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In this work, the water uptake of crosslinked urethane-based coatings in high humidity conditions as a function of crosslinking temperature was investigated. The water uptake values were measured using an electrochemical impedance spectroscopy technique by applying the Brasher-Kingsbury procedure. Water uptake values as high as 200% were observed in the current research. These anomalous results were explained based on capillary condensation of diffused water molecules in the nano-metrically (or nano-scale) rough hydrophilic surfaces of the pores formed by thermal degradation of the polyurethane network. The water uptake value is at its minimum when an effectively pore-free tight network formed at moderate crosslinking conditions. [ABSTRACT FROM AUTHOR]

Two different approaches were used to modify a UV-curing resin based on polyester chemistry, namely molecular and nano-particular approaches. In the molecular approach a hydrophobic compound, glycidyl neodecanoate, was reacted with the resin and was fixed on the polymer backbone. In the nano-particular approach a nano-clay was used to modify the resin in a physical manner. The electrochemical properties of the coating films were investigated using electrochemical impedance spectroscopy. In all cases a broadening of the complex plane graph in the direction of real impedance axis was observed. It was necessary in all cases to incorporate a finite length warburg element into the equivalent circuit to account for this broadening effect. The presence of this element was attributed to an intermediate case of anomalous diffusion of charge carriers through the dense polymeric network of the UV-cured films. EIS investigations of the UV-cured films show that both molecular and nano-particular modifications cause the electrochemical properties of the film to remain constant for a longer immersion time compared to unmodified resin. [ABSTRACT FROM AUTHOR]

In this investigation nano-zinc oxide-containing polyurethane-based coatings were prepared by incorporating 3 wt% nano-ZnO in the electrocoating composition. The paint films were deposited on phosphated steel panels through electrodeposition. The films were then rinsed by DI water and baked for 20 min at 165 °C in an electrical laboratory oven. The cured films were exposed to ultraviolet (UV) radiation under humid condition. Variation of chemical nature, color, surface roughness, gloss, and corrosion resistance of the coatings were investigated as a function of UV exposure period. It was found that in presence of nano-ZnO particles, photodegradation reactions of the aromatic polyurethane network are delayed for a longer time. Specular gloss and surface roughness values of the exposed films are in accordance to this observation too. It was found that deep cracks are formed in the films in which no nano-ZnO is present. The higher electrical resistance value of the nano-ZnO stabilized films was found to be due to the protective effect of the particles against photodegradation of the polyurethane binder. [ABSTRACT FROM AUTHOR]

The present work attempts to study the mechanical properties and toughness behavior of a typical acrylic melamine clearcoat modified by a polyester-amide hyperbranched polymer (HBP). Formulations were such that 0, 5, 10, 25 and 50% (molar percent) of total acrylic hydroxyl groups were stoichiometrically substituted by those of HBP. Bulk and surface of the clearcoats were studied by various mechanical techniques including hardness, tensile, dynamic mechanical thermal analysis (DMTA), nano-indentation and scratch tests. In addition a scanning electron microscope (SEM) was utilized to observe the morphology of the fractured films. The bulk mechanical properties showed that a low loading (5 molar %) of HBP was sufficient to considerably increase the bulk hardness, cross-linking density and toughness. DMTA and SEM results proved the occurrence of a single-phase blend and that the shear deformation was the main toughening mechanism of HBP modified clearcoats. In general, it was revealed that the HBP not only could act as an excellent compatible toughening agent, but also maintained the clarity of the clearcoat and increased its scratch resistance. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, the addition of silane treated TiO nanoparticles on the self-cleaning properties of an acrylic facade coating was evaluated. Tetraethoxyorthosilicate, TEOS, was used for surface treatment of TiO nanoparticles. The silica grafting on the TiO nanoparticles was characterized via Fourier Transform Infrared spectroscopy, specific surface area measurement, pore size distribution, and real density measurements. The effect of surface treatment and content of nanoparticles on the photocatalytic activity of acrylic coating and self-cleaning properties was studied. For this purpose, the photodegradation of Rhodamine B (Rh.B) dyestuff, as a colorant model, was investigated by colorimetric technique, while the coating samples were exposed to UVA irradiation. Performance of the acrylic coating films was evaluated by gloss change during accelerated weathering conditions. Also, the surface morphology of the coating films was studied using SEM analysis. The results showed that the addition of both treated and untreated TiO nanoparticles provides self-cleaning property to the acrylic coatings. However, silica surface treatment of TiO nanoparticles reduces the coating degradation caused by TiO. This is more evident when higher concentrations of the treated TiO nanoparticles are used. [ABSTRACT FROM AUTHOR]

Comb polycarboxylic acid dispersants (CPCADs) graft acrylic copolymers which consist of hanging methoxy polyethylene glycol chains and carboxylic acid groups on main acrylic chain. The CPCADs have been synthesized by radical polymerization of methacrylic acid and methoxy polyethylene glycol methacrylate as a nonionic unsaturated hydrophilic macromonomer. The CPCADs are polymeric surfactants that can be used as anionic dispersant. Methoxy polyethylene glycol methacrylate has been synthesized by esterification of methacrylic acid and methoxy polyethylene glycol in the presence of methanesulfonic acid as catalyst. These have been characterized with 1H-NMR and GPC. Acid values of CPCA dispersants have been determined. The dispersion of CPCA dispersants depends on their molecular weights, length mPEG, and acid values. Dispersion of titanium dioxide in typical solvent-based paint formulation has been investigated. The physicochemical and mechanical properties of surface coatings having CPCADs such as gloss, hardness, and contrast ratio have been investigated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Abstract: Nano zinc oxide (ZnO) was co-deposited together with a cathodic electrodeposition paint onto phosphated normal steel panels. The films containing nano zinc oxide were compared with blank films regarding their stability against UV radiation. SEM micrographs show that nano-ZnO can stop the formation of cracks in the film. On the other hand, AFM, surface roughness and loss of gloss studies showed that the presence of nano zinc oxide particles reduces the photo-degradation of the aromatic polyurethane binder. It was also found that the presence of the nano-sized ZnO particles in the films reduces the tendency of the films to yellowing. [Copyright &y& Elsevier]

Abstract: Typically blocked isocyanate systems are used to obtain the performance of two component polyurethane (PU) system in a one-component mixture. In this study four types of isocyanates namely, hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI) were blocked with diethylene glycol monobutyl ether (DEGMBE). Elimination of the isocyanate groups and the formation of urethane bonds were studied by FTIR spectroscopy and titration methods. Thermal dissociation of blocked diisocyanates was analyzed by DSC and TGA techniques. Deblocking temperature obtained by DSC and TGA techniques was compared. Based on DSC data, it was found that deblocking of blocked MDI and TDI starts at lower temperatures compared to that of the aliphatic one (HDI). Reactivity of the blocked IPDI is between blocked MDI and blocked TDI. In general, TGA results show the same trend as DSC except for IPDI which shows the lowest deblocking temperature. Deblocking temperature values obtained by TGA technique were lower than DSC values. [ABSTRACT FROM AUTHOR]

Abstract: In this work different nano silica particles varying in aminosilane functionalities were dispersed into a polyurethane clear coating (PU). The optical clarity of the resulting films as well as the mechanical integrities were studied utilizing haze transmission and dynamic mechanical analysis respectively. In addition, the curing behavior of films was investigated using differential scanning calorimetry. It was found that particle dispersibility directly depended on the amount of grafted silane at the surface of nano silicas. Also the presence of amine functional groups on silica particles resulted in a systematic improvement of Tg and therefore in enhanced mechanical performance. These were attributed to an increased interfacial interaction and formation of some urea linkages in the hard segment of the polyurethane matrix. The DSC analyses also showed that the heat of reaction of particle loaded samples were all lower than that of the blank PU due to the facilitated interaction of amino groups at the silica surface with isocyanate cross-linker. [Copyright &y& Elsevier]

Abstract: In present study, the influence of presence of nano-silica particles having different surface modifications on curing reaction of a thermosetting acrylic-melamine clear-coat is clarified. Acrylic-silica nano-composites were made by grinding and dispersing of silica nano-particles in a thermosetting acrylic resin via milling. The resulting compositions were characterized in terms of curing reaction and the final film morphology. The cure reaction of the Neat and nano-particle containing clear-coats was monitored by differential scanning calorimetry (DSC). It was found that the presence of nano-silica particles, either hydrophilic or hydrophobic, reduces the activation energy of cure and increases the total heat of reaction. The morphology of the film is also extensively influenced by the presence of nano-particles. [Copyright &y& Elsevier]

Abstract: Nano-indenter as a technique for characterization and evaluation of mar/scratch resistance of a two component automotive clear coat is used. Different responses of the coatings to the marring stress and critical forces are discussed. The plastic deformation compared to the elastic part and the damage width is decreased by adding nano-silica in the coatings formulation. [Copyright &y& Elsevier]

Estimation of adhesion durability of an epoxy coating through wet and dry cycles has been investigated. For this purpose, we endeavor to find a correlation between adhesion durability and viscoelastic parameters of coatings. An epoxy resin was cured with four types of hardeners (polyamine, polyamidoamine, polyether polyamine, and cycloaliphatic polyamine-based hardener) and a mixture of two hardeners (polyether polyamine and cycloaliphatic polyamine) in four different mixing ratios (20:80, 50:50, 70:30, 90:10) to achieve various viscoelastic properties. The storage modulus, viscoelastic creep-recovery, electrochemical parameters, and glass transition temperature were determined. Adhesion loss and recovery of adhesion were measured under wet and dry conditions during the time. It was found that creep recovery data correlated exactly with the recovery of adhesion. Creep recovery data were modeled and for the first time, two rheological parameters (viscous ratio and elastic ratio) were defined to predict adhesion durability. Pearson correlation coefficient was used as a statistical measure of the strength of a linear relationship between the paired data. It was found that adhesion durability and recovery of adhesion after wet and dry cycles have a strong linear relationship with viscous and elastic ratios. A coating with a higher viscous behavior in creep recovery tests acts more weakly in the recovery of adhesion. It may be referred to as irreversible strain in a coating that may not be recovered after the elimination of stress. • Two rheological parameters were introduced from creep recovery modeling. • The creep recovery data correlated exactly the recovery of adhesion. • Pearson correlation coefficient correlates rheological properties and adhesion sufficiently. [ABSTRACT FROM AUTHOR]

Highlights: [•] Carbon nanotubes (CNTs) with four different surface functionalities were produced. [•] Water contact angle of functionalized CNTs was varied from 40° to 142°. [•] CNT/PMMA composites with different functionality and content of CNT were prepared. [•] Surface properties of composites were affected by surface functionality of CNTs. [•] CNTs with hydrophobic surface functionalities have migrated to composite surface. [ABSTRACT FROM AUTHOR]

Abstract: Surface treatment of nanosilicas with silane coupling agents is a common method by which the interfacial interaction of these particles can be enhanced. This is because of interactions taking place between the silane and silica, as well as the interactions between the organic part of the silane with the polymeric matrix. Therefore, interfacial interaction of silane grafted silica plays a key role to ensure a better reinforcing effect. The present work is an attempt to quantitatively predict the interfacial bonding strength between differently amino silane treated nanosilicas and a polyurethane coating matrix. This was based on the data deduced from tensile strength and dynamic mechanical thermal (DMTA) experiments of differently loaded untreated and treated nanosilicas loaded films. Using a predefined linear model taking into account the yield stresses of the particle loaded polyurethane and that of the matrix itself, an interaction bonding strength parameter was obtained. It was shown that this parameter was directly proportional to the amino silane content on nanosilica. However, for higher loadings of silicas the model best fit the data deviated from linearity and obeyed a second order equation, in which the second power term attributing the extent of interfacial strength was systematically increased. These results were in good agreement with the storage modulus and glass transition temperature values revealed by DMTA analysis. [Copyright &y& Elsevier]

The present work has studied the influence of an OH-functionalized polyhedral oligomeric silsesquioxane(POSS) nano-structure on the scratch resistance of a typical acrylic melamine clearcoat. Scratch resistance and the healing ability of clearcoats were investigated by micro-scratch studies and confocal profilometry techniques. In addition, hardness and thermo-mechanical characteristics of clearcoats were investigated by micro-indentation and dynamic mechanical thermal analysis (DMTA) respectively, to correlate the scratch behavior to the mechanical and structural properties of the clearcoats. The results revealed that incorporation of POSS cages into clearcoats could effectively enhance the scratch resistance. This was attributed to the higher hardness and cross-linking density of the resulting nanocomposite coatings. The healing results also demonstrated that nanocomposites had a higher healing ability compared to the neat clearcoat. The higher healing of nanocomposites was explained by the physical H-bonding interactions formed in vicinity of POSS cages. The transparency measurements proved that these improvements were fulfilled without any negative effect on the optical quality of clearcoats. [ABSTRACT FROM AUTHOR]