داود زارعی

Epoxy thermoset resins have been used in the composite, construction, electronics, adhesive and coatings industries due to their good thermal, electrical and chemical properties. Distribution and dispersion of nanoparticles in polymer matrix is an important and influential issue in the mechanical properties of epoxy nanocomposites. Curing kinetics equations are used to evaluate and optimize the production process, and degradation kinetics modeling has become widely used as an essential tool for engineers to reduce costs and product quality. Addition of modified carboxyl and amine groups to pure epoxy resin does not change the curing reaction mechanism and also modifying the surface of nanodiamond increases the curing rate of epoxy nanocomposite. Investigation of hybrid thermal stability of epoxy nanocomposites in the presence of nanodiamonds and graphene oxide showed that the simultaneous presence of two different types of nano material can increase the thermal stability. In this research, the effect of adding nano diamonds and modified nano diamonds on morphology, mechanical and rheological properties, and modeling of curing kinetics and degradation kinetics and tribological properties have been investigated.

Epoxy resin has been used as can coating material for decades because of its suitable chemical and mechanical properties compared to the other resins. Recently, usage of this resin has been limited due to the migration of Bisphenol A (BPA) derivatives into the foodstuffs. Different solutions have been proposed to solve this problem, but so far, no suitable, comprehensive and comprehensive answer has been provided. In the current study, coating material containing mixed polyester and epoxy resins with different amounts of nano-silica particles, using Taguchi experimental design method, were prepared. The formulated coating materials were cured in the presence of melamine formaldehyde resin. The mechanical and chemical properties of cured coatings were investigated based on the EN1186-EU 10:2011 standard method. Migration tests containing global migration and BPA migration were performed, and also toxicity assessment showed that the concentrations of released materials into the food simulants were in the acceptable ranges, based on the above-mentioned standard. Also, the results showed that the polyester resin can be a suitable structure for can coatings and replacing it with epoxy resin, up to about 47%, and the presence of silica nanoparticles (about 0.5 wt%), leads to synergistic effects and increases the barrier and protective properties of the modified coatings.

Silicone rubber (SR) is a high voltage insulation coating, but has poor mechanical properties. Adding nanoparticles is a promising way to deal with this problem. In this study, evaluation of the presence of SiO2, Al2O3, MgO and SiC nanoparticles in the amounts of 0, 2, 4 and 6% by weight in the structure of silicone rubber was done through the distribution of particles within the silicon matrix and simultaneous curing. Mechanical electrical and dynamic-mechanical thermal analysis tests were performed to study the behavior of the prepared samples. Results showed that the presence of nanoparticles even in small amounts increased the strength and elongation at break and the only exception in this regard was the presence of SiC nanoparticles at 4 and 6% by weight in which a decrease in this property was observed. The electrical resistance of SR increased with the mixing of small amounts of nanoparticles. The results of polarization tests showed that the addition of SiC reduced the polarization current to about 200 pA compared to other samples. Dielectric breakdown test showed that the structures containing SiO2 and Al2O3 and 2% SiC nanoparticles had the highest dielectric strength. Dynamic-mechanical thermal analysis tests also showed that the storage modulus and glass transition temperature of the resulting nanocomposites increased up to 7 MPa and about 50 ° C, respectively, The thermogravimetric analysis showed a 100 ° C increase in the degradation temperature and as a result, the thermal stability of the nanocomposites was superior to that of pure silicon.

Epoxy resins are one of the most important thermosetting polymers that applied in the industries of coatings, buildings, and high performance composite materials due to their physical , mechanical properties and good chemical resistance. Curing kinetics equations are used to optimized epoxy resins and epoxy nanocomposites and also, studying the kinetics of curing can increased the quality of the final product. Changes in the glass transition temperature can affected the conversion of the epoxy resin, and the presence of carbon nanofibers in the matrix helps to improved the crosslinking process. Adsorption of curing agent molecules into carbon nanofibers reduced the concentration of carbon nanofibers and also, surface modification of nanofibers reduced the activation energy and improved the curing rate. In this research, the effect of adding carbon nanofibers and modified carbon nanofibers on morphology and mechanical , rheological properties, activation energy, reaction rate, degree of curing, heat flow, and curing kinetics modeling has been investigated.

In this study, the effect of elastomeric nanoparticles on the thermal and cure kinetic behavior of epoxy resin was investigated. The thermal behavior of epoxy resins and epoxy nanocomposites were investigated at three different temperatures of 65, 70, and 75 oC under isothermal conditions . For this purpose, scanning electron microscopy and differential scanning calorimeter tests were used. Morphological examination of epoxy nanocomposites showed that the appearance of elastomeric nanoparticles is spherical and shows good dispersion in the epoxy matrix at both 0.5% and 1%.Examination of the heat flow of epoxy resin and epoxy nanocomposite showed that it initially increases and decreases after reaching a maximum point and by adding elastomeric nanoparticles the degree of curing, the total enthalpy of the reaction and the peak heat flow time increased .Curing kinetics modeling showed that epoxy resin and epoxy nanocomposites follow the nth-order model and with increasing the presence of elastomeric nanoparticles, the activation energy decreased and this type of nanoparticles plays a catalytic role in reaction with epoxy resin and laboratory data are in good agreement with the results of curing kinetics modeling.

In this research, the thermal stability and thermal degradation of epoxy resin in the presence of different amounts (0,0.5,11.5) by weight percent of elastomeric nanoparticles have been investigated using Thermal Gravimetric Analysis. The results of derivative thermogravimetrically analysis (DTG), showed that at constant heating rate, by adding 0.5 and 1 wt% of elastomeric nanoparticles to the epoxy resin matrix, the maxi- mum degradation temperature increases and the mechanism of thermal degradation of epoxy resin and epoxy nanocomposites was single step. 1% nanocomposite sample showed highest maximum degradation temperature and also with increasing the heating rate, the temperature of 95% degradation (T95)of pure epoxy resin and epoxy nanocomposite samples increased . On the other hand ,this temperature for 1.5% and 0.5 and 1% nanocomposites was decreased at first and then increased. The activation energy was evaluated with the models of Augis, Ozawa, Horowitz-Metzger, and Friedman, and the results showed that the models of Augis and Ozawa behave similarly to each other. Examination of the master curve of epoxy nanocomposites showed that by adding 0.5 and 1 wt% of elastomeric nanoparticles to the epoxy resin matrix, the degradation reaction mechanism becomes A4.

In this study, self-stratified metallic surface coating based on polyurethane resin consisting of single-layer polymer acrylic with high gloss, without the use of clear coat, with the aim of covering industrial parts, home appliances and even car body repair was designed and formulated. The purpose of the work was to reduce the amount of consumables, work error and coverage time compared to the conventional and traditional coating (two layers of coating consisting of metallic base coat and clear coat). To design the experiments (DOE), the Taguchi method was used to optimize the type and amount of the main raw materials, including polyol acrylic resin type, cellulose acetate butyrate and wax. Various tests such as adhesion, gloss, hardness, abrasion salt fog and immersion were performed on the formulated coatings. The results showed, for example, an optimal adhesion rate of (5B), a gloss about 89%, mottling level of 51, and hardness of 210 seconds. Also, no sedimentation was observed in the liquid state and the results of moisture resistance and water immersion tests were acceptable based on standard criteria, compared to conventional double-layered samples.

Reinforced concrete shear walls are frequently used as lateral load resisting systems because of their ductile response and very good energy dissipation. When openings in RC shear walls are used due to architectural requirements, coupling beams are forming to connect two adjacent walls. The behavior of coupled shear walls is governed by coupling beams and they are the most vulnerable parts of coupled shear wall systems and were seriously damaged due to severe past earthquakes. To avoid construction difficulties and huge size of the RC coupling beams and better seismic performance an ductility, steel coupling beams in reinforced concrete shear walls have been mostly used during last years. Steel coupling beams connections to concrete shear walls are vulnerable and it is practically difficult and economically waste to repair damaged coupling beams, which would cause the building life cycle cost increasing. Therefore, it is necessary to transform traditional design approach to a design method in which some important parts would be replaceable rather than repairable. In this paper a building with special shear walls with steel coupling beams as lateral force resisting system is designed based on Iranian Standard 2800 and Iranian National Building Code. One of the 5th to 8th floor steel coupling beams section considered as fuse element and side beams and stiffeners of I-shaped beams designed based on eccentrically braced frames link beam criteria of Iranian National Building Code (part 10). Experimental specimen containing two RC shear walls that connected to each other with designed replaceable steel coupling beam in 1 to 3 scale is constructed and assembled in strong floor lab. For providing one degree of freedom movement of load wall four TBI Motion Company TRH65VE linear supports used. Cyclic displacement history of experiment calculated based on story drift and amplitudes of loading determined using Iranian Standard 2800 limit for story drift. Based on experimental results side beams remained in the border of elastic range and inelastic behavior of system concentrated in fuse element so the goal of system is satisfied. The side beam section is stronger and different with that was obtained from link beam criteria of Iranian National Building Code (part 10) because of available steel sheet size and since the side beam force is almost equal to elastic capacity of beam, the criteria for designing side beams is modified. Total system stiffness and fuse beam stiffness that obtained from experiment are fewer than analytical stiffness of system and fuse beam. Stiffness degradation of system occurs due to partially fixed performance of steel coupling beam connection to RC shear wall and micro cracks of wall in the connection zone. Different between real and analytical stiffness of system is very important and it is necessary to repeat the building design with modified stiffness and recalculate story drifts and distributed forces in structural elements. In this paper modifying method of stiffness is developed with moving fixed end point of steel coupling beam and increase of beam length. Effective fixed point of beam is defined by adding a portion of embedment length of steel beam in RC shear wall to both steel coupling beam ends.

Plastisols are the liquid suspension compositions containing polyvinyl chloride resin (PVC), plasticizers and extenders, with various applications such as automobile coatings as seam sealers, which converts to the flexible material using heat. Rheological and mechanical properties of these compositions are related to the type of reinforcing materials. Reinforcing materials like nano silica has been used for improvement of different properties of these compositions. In this research, using Taguchi method and optimized model calculated from experimental design, effect of PVC type, particle size of calcium carbonate, type of plasticizer and silica particle size on mechanical and rheological properties like viscosity, strength, hardness and morphology were investigated. Particle size was evaluated using scanning electron microscopy and the results were analyzed. Based on variance analysis, it was found that for reaching to the optimum process conditions and highest strength of plastisol coatings, K-value for PVC resin must be about 70, mesh size of calcium carbonate about 1000, type of plasticizer was dibutyl phthalate (DBP) and nano silica particle size was about 200 nm.

In this study, sodium montmorillonite clay (Na+-MMT) nanoparticles were surface modified by azole corrosion inhibitors such as 2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBI) through ionic exchange reaction and used as anti-corrosion nanopigments inside epoxy resin. Small angle x-ray scattering (SAXS) and transmission electron microscope (TEM) tests were used to evaluate the distribution of hybrid nanopigments within the matrix of coating and the structural morphology of the compounds was investigated by scanning electron microscopy (SEM) test. Electrochemical impedance spectroscopy (EIS) and salt spray were also implemented to study the corrosion behavior of nano coatings in the corrosive environment of 3.5% sodium chloride solution. Additionally, contact angle measurement was used to evaluate the levels of hydrophilicity and hydrophobicity of steel surfaces coated with and without clay compounds optimized with azole compounds. The results indicated that epoxy coating containing 3 wt. % of MMT+MBT nanopigment, compared to epoxy coating containing 3 wt. % MMT+MBI and pure epoxy coating had higher anti-corrosion performance after 60 days of immersion in the above-mentioned corrosive environment and presence of this nanopigment led to an increase of the level of hydrophobicity in the related surface.

In this research, Micaceous Iron Oxide pigments in different ratios were added to a synthetic rubber primer. Coatings were applied on carbon steel (St 37) plates and 8 inch pipe samples. Corrosion behavior of the primers was investigated by use of Electrochemical Impedance Spectroscopy. In addition, in order to investigate the effects of Micaceous Iron Oxide pigments on the adhesion of the primer to steel substrate, cross-cut test has been corried out on carbon steel substrate. Also the adhesion of synthetic rubber tape to the primer has been investigated by peel adhesion through hanging mass method test on pipeline. Scanning electron microscopy was used to investigate dispersion condition of Micaceous Iron Oxide particles in the binder. The Electrochemical Impedance Spectroscopy results indicated that the BRP 5, (containing 5% wt. of Micaceous Iron Oxide particles) BRP 10 and BRP 15 sample has better performance than neat primer. BRP 10 sample has the best barrier effect on corrosion performance. Results of Peel adhesion test indicate that adhesion to cold applied tape for BRP 10 sample has better than neat primer.

Abstract Growth of algae and seaweed via creation of bio films or bio fouling on the surfaces leads to different problems. Different methods have been used for controlling the bio fouling so knowing and evaluation of these methods and assessment and analyzing of their benefits and disadvantages are necessary. In this article, different anti fouling coatings containing nontoxic biocides and also coatings containing nano materials, have been studied and a prospective about the using of these materials in the future have been presented.

Organic zinc-rich epoxy coating serves a range of industries over the years have raised and satisfactory performance . Micaceous iron oxide (MIO) pigments are widely used in anti-corrosion coating performance is barrier. In The research, the zinc-rich epoxy paint splvent –based formulations and their application on carbon steel panels were studied and compared with the standard 5 to 40 percent of zinc dust was replaced by MIO. The coatings were applied on low carbon steel panels and the coatings was evaluated using adhesion , cupping , impact , conical bending , hardness , methyl ethyl ketone rub test , also optical microscopy , electrochemical impedance spectroscopy (EIS) , open circuit potential (OCP) measurements and salt fog tests were used for electrochemical evaluation of coared panelsoptical microscopy was used for obsering the dispesion of MIO pigments in coatings results revealed that the coating with 40 % of zinc replaced by MIO showed better mechanical properties and greater corrosion resistance than the other samples . Overall results showed that more replacement of zinc with MIO up to 40% led to decrese the coating reactivity and increased the time of cathodic protection about 40%. .

Invar alloy (64% Fe & 36%Ni) has low coefficient of thermal expansion (CTE). Invar’s CTE is the lowest of any metal. This alloy is Iron based, so it can be corroded and need protection from corrosive species. In this research, corrosion prevention of Invar by inorganic surface coatings was investigated. Protective influences of electroless nickel plating, electroless nickel/zinc plating double layer, and zinc rich ethyl silicate coatings were studied. Electrochemical polarization test and Tafel extrapolation were used to characterize the corrosion behavior of each specimen. Results showed that the corrosion current density (icorr) of bare Invar was about 4.08 μA/cm2 and the electroless nickel coating could not decrease icorr of Invar, suitably. In addition, the specimen with electroless nickel/zinc coating showed low icorr about 5.30×10-2 μA/cm2. Also, with zinc rich ethyl silicate, the corrosion protection mechanism was cathodic and after 20 days, it changed to barrier mechanism with icorr about 6.71×10-2 μA/cm2 in icorr in 3.5% wt sodium chloride solution.

During the recent half century، using of inorganic zinc-rich coatings has been one of the efficient methods to prevent corrosion of steel structures in corrosive atmospheres. Micaceous iron oxide (MIO) is one of the most widely used pigments for anticorrosive barrier coatings. In the present study waterborne zinc-rich silicate coatings were formulated based on nanosilica-modified potassium silicate and different contents of zinc and micaceous iron oxide (MIO). After being applied on steel panels، the coatings were subjected to atomic force microscopy (AFM)، electrochemical impedance spectroscopy (EIS)، corrosion potential measurements and salt spray test. Replacement of zinc by MIO in the formulation of zinc-rich paints was revealed to shorten the duration of cathodic protection stage while on the other hand gave satisfactory results in salt spray test. It was concluded that MIO pigments can be used to control the reactivity of zinc-rich silicate coatings.

Polyurethane-clay nanocomposites were prepared by applying high-intensity ultrasound during the synthesis of clay-urethane nanocomposites. In this article, rheological measurements along with turbidimetry, optical microscopy, X ray diffraction (XRD)and Transmission electron microscope (TEM) analyses were carried out. The results of XRD showed that the distances between silicate layers of clay reached to 41 A0 in the polymeric matrix. Results showed that nanocomposites had higher dynamic moduli, and solid like behavior in comparison to that of neat polyurethane. The strong increase in modulus of nanocomposites was due to the intercalated and dispersed silicate platelets. The increase rate in storage modulus of these composites decreased at higher organoclay loadings and was not linear. Also, the sample that contained 5% organic clay showed a shear thinning behavior at low frequencies. By using the results of XRD, optical microscopy and rheometery analysis, the state of dispersion and optimum percent of clay that has the best dispersion state were obtained. J. Color Sci. Tech. 3(2009), 89-96.© Institute for Color Science and Technology.