intercalated with various corrosion inhibitors namely vanadate (E1), 2-mercapto benzothiazole (E3), molybdate (E7), phytic acid (E8) and 8-hydroxyquinoline (E9) was dispersed in a hybrid sol–gel silica matrix sol. Bilayer coatings with configurations E3|E1, E7|E1, E8|E1 and E9|E1 were generated on aluminum alloy AA 2024-T3 substrates using the inhibitor intercalated LDH modified sols by dip coating technique followed by UV curing and thermal curing at 80°C for 1 h in air. Corrosion resistance of coatings deposited from matrix sol with and without inhibitor intercalated LDH was studied by electrochemical impedance spectroscopy, potentiodynamic polarization after exposure to 3.5% NaCl and salt spray tests, results of which were compared with those of uncoated and chromated substrates. A non-chromated primer was applied on the sol–gel coated substrates. Adhesion of the coatings to the substrate and to the primer was evaluated by peel-off tape test and found to be rank 5. The sol–gel coated substrates did not exhibit corrosion during salt spray tests. Electrochemical tests showed that all the sol–gel coated substrates exhibited superior corrosion resistance when compared to bare and chromated substrates. More specifically, coatings generated using the corrosion inhibitors phytic acid and 8-hydroxy quinoline intercalated Zn–Al LDH were seen to render maximum corrosion protection, exhibiting two orders of magnitude lower corrosion currents than bare substrates and one order lower corrosion current than chromated substrate, after 120-h exposure to 3.5% NaCl solution.


Datum: 01.09.2019


Effect of operating parameters on the structural growth of ZnAl layered double hydroxide on AA6082 and corresponding corrosion resistance properties

Abstract

In this study, a series of ZnAl layered double hydroxide (ZnAl-LDH) thin films were synthesized on an AA6082 alloy by a single-step hydrothermal process at different synthesis parameters, including reaction temperature, reaction time, pH, and the relation between the LDH structural variations, and the corresponding corrosion resistance properties are briefly reported. The as-prepared synthetic coatings were characterized by scanning electron microscopy and X-ray diffraction. The corresponding corrosion properties were evaluated through potentiodynamic polarization curves and through electrochemical impedance spectra. The findings demonstrated that synthesis parameter variations impart an influential effect on the geometry of LDH, film thickness, and structural morphologies which have a significant  impact on LDH corrosion resistance properties. The ZnAl-LDH corrosion resistance was found to increase with respect to extended high temperature and aging time, while the synthetic pH conditions also promoted LDH growth and film thickness, relative to lower-pH reaction conditions. The optimization results are attributed to high ZnAl-LDH corrosion resistance and act as a strong barrier film and ion-exchange surface area. The ZnAl-LDH films at 80°C-18r-6.5pH have shown much lower corrosion current density compared to bare AA6082, and a decrease of up to five orders of magnitude is observed.


Datum: 01.09.2019


Formulation development and characterization of highly water-soluble drug-loaded extended-release pellets prepared by extrusion–spheronization technique

Abstract

The objectives of current study were (a) to prepare extended-release plain (without polymers) and matrix pellets of itopride hydrochloride (ITP) by extrusion and spheronization technique, (b) to control the initial fast release of drug from the matrix pellets by coating using ethylcellulose, Eudragit® RL/RS100 (2:1), and Kollicoat® SR 30D, and (c) to investigate the influence of different types and concentration of coating polymers on release of highly water-soluble drug. The plain pellet contained microcrystalline cellulose and lactose without polymer, whereas matrix pellet formulations were composed of hydroxypropyl methylcellulose (HPMC K4M, K15M, and K100M) and ethylcellulose (EC 7 cps). Matrix pellet formulations failed to control the drug release, up to targeted period of 12 h. Five pellet formulations—one without polymer (F1) and one from each polymer category (F4, F7, F10, and F13)—were screened out for coating using different types and levels of polymers. The DDSolver (an add-in software for MS Excel) was used to analyze the dissolution profile data for drug release kinetics. However, drug release from pellet formulation (F7) containing HPMC as a matrix former and coated with EC followed zero-order kinetics (R2 = 0.897–0.998). The release mechanism of EC-coated formulations F7, F10, and F13 was non-Fickian diffusion (anomalous transport), whereas F1 and F4 were Fickian diffusion mechanism. The stability studies of all 5% EC-coated ITP pellet formulations were conducted at room and accelerated temperature as per ICH guidelines, and results were found satisfactory. It is concluded that ethylcellulose other than Eudragit® RL/RS100 (2:1) and Kollicoat® SR 30D was found to be an excellent release controlling agent for ITP which showed good controlled-release characteristics.


Datum: 01.09.2019


Steering and in situ monitoring of drying phenomena during film fabrication

Abstract

During film fabrication, the phenomena of crack formation and delamination are often observed, dramatically hindering the discovery and characterization of new materials for energy applications. In this work, we report on a novel approach to fully steer the drying parameters or “knobs” that are commonly used during electrode manufacture. It allows us to precisely in situ control and monitor the solvent-specific evaporation rates that affect the development of suspension composition during drying. We managed to control the capillary stress inside the layer by precisely controlling the selectivity of solvent evaporation. Large cracks result when the surface tension increases over time and layer delamination occurs. When using an n-propanol/water system, critical crack formation is achieved when water is enriched by decreasing the gas exchange during drying or preloading the gas phase with water vapor. High gas exchange rates inhibit the water’s enrichment, and therefore, only small surface cracks develop. The experiments also surprisingly indicate that the drying temperature has no significant effect on crack formation. These results are of fundamental meaning for the future development of electrodes as the drying step has a high impact on the products specification and now can be ultimately controlled. The future development of electrodes will surely benefit from this achievement in the controlled fabrication of films for a variety of applications.


Datum: 01.09.2019


Electrophoretically deposited graphene oxide–polymer bilayer coating on Cu-Ni alloy with enhanced corrosion resistance in simulated chloride environment

Abstract

An environmentally benign and facile bilayer coating comprised of graphene oxide (GO) and acrylic polymer is fabricated over cupronickel sample using electrophoretic deposition followed by dip coating. The infrared, Raman, and field emission scanning electron microscopy (FESEM) studies of the bilayer coating confirm the noncovalent functionalization of GO through H-bonding with acrylic polymer, reduction in local defects in GO structure, and distorted spherical void peripheries of polymer coating, respectively. The FESEM cross-sectional analysis showed that the coating thickness is 5–6 µm. The bilayer-coated sample showed a three- to fourfold increase in the corrosion resistance, as compared to GO-alone-coated sample in 3.5% (w/v) NaCl electrolyte, which is attributed to the reduction in the local defects in GO coating and the galvanic coupling between the GO and sample surface. The GO sheets make the diffusion pathway of corrosive media more tortuous for corrosive ions to reach the metal surface. The lower anodic current density observed with the new bilayer coating after 30 days of exposure confirms the active corrosion protection. The coating was intact and stable after 30 days of exposure in chloride medium with a water uptake of about 32.7%.

Graphical abstract


Datum: 01.09.2019


UV-curable waterborne polyurethane dispersions modified with a trimethoxysilane end-capping agent and edge-hydroxylated boron nitride

Abstract

In this study, waterborne polyurethane (WPU) dispersions were prepared using a trimethoxysilane end-capping agent (DAA-GPTMS) derived from diallylamine (DAA), (3-glycidoxypropyl)methyldiethoxysilane (GPTMS) and modified with edge-hydroxylated boron nitride (hBN-OH) nanosheets. The WPU films containing DAA-GPTMS possessed remarkable hydrophobicity and favorable water repellency, attaining a contact angle of 101.2° and a 52% decrease in water absorption relative to those of the pure WPU. When the contents of DAA-GPTMS and hBN-OH were 7.5 wt% and 0.2 wt%, respectively, the synergetic effect between the DAA-GPTMS and the hBN-OH nanosheets greatly enhanced the physical and mechanical properties of the nanocomposite films, i.e., the stress doubled and the Young’s modulus increased by fivefold compared to those of pure WPU. Embedding 0.2 wt% of the hBN-OH nanosheets in the WPU coatings resulted in a lower corrosion current density (1.0 × 10−10 A cm−2) and more positive corrosion potential (− 0.63 V). The results demonstrate that WPU/hBN-OH nanocomposite coatings possess great potential for corrosion protection.


Datum: 01.09.2019


UV-curable waterborne epoxy acrylate coating modified by monomethacryloyloxy-terminated fluorinated oligomer

Abstract

Monomethacryloyloxy-terminated fluorinated oligomers (PPFOMA-GMA and PHFBMA-GMA) and methyl allyl alcohol polyoxyethylene ether-modified epoxy resin (HPEGEA) were successfully synthesized and used as reactive additives and emulsifier for epoxy acrylate, respectively. FTIR, 1H NMR, and GPC were used to characterize the structures of PPFOMA-GMA, PHFBMA-GMA, and HPEGEA. The influence of the concentrations of PPFOMA-GMA and PHFBMA-GMA on the properties of waterborne epoxy acrylate (WEA) resin coatings was investigated. The surface energy of waterborne epoxy acrylate coating was decreased from 38.20 mN/m to 15.31 mN/m by adding just 0.21 wt% PPFOMA-GMA, indicating its high effectiveness in improving the hydrophobic properties of the surface. The surface compositions of the WEA resin coatings (with 0.85 wt% PPFOMA-GMA or 0.85 wt% PHFBMA-GMA) were characterized by XPS. The XPS results confirmed the quantitative enrichment of fluorine atoms on the surface. What is more, the physical properties of waterborne epoxy acrylate coatings prepared with different concentrations of fluorinated reactive additive, such as optical transmittance, adhesion (on glass, PET, and tinplate), pencil hardness, water absorption, and thermal properties, were also analyzed in detail. Hence, the waterborne epoxy acrylate coatings prepared with low concentrations of reactive additives were economical and have potential for large-scale industrial applications.


Datum: 01.09.2019


The influence of hydrophobic protection on building exterior claddings

Abstract

This study presents the results of an experimental campaign with the aim of investigating the hydrophobic protection of three substrates (stone, render, and external thermal insulation composite system—ETICS) with the application of three hydrophobic products: silicon and titanium dioxides-based nanostructured dispersion (HNST); a silane/oligomeric siloxane (HSila/Silox); and a siloxane (HSilox). To determine the effectiveness of the hydrophobic treatments, specimens of the untreated and treated wall coatings were characterized with different laboratory tests. The results showed that all products introduced significant improvements in the hydric properties of the substrates, leading to lower capillary water absorption (98%), water permeability with Karsten pipes (99%), drying index (39%), and higher water repellency assessed through the contact angle (283%). The application of hydrophobic materials also had a negative effect, leading to up to a 227% increase in resistance to water vapor diffusion. Among the assessed wall coatings, the rendering mortar appears to have the best initial performance after the application of all the types of hydrophobic materials tested. In general, the hydrophobic product HSilox was proved to be the most suitable for rendering mortars, while HNST was more appropriate for stone substrates.


Datum: 01.09.2019


A promising ternary nanohybrid of Copper@Zinc oxide intercalated with polyaniline for simultaneous antistatic and antibacterial applications

Abstract

In this study, a facile and cost-effective approach has been developed for fabricating antibacterial and antistatic waterborne polyurethane (WPU)-based coatings by using Polyaniline-Copper@Zinc oxide (P-Cu@ZnO) ternary nanohybrid as a multifunctional additive. The solid-state reaction of copper acetate and zinc acetate salts led to the synthesis of copper clusters on the ZnO nanoparticles (Cu@ZnO). The obtained Cu@ZnO nanoparticles were intercalated with polyaniline (PANI) chains to prepare the P-Cu@ZnO nanohybrid. FTIR, XRD, UV–Vis, and FESEM analyses were used to characterize the structural, crystallographic, and morphological properties of the synthesized nanohybrid. Adding P-Cu@ZnO nanohybrid to the WPU matrix not only improved adhesion strength of the coatings but also enhanced their scratch resistance compared to the pristine WPU coating. Moreover, incorporation of the obtained nanohybrid into the WPU coatings caused electrical surface resistance of the obtained coatings to reach 1.2 × 10+8 Ω/sq, so, these coatings gained the optimum electrical surface resistance to be counted as an antistatic coating. Also, the results of the colony counting test showed that the modified coatings could reduce the Staphylococcus aureus and Escherichia coli bacteria growth by about 86% and 74%, respectively.


Datum: 01.09.2019


Layer-by-layer films based on polyaniline, titanate nanotubes, and cetyl trimethyl ammonium bromide for antifungal coatings

Abstract

Layer-by-layer (LbL) films have been developed for multiple applications, including functional coatings with antimicrobial activity. In this work, we describe the development of LbL films based on polyaniline (PANI), titanate nanotubes (TiNTs-Na2Ti3O7), and cetyl trimethyl ammonium bromide (CTAB) for applications in antifungal coatings. The LbL films were characterized by spectroscopy in the UV–visible region, cyclic voltammetry, scanning electron microscopy, and atomic force microscopy. Among various films architectures tested, the PANI(TiNTs)/CTAB film was more promising for the suggested applications. This film showed excellent activity against Cryptococcus neoformans fungi, showing inhibition zones. The material developed in this work is a candidate for coating of air conditioning pipes, for instance, since besides the antifungal activity, it also adds the anticorrosive and air-purifying properties present in PANI and TiNTs.

Graphical abstract


Datum: 01.09.2019


Effect of particle shape on the wear and friction behavior of particle-reinforced epoxy coatings

Abstract

Epoxy coatings are increasingly becoming popular choices as barriers against acids and alkali for protection of concrete and metal products. In applications, metal containers are often coated with epoxy-based coatings to prevent rusting and corrosion. In this study, an experimental examination was carried out to investigate the effect of particle shape and size on the friction and wear behavior of epoxy coatings. Friction and wear experiments were conducted using a pin-on-disk tribometer. Epoxy resin was filled with four different shapes of glass particles (spherical, flake, rod, and irregular shape) and varying particle sizes. Fillers were settled down and filler surface area fraction through thickness was characterized using microcomputed tomography (micro-CT). The wear mechanisms such as matrix wear, matrix cracking, particle fracture, particle debonding, and pullout and debris formation were studied using scanning electron microscopy. According to observations, it was found that particle shape has an effect on the wear characteristic. Particle fracture and particle pullout mainly dominated the wear in the samples of flake- and rod-shaped fillers, perpendicular matrix cracks occurred in the samples of spherical fillers, large debonding at the particle–matrix interface without particle pullout occurred in the samples of large irregular-shaped fillers (75–150 µm), and matrix cracks dominated the wear as the size of irregular-shaped fillers decreased to 50–75 µm. Further, it was found that friction coefficient depends on the shape of the particle. The samples with spherical- and irregular-shaped fillers had higher friction coefficient as compared to the samples with flake and rod fillers.


Datum: 01.09.2019


Strong and sustainable chemical bonding of TiO 2 on nylon surface using 3-mercaptopropyltrimethoxysilane (3-MPTMS): analysis of antimicrobial and decomposition characteristics of contaminants

Abstract

In this study, the antimicrobial and photodegradation properties of nylon fabric were improved by chemical treatment using 3-mercaptopropyltrimethoxysilane (3-MPTMS), which binds to photocatalyst TiO2, on a nylon fabric surface. The nylon fibers were impregnated with a solution containing isopropanol, titanium dioxide (TiO2), and 3-MPTMS at optimum ratios, and then stirred for 90 min. To remove the nonreactive impurities, the sample was washed twice with isopropanol and distilled water, and then dried. The TiO2 concentration, agitation temperature, and time were varied to determine suitable coating conditions for attachment to the nylon surface; the resulting properties were confirmed by scanning electron microscopy/energy dispersive spectroscopy. To evaluate the antimicrobial and photodegradation properties of TiO2, antimicrobial tests were conducted using the microbial reduction method and contact angle tests. The fiber contamination rate was measured by computer color matching after the sample was contaminated with methylene blue. Moreover, the antimicrobial activity of Staphylococcus aureus and Escherichia coli strains on the treated nylon was investigated.


Datum: 01.09.2019


Effect of practical parameters on the structure and corrosion behavior of vanadium/zirconium conversion coating on AA 2024 aluminum alloy

Abstract

In this research corrosion behavior of the hexafluorozirconic acid-based conversion coating (ZrCC) applied on the surface of AA2024 aluminum alloy, in the absence and presence of sodium metavanadate (ZrVCC), has been investigated. At the first step, practical parameters of ZrCC conversion coating were optimized using data of polarization resistance (Rp) and corrosion current density (icorr) obtained from electrochemical impedance spectroscopy and polarization techniques, respectively. In the next step the effect of sodium metavanadate presence by assessment on the effect of parameters including concentration of sodium metavanadate, immersion time, and solution pH on surface and electrochemical properties was investigated. The optimized practical conditions for ZrCC were immersion time of 60 s in 0.01 M of H2ZrF6 solution at room temperature and solution pH = 2. For the ZrVCC sample, the best results appeared for the immersion time of 60 s in the bath containing 1 g/lit sodium metavanadate at room temperature and pH = 2. Corrosion current density value of the ZrVCC sample was 0.07 µA/cm2 which seems to be 10 times smaller than its amount for the uncoated sample. Film formation of conversion coatings was investigated by field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM). FE-SEM and EDS test results revealed that zirconium compounds mostly precipitated on the surface of intermetallic particles.


Datum: 01.09.2019


 


Category: Current Chemistry Research

Last update: 28.03.2018.






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