Preparation of surface energy controlled automotive clearcoats loaded with functional silicon additives: Studying the resistance against tree gum attack

The aim of this study is enhancing an automotive clearcoat easy-to-clean property against simulated tree gum (Arabic gum) using hydroxyl-functional silicone polyacrylate additives having different hydroxyl contents. The clearcoat surface, mechanical and chemical properties were studied using a contact angle measuring device, dynamic mechanical thermal analysis (DMTA) and Fourier Transform Infrared spectroscopy (FT-IR) respectively. It was found that additive with lower hydroxyl content gave rise to better easy-to-clean properties of the clearcoat against Arabic gum. This additive also resulted in lower contact angles and higher cross-linking density, tensile stress and work of break of the clearcoat.     

Effect of polysiloxane additives on the scratch resistance of an acrylic melamine automotive clearcoat

Many attempts have been carried out to increase the scratch resistance of clearcoats using various appropriate additives. These additives may increase surface hardness or surface slippage, and/or enhance the bulk mechanical strength of the clearcoat. In the present study, the influence of various added loads of three differently structured polysiloxane additives on the scratch resistances of an acrylic melamine clearcoat was investigated. A series of analytical instruments, such as a laboratory carwash simulator, a scanning electron microscope, an optical microscope and an attenuated total reflectance Fourier transform infrared spectroscope, and others were used to compare the effects of the various added contents of polysiloxane additives on changes in the viscoelastic properties and scratch morphologies of the resultant clearcoats. The results illustrated that all polysiloxane additives improve the scratch resistance of such clearcoats, yet the optimum load varied for each individual additive. There is also a good indication that polyether-modified polysiloxanes improve scratch resistance by increasing surface hardness, while the fluorocarbon-modified polysiloxane tends to change the viscoelastic properties of the clearcoats. It was also found that scratch resistance varied linearly with Micro-Vickers’ hardness for brittle clearcoats.     

Evaluation of the weathering performance of basecoat/clearcoat automotive paint systems by electrochemical properties measurements

The aim of the present study was to investigate the possibility of evaluating the weathering performance of a basecoat/clearcoat automotive paint system through the determination of its electrochemical properties. To this end, the electrochemical properties of a basecoat/clearcoat automotive paint in a 3.5% solution of NaCl in deionized water were measured at different weathering exposure times. A constant phase element (CPE) was used for describing the electrochemical behavior of the coatings under test. The values of the CPE parameters, i.e. Y₀ (the CPE constant) and n (the CPE power) were subsequently correlated to the extent of photo-oxidation (as measured by appearance, surface roughness, FTIR, surface tension and adhesion measurements) of clearcoat at the surface, in the bulk and at the interface between the basecoat and the clearcoat. The result showed that the electrochemical parameters Y₀ and n provide ready means for comparing the weathering performances of basecoat/clearcoat automotive paint systems. Increases in the value of Y₀ together with decreases in the value of n with increasing weathering exposure times suggest increased possibilities for the onset of cracking in the clearcoat itself in addition to its propagation towards the basecoat. Additionally, sudden variations in the values of Y₀ and n are indicative of increases for the clearcoat to peel off.     

Studying the role of polysiloxane additives and nano-SiO2 on the mechanical properties of a typical acrylic/melamine clearcoat

Effects of conventional polysiloxane additives and nano-SiO₂ on the mechanical properties of an automotive acrylic/melamine clearcoat (CC) are studied. Clearcoats formulations were prepared by addition of different concentrations of polysioloxane additives (with different modifications) and hydrophobic nano-SiO₂ particles. Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) and atomic force microscope (AFM) were utilized to evaluate the effects of nano-SiO₂ and polysiloxane additives on the surface properties of the CCs. The mechanical properties of the surface and the bulk of the CCs were studied by nano-indentation and tensile tests, respectively. Results showed that polysiloxane additives can mostly affect the mechanical properties of the surface of the CC. Additives with shorter side chains and therefore higher surface activity caused higher changes on the surface properties the CC. Unlike conventional polysiloxane additives, the nano-SiO₂ particles mainly influenced the mechanical properties of the bulk of the CC.     

Attributing the resistance against simulated tree gum of an acrylic/melamine film loaded with an active silicone additive to its surface free energy

The present work reports preparation of acrylic/melamine based clearcoats with different loadings of a functionalized polysiloxane additive. The resulting films were applied over a black basecoat automotive coating system. Dynamic mechanical thermal analysis (DMTA), contact angle measurement, optical microscopy and gonio-spectrophotometery were utilized to investigate the mechanical (viscoelastic/viscoplastic), surface and optical properties of the coating system before and after exposure to Arabic gum (simulated tree gum). The resistance of film surface against gum attack showed high dependence on gum adhesion to the films. It was revealed that depreciation of surface free energy of additive loaded films could greatly improve their behavior against gum, apparently due to their enhanced non-stick characteristic. Tg and loss peak height also increased, indicating that additive did not negatively influence coating curing state. However, at loading contents exceeding 4 wt% both Tg and loss peak height decreased, revealing that a phase separation had occurred. The improved resistance of films against Arabic gum was corresponded to the low clearcoat shrinkage and crack formation. Weaker interactions between gum and clearcoat surface was seen in presence of additive. The shape and size of defects (of gum exposed films) were also significantly changed.     

Surface tension studies of additives in acrylic resin-based powder coatings using the Wilhelmy balance technique

A modified Wilhelmy balance technique using thin fibers as solid probes has been applied to study the effect of silicone additives in acrylic resin-based powder coatings on the surface tension of non-reactive binder systems. By measuring the temperature dependence of the surface tension in the temperature range between 140 and 180°C, it could be shown that the silicone additives investigated had a very different surface activity in the molten acrylic resin. Due to the high accuracy of the measuring technique and the good reproducibility of the experiments the influence of different additive concentrations on the surface tension was detectable even at very low concentrations (below 1 wt.%).

Compared to the pure powder coating binder which has a surface tension of about 30 mN/m the values decreased between 2–15 mN/m depending on the type of the silicone additive. In addition, the temperature coefficient −(dγ/dT) of the surface tension of the binder melt was changed. In the case of two additives, the surface tension of the powder coating and its temperature coefficient were lowered considerably. This effect of additives is desirable to reach good wetting and leveling of the powder coating.     

Influence of coalescence and interfacial tension on the morphology of PP/HDPE compatibilized blends

In this paper, the compatibilization of polypropylene (PP)/high-density polyethylene (HDPE) blend was studied through morphological and interfacial tension analysis. Three types of compatibilizers were tested: ethylene-propylene-diene copolymer (EPDM), ethylene-vinylacetate copolymer (EVA) and styrene-ethylene/butylene-styrene triblock copolymer (SEBS). The morphology of the blends was studied by scanning electron microscopy. The interfacial tension between the components of the blends was evaluated using small amplitude oscillatory shear analysis. Emulsion curves relating the average radius of the dispersed phase and the interfacial tension to the compatibilizer concentration added to the blend were obtained. It was shown that EPDM was more efficient as an emulsifier for PP/HDPE blend than EVA or SEBS. The relative role of interfacial tension reduction and coalescence reduction to particle size reduction was also addressed. It was observed that the role of coalescence reduction is small, mainly for PP/HDPE (90/10) blends compatibilized by EPDM, EVA or SEBS. The results indicated that the role of coalescence reduction to particle size reduction is lower for blends for which interfacial tension between its components is low at compatibilizer saturation.     

Effects of liquid viscosity and surface tension on atomization in two-phase, gas/liquid fluid coker nozzles

This is an experimental study of the effects of liquid viscosity (μ_L) and surface tension (γ) on the size of droplets produced by an atomizer fed with a two-phase gas/liquid (TPGL) mixture. The nozzle is a one-quarter scale model of an industrial fluid coker nozzle used for bitumen upgrading. The primary objective of this study was to compare the Sauter mean diameter of the TPGL sprays for different μ_L and γ. Compressed air was used as the gas phase; the liquid phases were water, canola oil and a glycerine-water solution. The μ_L was varied from 1 mPa s to 67 mPa s, and γ was varied from 25 mN/m to 61 mN/m. The liquid flow rates were varied from 0.095 L/s to 0.105 L/s, and the gas-to-liquid ratio , by mass, was fixed at 2%, similar to the ratio used in commercial fluid coker nozzles. Fluid mixing pressures in the test were between 400 kPa and 700 kPa. The D₃₂ within the spray was measured using a Dantec 2D-Fibre mode Phase-Doppler-Particle-Anemometer (PDPA). With measurements performed at axial distances of 100 and 202 mm from the nozzle orifice and within a spray radius of 40 mm. The results showed that the 67-fold increase in μ_L results in 46 μm increase in D₃₂ which roughly extrapolates to a power law relationship exponent of 0.11 (based on two points). In contrast, the 2.4-fold increase in γ indicates roughly 42 μm increase in D₃₂, giving an exponent of −0.24. For both parameters the exponent is small, indicating weak dependence. The γ effects appear stronger, but the modest increase is barely exceeds the margin of error.     

Surface tension prediction and thermodynamic analysis of the surface for binary solutions

The surface tensions of 100 aqueous and 200 non-aqueous binary solutions are correlated by Shereshefsky model and excellent results are obtained. The average percent deviations are about ∼1.8% for aqueous and ∼0.56% for non-aqueous binary solutions. The free energy change in the surface region is calculated and is used to obtain the excess number of molecular layers in the surface region. Furthermore, the model is used to derive an equation for the standard Gibbs energy of adsorption. Where experimental data is available for the standard Gibbs energy of adsorption, the agreement between the calculated and the experimental data is found to be very good.     

Effect of additives on the adsorption of sodium bis(2-ethyl hexyl sulfosuccinate) at the air-water interface studied by equilibrium and dynamic surface tension measurements

Using equilibrium and dynamic surface tension measurements, we have studied the effect of the addition of poly(sodium 4-styrenesulfonate) (PSS), sodium chloride, and 1,4,7,10,13,16-hexaoxyacyclooctadecane (18-crown-6) on the surface properties of sodium bis(2-ethyl hexyl sulfosuccinate) (AOT). The addition of PSS or NaCl weakly increases the maximum packing of AOT, whereas the presence of 18-crown-6 slightly decreases the maximum surface coverage. The surfactant adsorption kinetics on the interface is a diffusion-controlled process. The two asymptotic solutions at long times and at short times to the classic Ward Tordai equation were used to fit dynamic results. At long times there is evidence of the existence of an electrostatic barrier at high surfactant concentration when using pure AOT and AOT mixed with PSS. In binary mixtures of AOT with sodium chloride or 18-crown-6, the electrostatic barrier is not observed over the surfactant concentration range studied.     

Interfacial tension from the height and diameter of sessile drops and captive bubbles with an arbitrary contact angle

A method has been developed to calculate the interfacial tension of sessile drops and captive bubbles of arbitrary contact angle by measuring the drop diameter and vertical distance to the apex at arbitrary horizontal planes within the drop. The procedure works in theory for any contact angle with an accuracy on the order of 0.1%. However, practical limitations reduce the range of angles to roughly 50°–180° but do not restrict the range of interfacial tensions (at least 0.01 mJ/m² to 72.0 mJ/m²). The optimal strategy is to use the method at several points on a single drop and to calculate the mean and standard deviation of the resulting interfacial tensions.     

Interfacially compatibilized LDPE/POE blends reinforced with nanoclay: investigation of morphology,rheology and dynamic mechanical properties

Morphological, melt rheological and dynamic mechanical properties of low-density polyethylene (LDPE)/ethylene–octene copolymer (POE)/organo-montmorillonite (OMMT) nanocomposites, prepared via melt compounding were studied. The XRD traces indicated different levels of intercalated structures for the nanocomposites. Addition of a compatibilizer (PE-g-MA) improved the intercalation process. TEM results revealed existence of clay layers in both phases but they were mainly localized in the elastomeric POE phase. Addition of 5 wt% OMMT to the LDPE/POE blend led to reduction in the size of the elastomer particles confirmed by AFM. The complex viscosity and storage modulus showed little effect of the presence of the clay when no compatibilizer was added. As the extent of exfoliation increased with addition of compatibilizer, the linear viscoelastic behavior of the composites gradually changed specially at low-frequency regions. The interfacially compatibilized nanocomposites with 5 wt% OMMT had the highest melt viscosity and modulus among all the studied nanocomposites and blends. Also, this particular composition showed the best improvement in dynamic storage modulus. The results indicated that clay dispersion and interfacial adhesion, and consequently different properties of LDPE/POE/clay nanocomposites, are greatly affected by addition of compatibilizer.     

Hydrophilic modification of polypropylene microporous membranes by grafting TiO2 nanoparticles with acrylic acid groups on the surface

Hydrophilic microporous membranes were prepared based on polypropylene (PP) cast films blended with a commercial acrylic acid grafted polypropylene (PP-g-AA) via melt extrusion followed by grafting titanium dioxide (TiO₂) nanoparticles on its surface, annealing and stretching. ATR-FTIR, XPS and EDS analyses showed that the hydrophilic segments of an amphiphilic modifier (PP-g-AA) acted as surface functional groups on the film surface. The results indicated that the presence of the modifier was very important for grafting TiO₂ nanoparticles on the film surface. Compared to PP and PP/PP-g-AA blend films, the water contact angle decreased by a factor of 2.5 after grafting TiO₂ on the surface of the films, meanwhile the water vapor permeability of the microporous membranes prepared from those films increased by a factor of 1.5. All these results indicated that the hydrophilicity of the modified PP membranes was improved.     

On the thermodynamic functions of gas-solid adsorption and liquid-solid immersion,and their relation to adhesion,contact angle and surface tension

The thermodynamic functions of gas-solid adsorption and liquid-solid immersion are summarized on a literature basis. For adsorption, the isosteric and calorimetric methods are compared; for immersion, the Gibbs free energy of adhesion as a function of relative pressure is introduced.The thermodynamic functions reported are enthalpy, Gibbs free energy and entropy of adsorption, immersion and adhesion. All the formulae given contain only those values that result from adsorption, immersion, contact angle or surface tension of the liquids measurements.Interrelations between the thermodynamic functions of adsorption, immersion and adhesion are also given. They permit cross checks and substitution of measurements, e.g., of immersion for adsorption measurement.Typical values are reported and plots of some thermodynamic functions versus coverage are discussed with respect to height and decrease of the powder-adsorptive interaction with layer thickness.     

A simple and convenient method for the surface coating of TiO2 nanoparticles with bioactive chiral diacids containing different amino acids as the coupling agent

For practical applications, especially in an organic-solution situation, the surface of TiO₂ nanoparticles (NP)s requires modification with an organic coupling agent. Therefore, in this study, the surface of TiO₂ NPs with average diameter of 30 nm was modified with bioactive dicarboxylic acids (DA)s containing different natural amino acids such as l-valine, l-methionine, l-leucine, and l-isoleucine. The prepared DAs-modified TiO₂ NPs were studied with Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis techniques. The results showed that the modifiers were grafted on the surface of TiO₂ NPs. Modified TiO₂ NPs could be environmentally friendly due to the presence of bioactive DAs.     

GCMC-surface area of carbonaceous materials with N2 and Ar adsorption as an alternative to the classical BET method

In this paper we apply a new method for the determination of surface area of carbonaceous materials, using the local surface excess isotherms obtained from the Grand Canonical Monte Carlo simulation and a concept of area distribution in terms of energy well-depth of solid-fluid interaction. The range of this well-depth considered in our GCMC simulation is from 10 to 100 K, which is wide enough to cover all carbon surfaces that we dealt with (for comparison, the well-depth for perfect graphite surface is about 58 K). Having the set of local surface excess isotherms and the differential area distribution, the overall adsorption isotherm can be obtained in an integral form. Thus, given the experimental data of nitrogen or argon adsorption on a carbon material, the differential area distribution can be obtained from the inversion process, using the regularization method. The total surface area is then obtained as the area of this distribution. We test this approach with a number of data in the literature, and compare our GCMC-surface area with that obtained from the classical BET method. In general, we find that the difference between these two surface areas is about 10%, indicating the need to reliably determine the surface area with a very consistent method. We, therefore, suggest the approach of this paper as an alternative to the BET method because of the long-recognized unrealistic assumptions used in the BET theory. Beside the surface area obtained by this method, it also provides information about the differential area distribution versus the well-depth. This information could be used as a microscopic finger-print of the carbon surface. It is expected that samples prepared from different precursors and different activation conditions will have distinct finger-prints. We illustrate this with Cabot BP120, 280 and 460 samples, and the differential area distributions obtained from the adsorption of argon at 77 K and nitrogen also at 77 K have exactly the same patterns, suggesting the characteristics of this carbon.     

Synthesis and characterization of functionalized carbon nanotubes with different wetting behaviors and their influence on the wetting properties of carbon nanotubes/polymethylmethacrylate coatings

The synthesis and characterization of hydrophobic functionalized multi-wall carbon nanotubes (MWCNTs) were investigated and their influence on the wetting properties of organic coatings and composites was studied. Functionalization was performed using oxidation, 1,3-dipolar cycloaddition, and silanization. Silanization was conducted using three hydrophobic silane precursors: 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, and triethoxyoctylsilane. Functionalization was directly confirmed and characterized by Fourier transform infrared spectroscopy, thermal gravimetric analysis, and scanning electron microscopy. The water contact angle of the functionalized MWCNTs was 40–142° for different surface functionalities and the functionalized MWCNTs were incorporated into an acidic solution of polymethylmethacrylate. The effect of surface functionality and the concentration of the functionalized MWCNTs on the wetting properties of these composites were studied by measuring the water contact angle. Under optimum conditions, composite surfaces with water contact angles greater than 110° were obtained. Atomic force microscopy was used to determine the topography of the surface and energy dispersion spectroscopy was used to determine the distribution of the functionalized MWCNTs in the composite film. It was shown that the hydrophobic functionalized MWCNTs migrated to the surface; this was more pronounced for the more hydrophobic MWCNTs.     

Modification of the surface reactivity of Cu-MFI during chemisorption and transformation of the reagents in the selective reduction of NO with propane and O2

The steady-and unsteady-state catalytic behaviour of Cu-MFI in the conversion of propane and NO in the presence of O₂ is reported, showing how the chemisorption and transformation of reactants may influence the surface reactivity. Various effects were observed: (i) a change in the surface reactivity and kinetics in going from low to high concentrations of NO or propane, (ii) the transformation of NO to N₂ and N₂O promoted at low temperature (250°C) by oxygen in the absence of hydrocarbon, (iii) the influence of NO over the surface reactivity of the catalyst in the conversion of propane and (iv) the influence of surface precoverage with oxidized nitrogen oxides (N_xO_y) or carboxylate species on the catalyst transient reactivity in the reduction of NO to N₂. In particular, Cu-MFI is initially more active when oxidized nitrogen oxides are present, suggesting that the active intermediate in the reduction of NO with propane is a complex formed by the reaction of nitrate with activated hydrocarbon. It is shown, however, that strongly bound oxidized nitrogen oxides may have also additional effects on the surface reactivity: (i) can promote the conversion of NO to N₂ and N₂O in transient conditions and (ii) can give a partial inhibition of the surface reactivity blocking copper ions due to their strong chemisorption. Furthermore, it is shown that NO reacts faster with oxygen than hydrocarbon forming N_xO_y species which are then the oxidizing agent for the hydrocarbon. It is thus suggested that the surface reactivity of Cu-MFI in the reduction of NO with propane/oxygen depends on the surface population of nitrogen oxide adspecies which influence not only the surface reactivity, but also the pathway of hydrocarbon oxidation.     

Adaptation and application of the In Situ Adaptive Tabulation (ISAT) procedure to reacting flow calculations with complex surface chemistry

In this article, the In Situ Adaptive Tabulation (ISAT) procedure, originally developed for the efficient computation of homogeneous reactions in chemically reacting flows, is adapted and demonstrated for reacting flow computations with complex heterogeneous (or surface) reactions. The treatment of heterogeneous reactions within a reacting flow calculation requires solution of a set of nonlinear differential algebraic equations at boundary faces/nodes, as opposed to the solution of an initial value problem for which the original ISAT procedure was developed. The modified ISAT algorithm, referred to as ISAT-S, is coupled to a three-dimensional unstructured reacting flow solver, and strategies for maximizing efficiency without hampering accuracy and convergence are developed. These include use of multiple binary tables, use of dynamic tolerance values to control errors, and periodic deletion and/or re-creation of the binary tables. The new procedure is demonstrated for steady-state catalytic combustion of a methane-air mixture on platinum using a 24-step reaction mechanism with 19 species, and for steady-state three-way catalytic conversion using a 61-step mechanism with 34 species. Both reaction mechanisms are first tested in simple 3D channel geometry with reacting walls, and the impact of various ISAT parameters is investigated. It is found that the temperature of the reacting wall dictates the retrieval rate from the ISAT table. As a final step, the catalytic combustion mechanism is demonstrated in an laboratory-scale monolithic catalytic converter geometry with 57 channels discretized using 354,300 control volumes (4.6 million unknowns) after employing quarter symmetry. For this particular case, the use of ISAT-S resulted in reduction of the overall CPU time from 19.3 to 13.6 h. For all of the cases considered, the reduction in the time taken to perform surface chemistry calculations alone was found to be a factor of 5-11.     

西部斜坡区姚家组底界不整合面特征及其与油气运聚的关系

姚家组底界不整合面对松辽盆地西部斜坡区油气运聚具有重要意义。通过对不整合的特征系统分析,发现姚家组底界不整合面发育平行、角度不整合;纵向结构不具备典型的三层结构,底砾岩层和半风化淋滤层不发育;不整合上下岩性的配置类型以“上砂下泥”型为主。并进一步探讨了不整合的发育特征与油气运移和聚集的关系,认为角度不整合与油气运聚关系密切,并提出其发育范围内是勘探与不整合相关的圈闭有利区。