Molecular weight distribution of nonionic surfactants. III. Foam,wetting, detergency,emulsification and solubility properties of normal distribution and homogeneous p,t-octylphenoxyethoxyethanols

The effect of mol wt distribution on the foaming, wetting, detergency, emulsification and solubility properties of p,t-octylphenoxyethoxy-ethanols (OPE's) has been studied by comparing normal distribution and homogeneous compounds: Ross-Miles foam studies indicate that, although homogeneous OPE_7-10 are higher in initial foam height than normal distribution OPE_7-10, their foam stability is poorer. Hard surface and textile wetting were studied by contact angle determinations and the Draves' skein test, respectively. An exact correlation exists between hard surface wetting by solutions of OPE's of a Teflon surface and surface tension lowering. Normal distribution OPE's are, in general, better hard surface wetting agents than the corresponding homogeneous compounds. In textile wetting, normal distribution OPE_5-10 are approximately equivalent in performance and by implication are probably equivalent in wetting performance to the corresponding homogeneous compounds. Hard surface detergency studies show that normal distribution OPE's are generally slightly superior in detersive power to homogeneous OPE's at corresponding ethylene oxide chain lengths. OPE₁₀ is the best hard surface detergent of the OPE series, there being no distinguishable difference in performance between homogeneous and normal distribution OPE₁₀. Emulsification studies on the system, water-isooctane, show that only normal distribution OPE₅ is capable of forming stable o/w emulsions. Both homogeneous and normal distribution OPE₃ and OPE₄ form stable w/o (invert) emulsions. Solubility studies in isooctane and Ultrasene show that homogeneous OPE₄ is soluble at lower temp than the corresponding normal distribution compound. Studies of aqueous OPE solutions at temp above their cloud points show that solubility of both homogeneous and normal distribution materials is of the same order of magnitude as their critical micelle concn and that homogeneous OPE₄ is more soluble than normal distribution OPE₄.     

Local compositions and local surface area fractions: A theoretical discussion

The basic constraint for any valid expression for local composition, derived by McDermott and Ashton, is shown to be equivalent to the conservation equation used in Flemr's analysis. A similar constraint for local surface fractions is derived. The applicability of quasi-chemical expressions for local composition or local surface area fractions is extended to different existing (random) models of solutions. Chao's and Kehiaian's treatments appear as special cases. The statistical thermodynamic derivation of UNIQUAC is discussed in the framework of the generalized treatment. A method for solving the quasi-chemical equations for quaternary systems is described.     

Effect of surface heterogeneity on surface diffusion in microporous solids

An experimental investigation of the effect of surface energetic heterogeneity on surface diffusion using Vycor and Graphon and as gases ethane, propylene, nitrogen, and helium confirms published reports that surface diffusion proceeds more rapidly on the energetically homogeneous Graphon surfaces. Activation energies for diffusion are found to be about the same for Vycor and Graphon; thus, it is postulated that a major factor in the difference is surface roughness. A comparison of surface diffusion models shows that Fick's Law correlated results about as well as a hydrodynamic model. Both models fail to allow adequately for surface coverage. A comprehensive form of Fick's Law for surface diffusion is proposed.     

Using field theory to measure surface resistivity of high-resistance polymeric films

Theoretical expressions based on Ohm's law for field theory were derived to measure surface resistivity of high-resistance polymer films using parallel plate and concentric circular electrodes. Experimental measurements of resistivity were compared to experimental measurements using conventional expressions based on Ohm's law for circuit theory. Expressions based on Ohm's law for circuit theory were found to be inadequate for measuring surface resistivity. The surface resistivity of high-resistance films can be accurately measured if electric field theory is used to include the effects of electrode structure, if relative humidity (RH) and temperature are controlled, if the level of applied voltage is limited, and if the measuring system is shielded from extraneous electric and magnetic fields. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2856–2862, 2001     

On the use of Washburn's equation for contact angle determination

A systematic study on the possibility of Young's contact angle determination from Washburn's equation was performed using the so-called thin-layer wicking technique in which the rate of penetration of a liquid into the porous layer of a solid is measured. Commercial (Merck) SiO₂ deposited on the glass plate for thin-layer chromatography was used as a model solid and n-alkanes (from pentane to hexadecane), diiodomethane, and α-bromonaphthalene were employed as the probe liquids. It was shown that the contact angle calculated from Washburn's equation was not equal to Young's contact angle of a drop of the same liquid, placed on a flat surface of the solid. Consequently, the solid surface free energy components calculated using contact angles from Washburn's equation are not the true values. However, the approach previously suggested by us has been verified again, as it gives consistent values of the surface free energy components determined from all the liquids used.     

Threshold angle and valid fracture of the sectored flexural specimen

The sectored flexural specimen was developed over a decade ago to measure the strength of ceramic and glass tubes and cylinders in which flaws on a tube's or cylinder's outer surface are limiters of axial tensile failure stress. Using the specimen's geometry, the associated axial tensile failure stress can be analytically calculated from the failure force measured from simple uniaxial bending, and multiple specimens (and test data) can be harvested from a single tube or cylinder. The sector angles of specimens in previous studies were somewhat arbitrarily chosen and usually produced validly occurring fractures and data; however, if the angle used was too small (relative to the tube's or cylinder's geometry), then undesirable application-irrelevant edge-located failures resulted. To avoid such failures in specimen design, a threshold sector angle was identified to guide the selection of a minimum sector angle (and consequential cross section) for any arbitrary sector flexural specimen harvested from a tube or cylinder. If the sector angle of the specimen is larger than the threshold value, then fracture will not occur at a specimen's edge and the measured axial failure stress will be limited by surface-located flaws on the tube's or cylinder's outer surface.     

Investigation of Aerosol Surface Area Estimation from Number and Mass Concentration Measurements: Particle Density Effect

For nanoparticles with nonspherical morphologies, e.g., open agglomerates or fibrous particles, it is expected that the actual density of agglomerates may be significantly different from the bulk material density. It is further expected that using the material density may upset the relationship between surface area and mass when a method for estimating aerosol surface area from number and mass concentrations (referred to as “Maynard's estimation method”) is used. Therefore, it is necessary to quantitatively investigate how much the Maynard's estimation method depends on particle morphology and density. In this study, aerosol surface area estimated from number and mass concentration measurements was evaluated and compared with values from two reference methods: a method proposed by Lall and Friedlander for agglomerates and a mobility based method for compact nonspherical particles using well-defined polydisperse aerosols with known particle densities. Polydisperse silver aerosol particles were generated by an aerosol generation facility. Generated aerosols had a range of morphologies, count median diameters (CMD) between 25 and 50 nm, and geometric standard deviations (GSD) between 1.5 and 1.8. The surface area estimates from number and mass concentration measurements correlated well with the two reference values when gravimetric mass was used. The aerosol surface area estimates from the Maynard's estimation method were comparable to the reference method for all particle morphologies within the surface area ratios of 3.31 and 0.19 for assumed GSDs 1.5 and 1.8, respectively, when the bulk material density of silver was used. The difference between the Maynard's estimation method and surface area measured by the reference method for fractal-like agglomerates decreased from 79% to 23% when the measured effective particle density was used, while the difference for nearly spherical particles decreased from 30% to 24%. The results indicate that the use of particle density of agglomerates improves the accuracy of the Maynard's estimation method and that an effective density should be taken into account, when known, when estimating aerosol surface area of nonspherical aerosol such as open agglomerates and fibrous particles.     

Soil Clean Up by in-situ Aeration. I. Mathematical Modeling

Abstract

Mathematical models are developed suitable for use in evaluating the feasibility of in-situ vapor stripping approaches for selected chemicals and site-specific environments. These models simulate the operation of both laboratory soil stripping columns and field-scale vacuum extraction wells (vent pipes). The effect of an anisotropic Darcy's constant is examined and the compressibility of the extracting gas is taken into account. The models incorporate the assumption of local equilibrium for the volatile compounds between the condensed and vapor phases. These models may use Henry's law or more complex isotherms for this equilibrium. A method is developed for calculating Henry's constant from field analytical data, and it is noted that use of Henry's constants calculated from laboratory data on solutions of volatile solutes in pure water can lead to very serious errors. It is shown that evacuation wells should be screened only down near the impermeable layer beneath the zone of stripping (unsaturated zone) for most efficient functioning     

An analytical approach for the adhesion of a semi-infinite elastic body in contact with a sinusoidal rigid surface under zero external pressure

An analytical approach for the adhesion of a semi-infinite elastic body in contact with a sinusoidal rigid surface under zero external pressure is presented. Although Johnson (Int. J. Solids Struct. 32, 423 (1995)) has proposed an analytical solution for a slightly wavy surface, while Zilberman and Persson (Solid State Commun. 123, 173 (2002); J. Chem. Phys. 118, 6473 (2003)) have given a numerical solution for a highly wavy surface by considering the curvature of the contact area in the calculation of the interfacial term of the total energy, our solution is not only for small amplitude of roughness (i.e., the slightly wavy surface as Johnson's) but also for large amplitude of roughness (i.e., the highly wavy surface as of Zilberman and Persson). Our solution considers the curvature of the contact area as do Zilberman and Persson. Our results which are obtained for the total energy and equilibrium condition of the system agree with both Johnson's and Zilberman and Persson's results. The effects of the material constants and the surface roughness on the adhesion are clearly expressed and discussed.     

Sorption of dissolved organics from aqueous solution by polystyrene resins—I. Resin characterization and sorption equilibrium

The results of sorption equilibrium studies indicate that adsorption is only one of the three mechanisms involved in removing organics from aqueous solution by polystyrene resins. The other two mechanisms are associated with the resin's capability to incorporate organics into their polymer matrix while swelling. To describe the overall sorption behaviour, it is not sufficient to characterize the resin structure by estimating pore size distribution and internal surface area of the dry polymers. The amount of swelling in different organic solvents must also be evaluated as an important structural parameter of polystyrene resins. The role of the different mechanisms depends on both the resin structure and the physical and chemical properties of the solute. The solute's affinity for the polystyrene surface can be correlated with the solute's benzene-water partition coefficient. A heuristic model is presented which relates the sorption capacity to both the resin and solute properties.     

Curvature dependence of Henry's law constant and nonideality of gas equilibrium for curved vapor–liquid interfaces

Curved interfaces between coexisting vapor and liquid phases are ubiquitous in nature, and the question of whether the Henry's law is applicable for highly curved vapor/liquid interfaces remains unsolved. Using stable surface nanobubbles that have highly curved interfaces as examples, we investigate the viability of Henry's law with molecular simulations and thermodynamic analysis. We show that the prediction of Henry's law displays an increasingly deviation from the simulation results as nanobubble curvature increases. Such a curvature dependence of Henry's law constant is ascribed to the nonideality of gas in liquid phase because of the required gas supersaturation for stabilizing nanobubbles. Based on the effect, we develop a relationship for determining Henry's law constant from the level of gas supersaturation, as well as a robust relationship between gas supersaturation and nanobubble radius.     

Distribution of grafted poly(acrylic acid) in polyethylene film

The morphology of acrylic acid-grafted high-density polyethylene film and the distribution of poly(acrylic acid) in grafted film are examined. The grafting was carried out in the acrylic acid aqueous solution with or without Mohr's salt (an inhibitor of homopolymerization) by preirradiation method. It has become clear that without Mohr's salt the grafted poly(acrylic acid) layer is formed on the surface of the film, while in the presence of Mohr's salt the grafting layer consisting both of poly(acrylic acid) and polyethylene is formed on the inside of the surface.     

Electrophoresis of pH‐regulated particles in the presence of multiple ionic species

An electrophoresis model taking account of the pH‐regulated nature of particles and the presence of multiple ionic species is proposed for arbitrary surface potential and double‐layer thickness. It successfully simulated the electrophoretic behavior of Fe₃O₄ nanoparticles in an aqueous NaCl solution with pH adjusted by HCl and NaOH. The estimated zeta potential is compared with those from the conventional models, Smoluchowski's, Hückel's, and Henry's formulas. Due to the violation of the assumption of low and constant surface potential, these formulas yielded appreciable deviations (e.g., 23–30 mV at pH 9). With the surface charge density measured by titration and the zeta potential by electrophoresis, the true surface potential is estimated through a triple‐layer model. The estimated true potential is typically 1.5–10 times larger than the zeta potential, implying that using the latter in relevant calculations (e.g., stability and critical coagulation concentration) might yield appreciable deviation. © 2013 American Institute of Chemical Engineers AIChE J 60: 451–458, 2014     

Theoretical analysis of water diffusivity estimated by Crank's equation

Varied water diffusivities estimated by Crank's equation have been reported. However, the corresponding theoretical explanation is still not available. Here reported is our effort about this concern. A model combining the Fick's second law diffusion with a convective boundary condition on the material surface is solved numerically, and the obtained solution is used to estimate water diffusivity through Crank equation. The result shows that a significant underestimation of water diffusivity occurs due to a failure to account for appropriate boundary, which may imply that Crank's equation need be further improved.     

Surface Science and Catalysis—Studies on the Mechanism of Ammonia Synthesis: The P. H. Emmett Award Address

Abstract

About 5 years ago a Battelle Colloquium on “The Physical Basis of Heterogeneous Catalysis” was held in honor of Professor Emmett where he presented an introductory talk on ″Fifty Years of Progress in the Study of the Catalytic Synthesis of Ammonia″ [1], a field to which he had made significant contributions during this whole period. So why another report on this topic? Justification can perhaps partly be obtained by some of Professor Emmett's concluding remarks which were not completely decisive with respect to the mechanism of this reaction: 'The experimental work of the past 50 years leads to the conclusion that the rate-determining step in ammonia synthesis over iron catalysts is the chemisorption of nitrogen. The question as to whether the nitrogen species involved on the surface is molecular or atomic is still not conclusively resolved. In fact, our own work in this field was mainly induced by this paper, and continuing discussions and correspondence with Professor Emmett were extremely helpful during its progress. I am therefore very much honored to be this year's recipient of the Emmett Award.     

Effect of surface roughness on methane hydrate formation and its implications in nucleation design

As a new form of energy with substantial potential, natural gas hydrate will play a crucial strategic role in the future due to its vast reserves and broad industrial application prospects. To better comprehend the nucleation and growth mechanism of clathrate hydrate, an enhanced thermodynamic model was proposed based on the wall roughness model and nucleation theory. In general, we discovered that the nucleation of hydrate on a smooth wall surface conforms to the conclusion of classical nucleation theory. However, curvature and surface roughness are frequently characterized by hydrophilicity's inhibition of hydrate and hydrophobicity's enhancement. The specific situation is more complex and requires specific analysis and discussion. Nonetheless, this also explains the uneven distribution of hydrate nucleation induction time. Our research reveals a fundamental method for designing or manipulating the heterogeneous nucleation of hydrates. We foresee promising applications in hydrate-related technologies based on the fractal structure of the substrate's surface.     

Modifying a Stainless Steel for PEMFC Bipolar Plates via Electrochemical Nitridation

AISI446 stainless steel was electrochemically nitrided at room temperature. X‐ray photoelectron spectroscopy (XPS) analysis indicated that the nitrided steel was covered with surface ammonia and a layer of nitrides (mainly of mixed chromium nitrides). The nitride layer for 4 h nitrided steel at –0.9 V was about 2.5 nm thick. Dominating oxides appear on the steel's surface, so nitrogen incorporated oxides is a suitable term to describe the nitrided surface. The nitrided surface showed very low interfacial contact resistance (ICR) and excellent corrosion resistance in simulated polymer electrolyte membrane fuel cell (PEMFC) environments. The excellent stability of the nitride steel was confirmed by XPS depth profiling before and after testing in the PEMFC environments. Electrochemical nitridation provides an economic way for modifying the steel's surface to approach the U.S. Department of Energy 2015 goal for bipolar plates.     

Surface modification with acrylic polyampholytes 1, adsorption of acrylic polyampholytes on fiberglass reinforced plastics,and characterization of the polymer adsorbed surfaces

The adsorption of acrylic polyampholytes on fiberglass reinforced plastics (FRP) was investigated using random copolymers derived from (dimethylamino)ethyl methacrylate (DM), methacrylic acid, and t‐butyl methacrylate (t‐BMA). The effect of the copolymer structure changes on the adsorption and the interactions between the copolymers and the surface were assessed using ζ‐potential and contact angle measurements, NMR, and ESCA. The copolymer having the composition of 58 mol % pDM, 38 mol % pMMA, and 4 mol % pt‐BMA was adsorbed on the FRP surface at pH 7, and it formed the highest hydrophilic surface among the tested copolymers. An analysis by use of atomic force microscope revealed that the copolymer afforded a uniform 4–6 nm thick coverage on the FRP. We concluded that the interactions between the copolymer's cationic sites and the anionic FRP surface are important as well as the hydrophobic interaction for adsorption. Furthermore, it is suggested that the hydrophilicity of the copolymer's adsorbed surfaces is related to the density of the copolymer's anionic sites. These results indicate that the ampholytic structure of the polymers would be essential for the surface modification on the FRP. The effect of functional groups of surfaces on the acrylate adsorption was also assessed using surface plasmon resonance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4454–4461, 2006     

Surface tension and specific volume of copper–titanium melts measured by the sessile drop method

By using non-wetted and inert calcium fluoride substrates as plates or crucibles (cups), it is possible to extend the sessile drop method and its more precise version 'large drop' method for surface tension measurement of highly chemically active alloys. The surface tension and density of copper-titanium alloys over a wide range of titanium concentration (up to 70 at%) at temperatures between 1000 and 1250°C were measured. The surface tension-concentration dependence for Cu-Ti melts deviates positively from the Zhychovitsky theoretical isotherm for ideal solutions. The compression of alloys is observed. The copper-titanium melts deviate negatively from Raoult's law. The work of adhesion of Cu-Ti melts to CaF₂ was also determined and it was found to be 820 ± 65 mJ/m² for Cu + 70 at% Ti.     

Cationic latex interaction with pulp fibers. II. Modification of sheet properties by styrene butadiene latex with quaternized amino groups

Unbeaten kraft fibers covered with experimental cationic latexes were formed into sheets in which direct fiber-fiber bonds are replaced by polymeric bonds. The effect on sheet properties—breaking length, elongation at break, folding endurance, opacity, and light scattering—was evaluated as a function of latex composition. The composition was altered by either the ratios of styrene to butadiene in the polymer or by mixing soft film-forming and hard nonfilming latex. It is shown that, regardless of latex composition and mechanical properties of the polymeric film, all the latexes can modify the sheet properties to a similar extent, providing that the sheets are heated above the polymer's glass transition temperature. An improvement of tensile strength is accompanied by increased elongation. As a probable mechanism of reinforcement, it is suggested that the polymer acts as a filler of the fiber's surface irregularities, thus providing a larger contact area between fibers and an improved stress transfer between them.