Synthesis and performance of alkyd–acrylic hybrid binders

Preparation and properties of alkyd–acrylic hybrids have been studied. Hybrids with different alkyd–acrylic ratios and acrylic parts were prepared via free radical polymerization of acrylic monomers in a presence of an unsaturated alkyd resin using emulsion polymerization technique. The binders were characterized according to their solid content, conversion, viscosity, pH and particle size. Evidence on formation of true copolymer was obtained via NMR spectroscopy and molecular weight and glass transition temperature measurements, as well as via performance studies. The performance evaluation was focused on investigation of drying, penetration and water repellency ability, as well as on film formation and surface topography studies. The binders were compared to references of an alkyd emulsion, acrylic latex and a blend made of them. The results showed that alkyd–acrylic hybrids with synergistic and improved properties can be prepared.     

Synthesis and properties of hybrid alkyd–acrylic dispersions and their use in VOC-free waterborne coatings

Hybrid waterborne alkyd–acrylic dispersions with solid content of 40%, free from any surfactant and exempt of any organic solvent, were successfully synthesized by a melt co-condensation reaction between an acrylic prepolymer bearing carboxylic groups and a long-oil alkyd resin. Spontaneous emulsification of the ensuing hybrid resin was achieved by the addition of an aqueous ammonia solution that neutralized the carboxylic functions. The key role of the carboxylic groups on the stabilization process and on the storage stability of the dispersion was assessed and it was shown that the insertion of anhydride moieties within the acrylic prepolymer ensured the efficient coupling between the acrylic and the alkyd resin and prevented the phase separation. These dispersions are easy to implement and might be used to prepare high quality zero VOC coatings in terms of drying time, stability and gloss. The most stable dispersion was also used in the formulation of air-drying waterborne lacquers and their coating properties were evaluated.     

Structure of tall oil fatty acid-based alkyd resins and alkyd–acrylic copolymers studied by NMR spectroscopy

One- and two-dimensional NMR spectroscopy was used to evaluate the structure of tall oil fatty acid (TOFA)-based alkyd resins and waterborne alkyd–acrylic copolymers. An increase in the functionality of the polyol that is used in the alkyd resin synthesis was found to increase the reactivity of the polyol towards the diacid compared with the TOFA, which causes the formation of more branched and higher molar mass alkyd resin structures. During the copolymerization, polyacrylate chains were grafted to the double bonds and allylic sites of the fatty acid chains in the alkyd resin. Butyl acrylate preferentially grafted to the double bonds, while methyl methacrylate tended to graft to the allylic position. High proportions of the double bonds remaining after copolymerization were crucial to the film formation of copolymers, because the chemical drying of copolymer films occurred by an autoxidation process.     

Sol–gel processing of hybrid nanocomposite protective coatings using experimental design

Environmentally friendly hybrid nanocomposite sol–gel coatings as substitutes for chromate conversion coatings have attracted a great deal of attention recently. The coatings derived from hydrolysis and condensation of polymerizable silane precursors tetraethylorthosilicate (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were deposited onAA5083 substrates by a dip coating technique. Statistical design of experimental (DoE) methodology based on Taguchi orthogonal design has been used to study and optimize compositional and process parameters using multifactor analysis of variance (ANOVA) analysis method and the adhesion strength of coatings to the substrate as per pull off test has been used as a response. Adhesive strength of sol–gel coatings to the substrate was evaluated using pull off and tape tests. Bending, impact resistance and pencil scratch tests were employed to characterize mechanical properties of different coatings. The surface morphology and chemical composition of the hybrid films were studied by atomic force microscopy (AFM) and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR/FTIR), respectively. Optical microscopy (OM) and field emission scanning electron microscopy (FE-SEM) were used to investigate structure of the coatings. The results show an increase of the hydrolysis water content at a constant organic/inorganic molar ratio and other variable parameters increases adhesion of coatings to substrate, and optimum coatings exhibit excellent mechanical properties as well as adhesive to the substrate.     

Synthesis and evaluation of water-reducible acrylic–alkyd resins with high hydrolytic stability

Relatively poor hydrolytic stability is one of the major drawbacks of waterborne alkyd resins. Therefore, the shelf life of the paints containing these kinds of resins is usually short. In this research, the hydrolytic stability of water-reducible alkyd resins has been improved by employing polyacid acrylic copolymers in alkyd resins structure. In addition, the effect of other raw materials (such as neutralizing agent) and synthesis conditions on the resins properties was investigated. The results showed that the optimum synthesized water-reducible acrylic–alkyd resins had a high hydrolytic stability and their acid values increased only 23.5% after 4 months storage at ambient temperature. The synthesized resin was also used in an air-drying water-reducible lacquer formulation and its physical and mechanical properties were evaluated.     

Optimization of platinum dispersion in Pt–PEM electrodes: application to the electrooxidation of ethanol

Nafion® can be used as a solid polymer electrolyte in a PEM fuel cell. Direct platinization of the membrane was realized by chemical reduction of a platinum compound. The platinization procedure was modified to enhance the roughness factor and thus to improve the electrocatalytic activity towards ethanol electrooxidation. The Pt–PEM electrodes were characterized by TEM, atomic absorption analysis, cyclic voltammetry and their polarization curves for ethanol electrooxidation.     

Optimization of platinum dispersion in Pt–PEM electrodes: application to the electrooxidation of ethanol

Nafion® can be used as a solid polymer electrolyte in a PEM fuel cell. Direct platinization of the membrane was realized by chemical reduction of a platinum compound. The platinization procedure was modified to enhance the roughness factor and thus to improve the electrocatalytic activity towards ethanol electrooxidation. The Pt–PEM electrodes were characterized by TEM, atomic absorption analysis, cyclic voltammetry and their polarization curves for ethanol electrooxidation.     

Waterborne acrylic–polyaniline nanocomposite as antistatic coating: preparation and characterization

An antistatic and electrically conductive acrylic–polyaniline nanocomposite coating was successfully synthesized by interfacial polymerization of aniline in the presence of acrylic latex. The acrylic latex was prepared through emulsion polymerization, and aniline was polymerized by in situ interfacial polymerization at the interface of acrylic latex/chloroform phase. Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy and CHNS elemental analysis revealed the existence of 6.24 wt% emeraldine salt of polyaniline (PAni) in the dried film of the nanocomposite. Scanning electron microscopy (SEM) confirmed the presence of colloidal polymer particles in the aqueous phase which was confirmed to have some advantages, including prevention of aggregation of particles, dispersibility improvement and enhancement of the PAni nanofibers aspect ratio in the acrylic polymer matrix. According to SEM results, PAni fibers with the length ranging from 12 to 67 µm and diameters between 0.078 and 1 µm, highly dispersed in the acrylic polymer matrix, were successfully synthesized. Thermal, electrical and mechanical properties of the acrylic copolymer were significantly affected by PAni incorporation. The onset degradation temperature in thermogravimetric analysis revealed that the thermal stability of the nanocomposite was improved compared to that of the pure acrylic copolymer. The nanocomposite film showed electrical conductivity of about 0.025 S/cm at room temperature, along with satisfactory mechanical properties, attractive as an antistatic material in coating applications.     

Optimization of the sputtering process parameters of GZO films using the Grey–Taguchi method

This paper examines the optimization of the process parameters of GZO films deposited on polyethylene terephthalate substrates by R.F. magnetron sputtering using the Taguchi method, aiming to obtain highly transparent and conductive films. The influences of the various sputtering factors (R.F. power, sputtering pressure, deposition time, substrate temperature and post-annealing temperature) on electrical resistivity and structural, morphological and optical transmittance of GZO films are analyzed. The electrical resistivity and the optical transmittance of GZO films were improved by post-annealing the substrate during the deposition process. Experimental results indicate the optimal process parameters in GZO films deposited on polyethylene terephthalate substrates can be determined effectively. The electrical resistivity of GZO films is decreased from 1.194 × 10⁻³ Ω cm to 8.627 × 10⁻⁴ Ω cm and the optical transmittance is increased from 86.148% to 90%, leading to multiple performance characteristics in deposition qualities through the Grey–Taguchi method.     

Investigation of the curing kinetics of alkyd–melamine–epoxy resin system

Properties of coatings based on alkyd resin can be improved via blending with other suitable resins. Recent studies assessed that many properties could be improved by blending with epoxy resins as well as with melamine resins. The aim of this work was to investigate the effect of epoxy resin content on the curing process in alkyd–melamine–epoxy three component blends. The coatings with two mixing ratios of alkyd/melamine (70:30 and 80:20) were formulated. They were made into baking enamels by blending with 3 and 5 wt% of epoxy resin on total resin solid. Curring kinetics was investigated by differential scanning calorimetry (DSC) and application of Ozawa isoconversional method. Fourier transform infrared spectroscopy (FTIR) was used to follow major curing reactions. The absorbance of –OH and –N–CH₂R, showed significant reduction and confirmed that the epoxy resin reacts and inserts in enamel structure. It was found that resin system with alkyd/melamine ratio of 70:30 and 3 wt% of epoxy resin has the lowest apparent activation energy of 141.5 kJ mol⁻¹ and needs the shortest time of 34.2 min to reach final apparent degree of cure. Isothermal DSC experiments have confirmed these findings. The samples with 30 wt% of melamine resin had higher hardness of baked enamels then samples with 20 wt%. They also showed an increase of hardness with the increase of epoxy resin content.     

Optimization of bath composition for hard Fe–C alloy plating

Fairly uniform Fe–C alloy deposits with bright appearance and characteristic black colour were obtained in Hull cell tests at 1.0A from baths with the following composition: FeSO4 0.5m or higher, citric acid 0.01m or lower, and pH around 2.0. The carbon content of the deposits from these baths ranged between 1.0 and 1.2wt% and the Vickers hardness was HV700 or above over a wide area of the Hull cell cathode. The thickness distribution of the deposits on the Hull cell cathode from these baths suggested that the current efficiency was 100% and the local current density obeyed the primary current distribution, except for the region near the low-current-density (LCD) end where the thickness decreased unexpectedly. The addition of chloride ion as NaCl, at concentrations of 1.0m or above, improved the thickness in the LCD region, and the thickness distribution on the Hull cell cathode suggested that current efficiency was 100% even at the LCD end. Chloride ion did no t affect the carbon content or the hardness of the deposits. Polarization measurements showed that the hydrogen ion reduction occurred at more noble potentials than Fe deposition. The unexpected thickness decrease near the LCD end, observed in Hull cell tests, and the improvement of this by adding chloride ion were both accounted for by the change in the preceding hydrogen ion reduction rate. The increase in citric acid concentration enhanced hydrogen ion reduction and therefore caused a lowering of current efficiency at low current densities. On the other hand, the addition of chloride ion inhibited hydrogen ion reduction and caused an increase in current efficiency at low current density.     

Recovery of deuterium from hydrogen–deuterium mixture using palladium

The applicability of palladium for the separation of hydrogen isotopes (hydrogen and deuterium) is evaluated systematically by generating isotherm data and conducting column experiments in a laboratory set-up. Effect of various parameters such as concentration of the isotopic mixture, particle size, eluent flow rate, etc. is studied experimentally. A fixed-bed chromatographic model is developed and validated using the experimental data. The model is further used to predict the performance of a multi-column configuration for large-scale separation. Chromatographic separation is thus found to be a promising technique to achieve the required purity and hence it may be clubbed with the existing systems (e.g. cryogenic distillation) to obtain enhanced performance.     

Synthesis and fluorescence properties of a waterborne polyurethane–acrylic hybrid polymeric dye

A waterborne polyurethane–acrylic hybrid polymeric dye was prepared depending on soap-free emulsion polymerization method. The resulting polymeric dye composed of methyl methacrylate (MMA) monomer which was polymerized into polymethyl methacrylate (PMMA) as cores and waterborne polyurethane-based dye was synthesized by anchoring dye monomers (6-amino-2-cyclohexyl-benz[de]isoquinone-1,3-dione) to polyurethane chains as shells. The average particle sizes of the hybrid polymeric dye emulsions were found to be increased with the increase in MMA contents for MMA monomers. Compared with dye monomers, the absorption intensities and fluorescence intensities of the hybrid polymeric dye were enhanced with the increase of particle sizes. This study revealed that enhanced fluorescence intensity of the hybrid polymeric dye was mainly attributed to the hindered formation of exciplexes among dye monomers and an augmented light absorption area. It was found that the fluorescence intensity of the hybrid polymeric dye was increased with increasing temperature and the trend first increased and then decreased with increase in concentration. Furthermore, the fluorescence of the hybrid polymeric dye emulsions was found to be very stable and not sensitive to the fluorescence quencher.     

Preparation and characterization of water-based polyurethane–acrylic hybrid nanocomposite emulsion based on a new silane-containing acrylic macromonomer

A new silane-containing acrylic macromonomer, maleimidedoethoxybutoxydimethylsiloxy butyl acrylate (MEBDMSBA), based on maleic anhydride (MA), ethanolamine (EA), 1,4-butanediol (BDO), dichlorodimethylsilane (DCDMS), and acrylic acid (AA) has been synthesized for formulation of waterborne polyurethane (WPU). Also a series of new silane-containing WPU, methyl methacrylate (MMA), MEBDMSBA, and montmorillonite (MMT) with organically modified montmorillonite (OMMT) content (1.25 wt%) hybrid nanocomposites have been successfully prepared by the emulsion polymerization in the presence of a WPU dispersion, using ammonium peroxodisulfate (APS) as an initiator. The WPU dispersion has been synthesized by a polyaddition reaction of isophorone diisocyanate (IPDI) on polypropylene glycol (PPG-1000) and dimethylol propionic acid (DMPA) as chain extender. The monomer was characterized by Fourier transformer infrared spectroscopy (FTIR), elemental analysis, proton (¹H NMR), and carbon (¹³C NMR) nuclear magnetic resonance spectroscopes, respectively. The nanocomposite emulsions were also characterized using Fourier transform infrared spectroscopy (FTIR) and laser light scattering. Thermal properties of the copolymers were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The OMMT was characterized by FTIR and X-ray diffraction (XRD). The morphology of copolymers was investigated by scanning electron microscopy (SEM) and transition electron microscopy (TEM), and then the effects of silane concentrations on the water absorption ratio were examined. Results showed that OMMT could improve the properties of emulsion; in other words, the properties of nanocomposite emulsion were better when compared with those of the silane–acrylate emulsion.     

Influence of ingredients in water-based polyurethane–acrylic hybrid latexes on latex properties

Polyurethane–acrylic (PU–AC) hybrid latexes were prepared. Main monomers for PU preparation were isophorone diisocyanate, DMPA (dimethylol propanic acid) and polypropylene oxides (PPO) of different molecular weights. Acrylic monomers included butyl acrylate, methyl methacrylate and a crosslinker, trihydroxymethyl propane triacrylates (TMPTA). Several important ingredients in PU–AC latex preparation, such as surfactants, initiator, DMPA and PU/AC ratio, etc., were varied, and their effects on latex properties studied. Compared with surfactant free latexes, a sharp increase in particle size was observed in latexes done with 0.1% of surfactant regardless of the nature of the surfactants used (anionic, nonionic and anionic with long chain of amphiphilic alkylphenyl polyethoxylate). Further increase in surfactant content, however, led to latexes with smaller particle size and narrower particle size distribution when compared between latexes prepared using a same surfactant. When amount of the oil soluble initiator, azobisisobutyronitrile, was increased, AC monomers conversion was increased. It is interesting to observe that PPO with long propylene oxides brought about larger particle size combined with broader size distribution and less charge on particle surface; whereas lower DMPA levels led to latexes also of larger size combined with broader size distribution but more charges on particle surface. AC monomer crosslinker, TMPTA, contributed to reduce particle size, narrower size distribution and lower particle surface charges. By increasing AC amount in PU–AC latex, latex particle size significantly increased accompanied by a remarkable increase in particle surface charges. Mechanisms of particle formation and of DMPA stabilization were discussed in order to understand the experimental results.     

Optimization and modeling of the performance of polydimethylsiloxane for pervaporation of ethanol−water mixture

Response surface methodology was used to optimize the performance of pervaporation of ethanol aqueous solution using polydimethylsiloxane hollow-fiber membrane. The effects of four operating conditions, that is, the feed temperature (30–50°C), the feed flow rate (10–50 L/h), ethanol concentration (5–20 wt%), and the vacuum pressure (10–50 KPa) on the membrane selectivity and the total flux of permeation were investigated with response surface methodology. The results showed that a quadratic model was suggested for both selectivity and total flux showing a high accuracy with R² = 0.9999 and 0.9995, respectively. The developed models indicated a significant effect of the four studied factors on both selectivity and total flux with some significant interactions between these factors. The optimum selectivity was 15.56, achieved for a feed temperature of 30°C, feed flow rate of 10 L/h, ethanol concentration of 15 wt%, and a permeate pressure of 10.74 KPa whereas the optimum total flux was 1833.66 g/m².h was observed for at a feed temperature of 50°C, a feed flow rate of 50 L/h, ethanol concentration of 15 wt%, and a permeate pressure of 49.38 KPa.     

Coagulation–bubbling–ultrafiltration: Effect of floc properties on the performance of the hybrid process

A novel hybrid process of coagulation–bubbling–ultrafiltration was proposed to study membrane fouling phenomena by surface water. Relationship of bubbles, flocs and the hollow fibers was explored. When applying less than 20 mL/min gas flow rate, membrane fouling was accelerated with air bubbles introduced. When gas flow rate increased further to 40 mL/min and 60 mL/min, TMP showed a two-stage development trend, which was a fast development in the first few hours followed with a relatively slow development after about 4 h. Unified membrane fouling index (UMFI) increased from 0.00216 (without bubbles) to 0.00274 m²/L (40 mL/min gas flow rate) and 0.00219 m²/L (60 mL/min gas flow rate). As gas flow rate increased, bubble size became bigger, and its distribution range became wider, resulting in higher shear rate in the ultrafiltration column, which led to severe floc breakage. Flocs of small size and compact structure accelerated membrane fouling, resulting in highest UMFI value under 40 mL/min gas flow rate. However, under 60 mL/min gas flow rate, with largest bubbles and highest shear rate examined in this study, concentration polarization was effectively limited. As a result, TMP development slowed down when pore blockage reached equilibrium.     

Optimization of wear–corrosion properties of a–C:N films using filtered cathodic arc deposition

Applying a 4-factor (negative substrate bias voltage, arc current, Ar flow and N₂/Ar ratio) 3-level (L9) orthogonal array design using the Taguchi method to optimize the wear–corrosion properties of a–C:N in Filtered Cathodic Vacuum Arc (FCVA) deposition was investigated. The influence of N₂/Ar ratio, over the range of 1/6 to 2/3, is shown by the increase in the following: the wear–corrosion current density changes from 36 to 78 nA/cm², and the friction coefficient changes from 0.042 to 0.086. A higher N₂/Ar ratio induces the a–C:N film's structure to reduce the sp³ content (sp² rich) which implies the formation of loose networks due to N₂ incorporation. Based on the analysis, the N₂/Ar ratio is the most significant control factor as its percentage contribution is 69% for wear–corrosion current density and 32% for frictional coefficient, respectively. There is a tendency for a higher friction coefficient by increasing the following three factors; level of negative substrate bias voltage, Ar flow and N₂/Ar ratio. We observed an increase of N content and sp² bonding which correlated to the decrease of hardness and an also rougher a–C:N surface with increasing the factors level. Over the design range of 4 factors, the optimum wear–corrosion properties and friction coefficient obtained from the Taguchi analysis were obtained using a 20 V negative substrate bias, 30 A arc current, 30 sccm Ar flow and 1/6 N₂/Ar ratio respectively. Overall, the results show an optimum design when compared with the current design as it was able to reduce 84% of the wear–corrosion current density (35.7 down to 5.6 nA/cm²) and 58% of the frictional coefficient (0.060 down to 0.025), respectively.     

Synthesis and properties of Ricinodendron heudelotii oil based hybrid alkyd–acrylate latexes via miniemulsion polymerization

Ricinodendron heudelotii (R. heudelotii) oil-based novel alkyd–acrylate hybrid latexes were synthesized as waterborne environmental friendly binder for coating systems. Long oil length alkyd resins were synthesized by two-stage alcoholysis–polyesterification reaction with variation of phthalic anhydride (PA) and maleic anhydride (MAH) proportion and further polymerized with methyl methacrylate (MMA) and butyl acrylate (BA) via miniemulsion polymerization. It is found that increasing the proportion of MAH in the alkyd resin enhances monomer conversion and total solid content of the hybrid latex. The latexes exhibited fast drying time at room temperature. The prepared latexes showed a bimodal particle size distribution motion. It is shown that the increase in MAH content in the alkyd moiety has a significant effect on the improved performance properties of hybrid latexes as well as latex films including, fast drying time at room temperature, highly crosslinked network, improved mechanical characteristics before and after UV exposure, better shore A hardness and hydrophobic water repellency contact angle. The results suggested that, the R. heudelotii oil-based alkyd–acrylate hybrid latexes have potential improved properties for manufacture of waterborne coatings and are usable as an alternative to petroleum-based coating systems.     

Effects of the air–steam mixture on the permeability of damaged concrete

Massive concrete structures such as the containments of nuclear power plant must maintain their tightness at any circumstances to prevent the escape of radioactive fission products into the environment. In the event of an accident like a Loss of Coolant Accident (LOCA), the concrete wall is submitted to both hydric and mechanical loadings. A new experimental device reproducing these extreme conditions (water vapor transfer, 140 °C and 5 bars) is developed in the GeM Laboratory to determine the effect of the saturation degree, the mechanical loading and the flowing fluid type on the concrete transfer properties. The experimental tests show that the previous parameters significantly affect the concrete permeability and the gas leakage rate. Their evolution as a function of the mechanical loading is characterized by two phases that are directly related to concrete microstructure and crack development.