It is often assumed that raising the temperature of a system increases its wettability. The contact angles of hexadecane on a fluoropolymer were measured over a 130°C. temperature range. The advancing angle was found to be independent of temperature and the receding angles increased slightly with temperature. It is postulated that large temperature effects indicate specific interactions such as adsorption or desorption.
Usually a synthetic latex contains inorganic salts from the water-soluble initiator used in polymerization and from the impurities in the surfactant used to stabilize the latex. Upon removal of this electrolyte, by dialysis, the viscosity of the latex increases and becomes markedly shear thinning, i.e., non-Newtonian. When an electrolyte such as sodium chloride is added, the viscosity decreases immediately and may even become less than the viscosity of the original latex, and the flow behavior becomes Newtonian.
An apparatus used to study collision and coalescence of liquid aerosols and some of the physical quantities enhancing or hindering these processes is described. The relative trajectories, collision, and coalescence of two oppositely charged water droplets are shown for the droplets approaching at right angles. The droplets were 96 μ and 79 μ in radius and had velocities at impact of 330 cm./sec. and 110 cm./sec., respectively. It was found extremely difficult to make the two droplets collide when both were highly charged with the same sign of charge. However, droplets highly charged with the opposite sign of charge had a high collision rate.
Electrospray of Water and aqueous solutions is a simple, steady and continuous process for the production of charged droplets. Applications of this low cost spraying process, easy to scale up and environment friendly with low water consumption are first presented.This review addresses the Electro-Spray (ES) in the cone-jet mode, with focus on water ES with or without discharges in ambient air. The physical constraints to achieve steady water electrospray in ambient air are depicted to account for Electro-Hydro-Dynamic equilibrium required for the cone and jet formation on the one hand and to control electrical discharges in the gas around the liquid (with continuous corona or without any discharge) on the other hand. Operating conditions and empirical scaling laws between regulation parameters (liquid flow rate and corona current) and the properties of droplets such as the size and the charge are presented for the corona-assisted cone-jet mode of water electrospray in air. Subsequent working conditions to achieve the other steady water ES, without discharge, are then justified.The interest of this corona assisted cone-jet mode of electrospray in air for the steady production of self-dispersed unipolar water droplets (close to the Rayleigh limit) with unimodal size distribution is presented with one environmental application for filtration by bipolar-scrubbing of suspended particles from exhaust or ambient aerosols, with lab-scale efficiencies of High Efficiency Particulate Air filters.
Theories of the thermal force acting on aerosols are reviewed. Experimental measurements of the thermal force on spherical sodium chloride aerosols in argon are reported. The experimental measurements in the slip flow region are compared with slip flow theories, including a second-order theory presented here.
The deposition of aerosol particles from an air stream of velocity V0 upon a circular cylindrical fiber perpendicular to the stream in a homogeneous electrical field E0, has been investigated theoretically. The dielectric constant ϵc of the fiber controls by means of the parameter a = (ϵc − 1)(ϵc + 1) the additive inhomogeneous field of the fiber, which effectuates the deposition of the particles. When computing the trajectories, both inertia and image forces for charged particles have been neglected. The computations have been made for frictionless potential flow and for viscous flow according to Lamb.
A styrene copolymer with 2.3 mole % of methacrylic acid was modified by grafting short polycaprolactam side chains to the carboxyl residues. The creep and creep recovery was studied over a range of temperatures on graft polymers containing 20% dioctyl phthalate plasticizer. A sample in which the side chains contained on the average 5 caprolactam units was a rubber-like elastomer at 125°C., showing no evidence of an irreversible creep. This behavior was interpreted as due to the formation of a gel network by hydrogen-bonding between the polycaprolactam side chains. Covalent cross-linking could be excluded since the graft polymer was soluble in various solvent media. At higher temperatures the interpretation of the data was uncertain because of slow plasticizer loss and chemical degradation, but the molding behavior of the sample at 205°C. indicated that the gel structure had disappeared at that temperature.
Isotherms for the adsorption of nitrogen and argon on poly(methylmethacrylate) were obtained at three temperatures over a pressure range from a few microns to the saturated vapor pressure of the adsorbing gas. Differential and integral enthalpies and entropies were calculated and indicate a heterogeneous surface with adsorption energies higher than those observed for unsubstituted hydrocarbons. Clustering functions were calculated and indicate that the adsorption occurred in clusters throughout the range investigated.
The results of a light scattering study of four rubber latex samples using a dissymmetry technique are reported. Particle diameters found from the Rayleigh-Gans-Debye and Mie theories were in the range 1,400 to 2,000 A. In water the relative refractive index of these particles was m = 1.15 so that for particles of this size, the two accepted theoretical limitations for the RGD theory were exceeded. However, the results indicate that this theory can still be used to give particle sizes to within 5% for values of m approaching 1.15 and for diameters of up to 2,000 A.
In order to develop better semipermeable membranes for reverse osmosis, the mechanism of water transport must be determined. An evaluation of existing theories led to the hypothesis that degree of crosslinking and polar group content of a polymer were important factors in determining its semipermeability.
An apparatus is described for compressing and expanding insoluble monolayers, or films, present at an oil/water interface. Typical results for polymethylmethacrylate and pepsin monolayers at a petroleum ether/water interface are described.
Size and shape of micelles of Na and K salts of (tripentylmethyl)benzenesulfonic acid in n-heptane were determined from light scattering and sedimentation. These systems behave quite differently from most aqueous micellar systems, which entails special problems in the interpretation of the experimental results. The micelle size depends strongly upon soap concentration and temperature and upon the nature of the cation.
The surface characteristics of mono- and dioctadecylphosphoric acid spread at the air/water interface are presented. The influence of bulk pH, inorganic ions, and temperature were investigated. The values of the surface pK, calculated by the surface potential method, are also given.
A thermodynamic analysis of adsorption from a single-component fluid, either vapor or liquid, on the surface of a single-component solid is systematically developed. The analysis is based on the Gibbsian treatment of surface regions and assumes only that the interfaces are planar, that the solid and fluid phases are mutually insoluble, and that the solid is inert. The treatment is then applied to the interpretation of adhesional wetting (contact angle) and immersional wetting (heat of wetting) measurements. A relationship between the quantities obtained from these two types of wetting measurements is derived. This relationship is of the GibbsHelmholtz form and involves the dependence of the contact angle on temperature. Problems which arise in a proposed experimental test of the relationship are discussed.
Partition coefficients (KD = CH2O/Cisooctane) below the critical micelle concentration have been determined for a homogeneous and normal (Poisson) distribution series of p, t-octylphenoxyethoxyethanols (OPE1–10) in the system, isooctane-water, at 25°C. As the ethylene oxide (EO) chain length increases from 1 to 10, KD increases by four orders of magnitude. The calculated standard free energy change (ΔGEO0) of transport of 1 mole of ethylene oxide from the isooctane to the aqueous phase is −0.60 kcal. mole−1 for single species OPE's. Assuming a Poisson distribution of molecular weights and weak interactions between OPE molecules of varying EO chain length, one can calculate to a good approximation the partition coefficients of normal distribution OPE's from the partition coefficients of single species OPE's. Similarly, one can calculate the molecular weight distribution and average molecular weight of a given OPE in both the isooctane and aqueous phases as a function of the phase volume ratio of isooctane and water. An order of magnitude estimate of the partition coefficients of normal distribution and single species OPE's can be made from appropriate c.m.c. data. A 35°C. temperature increase decreases the partition coefficient of single species OPE9 by an order of magnitude. The corresponding standard enthalpy (ΔH°) and standard entropy (ΔS°) changes for the transfer of 1 mole of OPE9 from the isooctane phase to the aqueous phase are −12.9 kcal. mole−1 and −43 e.u., respectively. The partition coefficient of single species OPE9 increases with increasing concentration at concentrations in excess of the onset of micellization.
The absolute angular scattered intensities for a Mie scattering system have been determined. A Dow polystyrene latex of large diameter (DEM = 1.305 μ) was studied with unpolarized, vertically polarized, and horizontally polarized incident light. The necessary expressions relating the geometrical, optical, and calibration constants of a Brice-Phoenix photometer with the quantities directly related to the Mie intensity functions were developed. Two features of the experimental technique were explored in detail: the use of polarized incident radiation and the effect of the solid angle subtended by the receiver aperture. Generally, excellent agreement between the theoretical Mie intensity functions and the corresponding experimental absolute intensities was obtained over the whole angular range.
A new class of ion exchange membranes has been developed for possible use in conversion of brackish water to fresh water. These membranes are based primarily on inorganic ion exchangers and have small quantities of extremely stable high temperature resistant organic polymers as binders.
The interaction of nitrous oxide with real (oxide-coated) surfaces of both n- and p-type germanium has been investigated in the range of 10–300 torr and 200–400°C. The n-type samples promoted greater decomposition than the p-type samples. In all cases studied, not a trace of oxygen resulting from the decomposition could be detected in a mass spectrometer; obviously, the oxygen was incorporated in further oxide film formation. Pretreatment of germanium with oxygen decreased the extent of its interaction with nitrous oxide.
