Numerical analysis of surface‐tension‐driven coating flow

Bondline readout (BLRO) is a coating defect frequently exhibited on adhesively bonded, polymeric automotive body panels painted with high‐glamour/flow clearcoats. BLRO or telegraphing results from Marangoni‐type, surface‐tension‐driven flows. The goal of this study is to use an efficient one‐dimensional numerical code (based on the lubrication approximation) to obtain further insight into the mechanism of temperature‐ and concentration‐induced BLRO flows in order to validate a proposed BRLO mechanism and ultimately to help eliminate the highly undesirable BLRO coating defect. Further insight is realized by investigating numerically the effects on BLRO of gravity and five parameters—initial film thickness, heating rate, viscosity, solvent volatility, and solvent‐to‐resin surface‐tension ratio. Possible solutions to the BLRO problem are discussed.     

Gas diffusion electrodes for high temperature PEM-type fuel cells: role of a polymer binder and method of the catalyst layer deposition

The topic of this study is the optimization of the preparation procedure and chemical composition of a gas diffusion electrode (GDE) for utilization in high-temperature PEM fuel cells. A phosphoric acid-doped polybenzimidazole derivative membrane was used as a polymer electrolyte. The following parameters were studied: nature and content of the polymeric binder (PTFE—hydrophobic, PBI—hydrophilic) in the catalytic layer (CL) and concentration of platinum in catalytic powder (affecting the thickness of the CL). Brushing and spraying were selected as the most suitable techniques of CL deposition. Surprisingly, both polymeric binders investigated in the framework of this study were found to provide a similar GDE performance for CL deposited on the gas diffusion layer surface by spraying.     

Investigation of the effect of precoalescence or postcoalescence crosslinking on film formation, properties, and latex morphology

Latexes have many product applications including functioning as a binder in coatings. For many years, coatings researchers in industry as well as in academe have been exploring various modes of crosslinking latexes. Quite often, the goal of preparing crosslinked latexes is to upgrade film properties relative to the film properties of uncrosslinked latexes. In the present report, the synthesis and properties of crosslinkable acrylic latexes prepared with either an internal crosslinker (1,3-butylene glycol dimethacrylate)—“precoalescence crosslinking”—or an external crosslinker (adipic dihydrazide)—“postcoalescence crosslinking”—at various levels of crosslinking were studied. For postcoalescence crosslinking, diacetone acrylamide was copolymerized into the latex to provide sites for subsequent reaction with adipic dihydrazide. Fundamental properties of films cast from the two types of latexes were systematically compared. These properties included gel content, dynamic mechanical properties, nano-indenter hardness and modulus, stress–strain properties as well as the characterization of latex morphology by atomic force microscopy (AFM). In addition, some specific end-use properties were determined. This study assesses the effect of type (precoalescence or postcoalescence) and level of crosslinking on the film formation process and the resulting fundamental and end-use properties as well as resulting latex film morphology. Presented at 2007 FutureCoat! Conference, sponsored by Federation of Societies for Coatings Technology, October 3–5, 2007, in Toronto, Ont., Canada.     

Changes in composition and characteristics of latex paints applied on porous inorganic substrates

Changes in film composition and characteristics that occur during and/or immediately after the application of latex paints on porous inorganic substrates were investigated. Gas chromatography (GC) and thermal analysis were among the techniques used for this purpose. The changes in coalescing agent and binder content were determined by GC and thermogravimetric-analysis, respectively, and the changes in glass transition temperature by differential scanning calo rimetry. It was found that the type of porous substrate could significantly affect the paint composition (pigment volume concentration, coalescent level) during the film formation process. Presented at the 25th FATIPEC Congress, September 2000, Torino, Italy. Are. P. Holoffe, 1342-Limelette, Belgium; email: perera.d@cori-coatings.be Leuvensesteenweg 167–199, 1800-Vilvoorde, Belgium; email: jeanmarie.borsus@akzonobel.com.     

Estimation of film thickness nonuniformity effects on coating optical properties

Film nonuniformities cause many problems for the coating scientist. One area of coating film performance that they impact directly is optical properties. Measurements and predictions of film optical performance are all made assuming uniform film thickness. Incomplete leveling and other film application problems often yield nonuniform films with significant film thickness fluctuations. These film thickness imperfections can be modeled by a sine wave thickness fluctuation, and this fluctuation can be used to estimate the effects of nonuniformity in thickness on optical properties. This has been done using both approximate equations for scattering, transmission, and reflectance in films (zero absorption) and for the Kubelka-Munk equations including absorption. the effects of average film thickness and amplitude of fluctuation on measured S, R, and T values are predicted numerically for several cases of [K, S] pairs consistent with wavelength independent situations (white or similar films) over black substrates, and then the calculations are used to consider colored films [considering δE(L*a*b*)] over black substrates. Film thickness fluctuations are shown to have considerable impact on film optical properties, especially in thin highly scattering films. Examples of the types of predictions that can be made are given; how the results depend on the coating optical parameters is also shown.     

Destruction processes in coagulation structures in vibration of coarse thixotropic corundum — Mullite — Alumina and corundum — Zircon — Alumina mixtures

Results obtained in studying the destruction processes in coagulation structures in vibration of castable thixotropic corundum — mullite — alumina and corundum — zircon — alumina mixtures containing fine alumina are presented as a function of various manufacturing parameters. General regularities and destruction mechanisms in these mixtures are established. The results are used to devise manufacturing techniques for vibrocast corundum and mullite — corundum — zircon refractories. Translated from Ogneupory, No. 8, pp. 12 – 17, August, 1994.     

Catalytic effect of solid metals on thermal stability of olive oils

The influence of a series of metals—iron, copper, tin, and lead—on the thermal stability of olive oils of different origins and refined grades has been studied by applying thermal analysis techniques: thermogravimetry (TG) and derivative thermogravimetry (DTG). From thermogravimetric data it is deduced that iron and tin have a greater influence on oil oxidation, since the degradation rate increases. In the presence of copper and lead, important changes in the degradation rate are not observed, compared with the degradation in the absence of metals. The kinetic parameters, activation energy, and frequency factor of the oil degradation reaction were also calculated. The results obtained for both parameters confirm the negative influence of iron and tin on the oil oxidation process, regardless of the kind of oil tested.     

Corrosion protection of Mg alloys by cathodic electrodeposition coating pretreated with silane

The corrosion resistance characteristics of three coatings on magnesium alloy AZ31—conventional paint with phosphate film, cathodic electrodeposition coating (E-coating), and E-coating pretreated with silane (Mg/silane/E-coating)—have been studied by means of electrochemical impedance spectroscopy (EIS) in a 3.5 wt% NaCl neutral aqueous solution and salt spray test using ASTM B117. Silane film was obtained by dipping AZ31 specimens in diluted hydroalcoholic silanic solutions and successively curing. It was found that the corrosion resistance of the Mg alloy with E-coating was superior to conventional paint and could be further enhanced with silane pretreatment as an interfacial film. The results of water volume fraction (Φ_saturation) and diffusion coefficient (D) also indicated that the Mg/silane/E-coating possessed excellent compactness and corrosion resistance. A model of the corrosion mechanism for Mg/silane/E-coating has been presented through EIS analysis.     

Preexplosion phenomena in heavy metal azides

The paper reports results of investigation of the explosive decomposition of heavy metal azides in real time. The characteristics of the detected predetonation effects — the preexplosion conductance and luminescence of heavy metal azides — are described. The obtained value of the preexplosion conductivity of silver azide indicates that the process is of a chain nature. A model for the development of explosion of heavy metal azides is developed including multiplication of active particles (holes) by a first-order reaction and chain termination by a second-order reaction. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 5, pp. 78–89, September–October, 2000. This work was supported by the Russian Foundation of Fundamental Research (Grant No. 98-03-32001a) and the Foundation of the Ministry of General and Professional Education of the Russian Federation.     

Electrocombustion of humic acid and removal of algae from aqueous solutions

This paper reports experiments involving the electrochemical combustion of humic acid (HA) and removal of algae from pond water. An electrochemical flow reactor with a boron-doped diamond film anode was used and constant current experiments were conducted in batch recirculation mode. The mass transfer characteristics of the electrochemical device were determined by voltammetric experiments in the potential region of water stability, followed by a controlled current experiment in the potential region of oxygen evolution. The average mass transfer coefficient was 5.2 × 10⁻⁵ m s⁻¹. The pond water was then processed to remove HA and algae in the conditions in which the reaction combustion occurred under mass transfer control. To this end, the mass transfer coefficient was used to estimate the initial limiting current density applied in the electrolytic experiments. As expected, all the parameters analyzed here—solution absorbance at 270 nm, total phenol concentration and total organic carbon concentration—decayed according to first-order kinetics. Since the diamond film anode successfully incinerated organic matter, the electrochemical system proved to be predictable and programmable.     

Electrochemical synthesis and characterization of poly(aniline-co-1-amino-9,10-anthraquinone), a nanosized conducting copolymer

The electrochemical copolymerization of aniline (ANI) with 1-amino-9,10-anthraquinone (1-AAQ) was carried out in 4 M sulfuric acid by potential cycling in the potential range of −0.1 V to 1.3 V vs. SCE. Copolymer films were grown from different feed ratios of ANI and 1-AAQ (0.2:0.8, 0.4:0.6, 0.5:0.5, 0.6:0.4, 0.8:0.2) on a glassy carbon electrode (GCE). Studies on the effect of scan rate on the conductivity of the copolymer film confirmed the formation of a stable conducting copolymer film. The FTIR spectrum recorded for the copolymer film provides concrete evidence of copolymer formation, since it indicates the presence of quinone units in the copolymer backbone. XRD data (particle size: 47 nm) and SEM (grain size: 100 nm) micrographs provide a clear picture of the nano-sized polymeric particles formed. It is envisaged that the newly reported copolymer could be a useful material for performing the catalytic reduction of oxygen in an acidic medium—a useful process for fuel cell applications.     

Effects of Thickness,Deformation Rate and Energy Partitioning on the Work of Fracture Parameters of uPVC Films

Summary Unplasticised poly(vinyl chloride) (uPVC) films have been tested using the essential work of fracture (EWF) method. Influence of loading rate and film thickness on the tensile properties and work of fracture parameters was evaluated. In addition, energy partition analyses were carried out applying two different approaches (“yielding” and “initiation”), which differ in the treatment of the stored elastic energy. Results showed less effect of the film thickness and deformation rate (<l00 mm/min) on the EWF terms. On the other hand, the specific essential work of fracture (w _e) at high load rate (1.2 m/s) approached the yielding-related term (w _e,y) obtained at static loading rates (<l00 mm/min). Received: 16 July 2002/Revised version: 31 March 2003/Accepted: 29 April 2003 Correspondence to M. Ll. Maspoch     

Fabrication and mechanical properties of single-wall carbon nanotubes and hyperbranched diazonium salt multilayers

Acidized single-wall carbon nanotubes (SWNTs) were fabricated into multilayers with a hyperbranched azobenzene-containing polymeric diazonium salt (PDAS) using the layer-by-layer adsorption technique. The fabrication process, multilayer thickness variation, multilayer surface morphology and the interaction between SWNTs and PDAS were monitored by UV-Vis absorption spectroscopy, optical ellipsometry, Atomic Force Microscopy, Scanning Electron Microscopy and Raman spectroscopy. Moreover, the nanomechanical properties of the multilayer films were measured by nanoindentation. All results show that SWNTs and PDAS can be fabricated into multilayers based on the cooperation of electrostatic absorption and chemical cross-linkage between SWNTs and PDAS. Further, this cooperation endows the SWNT/PDAS multilayer films with outstanding nanomechanical properties. The hardness and modulus are about 2.0GPa and 10.0GPa, respectively. Finally, the SWNT/PDAS multilayer film can be peeled off to be a free-standing film. __________ Translated from Acta Polymerica Sinica (China), 2007, (11): 1052–1056 [译自: 高分子学报]     

Film materials with controlled release of biologically active substances

The properties of spun composites containing polyvinyl alcohol, a proteolytic enzyme (protease C or Terrilytin) and the high-molecular-weight antimicrobial polyhexamethyleneguanidine hydrochloride were investigated. The effect of the composition of the spinning compositions and spinning temperature on the properties of the film materials — the activity, stability, and rate of release of biologically active substances — was investigated. The possibility of obtaining polyvinyl alcohol films with controlled release of biologically active substances was demonstrated. Translated from Khimicheskie Volokna, pp. 44–48, September–October, 1998.     

Detonation waves in a reactive supersonic flow

A supersonic hydrogen—air flow is studied in detail, in particular, the fields of gas-dynamic parameters and chemical homogeneity of the mixture in various cross sections of the duct. The processes of excitation and propagation of a detonation wave in the downstream and upstream directions are considered. The detonation-wave velocity with respect to the mixture flow is found to differ from the nominal Chapman—Jouguet velocity for a quiescent mixture: the detonation-wave velocity is higher if the wave moves upstream and lower if the wave moves downstream. Some hypotheses on the reasons for these deviations of the experimentally measured velocity from the nominal value are given. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 5, pp. 85–100, September–October, 2006.     

Penetration and distribution of α-tocopherol, α- or γ-tocotrienols applied individually onto murine skin

To evaluate skin penetration of various vitamin E homologs, a 5% solution of either α-tocopherol, α-tocotrienol, or γ-tocotrienol in polyethylene glycol was topically applied to SKH-1 hairless mice. After 0.5, 1, 2, or 4 h (n=four per time point and four per vitamin E homolog), the skin was washed, the animals killed, the skin rapidlly removed, frozen on dry ice, and a biopsy taken and sectioned: stratum corneum (two uppermost, 5-μm sections—SC1 and SC2), epidermis (next two 10μm sections—E1 and E2), papillary dermis (next 100μ, PD), dermis (next 400 μm, D), and subcutaneous fat (next 100 μm, SF). SC1 contained the highest vitamin E concentrations per μ thickness. To compare the distribution of the various vitamin E forms into the skin layers, the percentage of each form was expressed per its respective total. Most surprising was that the largest fraction of skin vitamin E following topical application was found in the deeper subcutaneous layers—the lowest layers, PD (40±15%) and D (36±15%), contained the major portion of the applied vitamin E forms. Although PD only represents about 16% of the total skin thickness, it contains sebaceous glands—lipid secretory organs, and, thus, may account for the vitamin E affinity for this layer. Hence, applied vitamin E penetrates rapidly through the skin, but the highest concentrations are found in the uppermost 5 microns.     

Instabilities induced by an electrostatic field over the film flow down an inclined plane

A study of the instabilities in the interaction of an electrostatic field with a thin liquid film flowing under gravity down an inclined plane is presented. First, the long-wave stability conditions are studied by perturbing the evolution equation of film height about its steady-state solution. Three limits of flow systems are considered, i.e., static state, Reynolds number Re = 0(1) and Re = 0(1/ξ). Here ξ(≪1) is the ratio of the characteristic length scale parallel to the flow to the primary film thickness. Next, the long-wave behavior of the thin film flow is examined with the electrostatic potential of a Gaussian function in the two limits of Reynolds number, i.e., Re = 0(1) and Re =0(l/≪). These results are also compared with those from a full-scale explicit calculation. Finally, wave-growth rates are calculated from the Orr-Sommerfeld equation to show the stability to wave number with and without the electric field. The effect of the electric field is to lessen the range of the wave number in which the thin film flow remains stable.     

Two-component high-solid polyurethane coating systems based on soy polyols

Soybean oil based polyols—soybean oil phosphate ester polyols (SOPEPs)—having varying hydroxyl content and viscosity were prepared as low cost and low-VOC polyols for coatings applications. These SOPEPs were used as the hydroxyl component of “two-component polyurethane (2K-PU)” coating compositions and their film properties were studied. Blends of commercial polyester polyol and SOPEP in varying proportions were also used to formulate PU coatings. Their film properties were studied and compared. We found that SOPEP can be used as the sole hydroxyl component or as the reactive diluent for polyester polyols in 2K-PU coating systems. SOPEP, is derived from a relatively inexpensive and renewable resource and the use of SOPEP can substantially reduce VOC and cost of PU coating formulations. Presented at the International Waterborne, High-Solids, and Powder Coatings Symposium, New Orleans, LA, February 2002.     

AZ91D镁合金磷酸盐-高锰酸盐体系化学转化工艺

通过正交试验研究了以磷酸盐-高锰酸盐为基础的镁合金无铬转化工艺,讨论了工艺参数对转化膜厚度及其有机涂层耐蚀性的影响,并通过扫描电镜、能谱等方法分析了转化膜的微观形貌和化学成分。研究表明,当磷酸二氢铵为10～15g/L、高锰酸钾为5～10g/L时,磷酸盐-高锰酸的最佳处理工艺为:ZnSO43g/L,NaF3g/L,pH3,温度45°C。转化液pH对膜层厚度及有机涂层的耐蚀性有显著的影响。在试验参数范围内,转化膜的厚度及后续有机涂层的耐蚀性能随pH的减小而大幅度提高。经该工艺处理后,后续有机涂层的耐蚀性能提高10倍以上。     

Study on the crystal morphology and melting behavior of isothermally crystallized composites of short carbon fiber and poly(trimethylene terephthalate)

The spherulites of the short carbon fiber(SCF)/poly (trimethylene terephthalate) (PTT) composites formed in limited space at designed temperatures, and their melting behaviors were studied by the polarized optical microscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), respectively. The results suggest that SCF content, isothermal crystallization temperatures, and the film thicknesses influence the crystal morphology of the composites. The dimension of the spherulites is decreased with increasing SCF content, but whether banded or nonbanded spherulites will form in the composites is not dependent on SCF content. However, the crystal morphology of the composites depends strongly on the temperature. When the isothermal crystallization temperatures increase from 180°C to 230°C, the crystal morphology of SCF/PTT composites continuously changes in the following order: nonbanded → banded → nonbanded spherulites. Discontinuous circle lines form in the film when the film thickness increases from 30 to 60 μm. Basing on the SEM observation, it is found that these circle lines are cracks formed due to the constriction difference of the different parts of the spherulites. These cracks are formed when the film is cooled from the isothermal crystallization temperature to the room temperature at a slow cooling rate; while they will disappear gradually at different temperatures in the heating process. The crack will appear/disappear first around the center of the spherulite when the film was cooled/heated. The nontwisted or slightly twisted lamellas will reorganize to form highly twisted lamellas inducing apparent banded texture of the spherulites.