ALBERT

Notes: Drag coefficients of aerodynamically smooth spheres varying in diameter from 0.0625 to 1.004 in. and in density from 0.195 to 7.80 g./cc. were obtained at acceleration rates ranging from 120 to -30 ft./sq.sec. The particles were subjected to relative turbulence intensities of 7 to 35% and to ratios of Eulerian macroscale to particle diameter of about 0.4 to 5.Quantitative measurement of particle drag coefficients was made possible by the use of a new particle tracing technique which permits the resolution of time to the nearest tenth of a millisecond. The resulting data extend farther into the supercritical flow regime than any other measurements previously reported.The variation in drag coefficient with Reynolds number indicates a continuous alteration in the flow pattern around a sphere in this region. The effect of turbulence is, essentially, to increase supercritical drag, although this effect was found to diminish with increasing Reynolds number. Possible mechanisms for the effects of Reynolds number and turbulence on the particle drag coefficient are suggested.

Notes: The breakup of a low speed horizontal jet is investigated. Weber's theory for the Newtonian jet is extended to a linear viscoelastic fluid. The theory predicts a dependence of breakup length on the elasticity number. Breakup lengths are measured for low concentration solutions of polyisobutylene in tetralin. Two molecular weights, several concentrations, and five capillary diameters were studied. A single correlation is obtained for all data which gives the breakup length as a function of the elasticity number, and the parameters of Weber's theory. At constant values of the Ohnesorge number and Weber number, the breakup length decreases with increasing elasticity number. The effect of the length of the capillary is studied. At large elasticity numbers short tubes give rise to slightly shorter breakup lengths than long tubes under identical flow conditions.

Notes: The hydrogenation of alpha-methylstyrene to cumene at 20 to 50°C. was studied experimentally with a trickle-bed reactor comprising a single vertical column of spherical porous palladium-on-alumina catalyst pellets. Other studies with powdered catalyst and studies in which catalyst pellets were swirled in a reactor allowed the intrinsic kinetics and effectiveness factor of the catalyst pellets to be determined. At 50°C. the reaction rate in the trickle-bed was about one-half of that in the absence of mass transfer limitations in the outside liquid film. The effectiveness factor of the pellets alone at 50°C. was 0.0057, and the tortuosity factor was 7.5. Experimental results are compared with four theoretical models for tricklebed reactors and criteria are presented for estimating whether mass transfer through the outside film is a significant resistance in an industrial trickle-bed reactor.

Notes: Entrance region and fully developed mass transfer from the inner core of annuli was investigated for a fully developed velocity profile and a Schmidt number of 760. Constant wall concentration was the satisfied boundary condition of the inner core.The ranges of parameters investigated were 21,400 to 75,600 for Reynolds number, 0.164 to 0.741 for the annulus diameter ratio, and 0.018 to 3.85 for the length to hydraulic diameter ratios.Experiments were performed in an open water flow loop. Mass transfer coefficients were obtained from weight loss measurements of benzoic acid life saver elements of various diameters and lengths. These elements were assembled as an integral part of the inner core of the annulus. Concentricity was maintained by a tensioning device.The local Sherwood number is found to be significantly affected by the annulus diameter ratio, Reynolds number, and the length to hydraulic diameter ratio. A correlation is developed which predicts 93% of the data used for its development to within ± 10%.

Notes: The onset of secondary motions between rotating concentric cylinders is related to the viscometric normal stress functions for a class of viscoelastic liquids which includes dilute polymer solutions. Both increased and decreased stability relative to a corresponding Newtonian liquid are possible for a given material, depending upon the particular relation between the viscometric functions and the geometric constants of the equipment. This predicted behavior is in agreement with experimental observations.

Notes: Analytic equations describing cyclic steady state diffusion in which the diffusivity depends on the direction of transfer, as well as on the system, have been obtained.By imposing the cyclic steady state constraint, of periodically repetitive concentration profiles, simultaneous solution of separate Fick's diffusion equations for the on-off segments of the cycle results in the desired equatins. The method of solution can be extended to more complex diffusion problems, such as coupled diffusion processes. Shallow bed experiments have been performed on particle-diffusion controlled, cyclic steady state ion exchange. Agreement between the predicted and experimental transfer was obtained. Variables and parameters affecting cyclic steady state diffusion are discussed.

Notes: Drag reduction data for five concentrations of a water-soluble polymer and three tube diameters are presented. The data are correlated by a single curve relating two dimensionless parameters; these have been obtained from a phenomenological analysis of the mechanism of drag reduction.

Notes: No Abstracts.

Notes: Gas absorption, pressure drop, liquid holdup, and loading behavior in a packed column have been investigated using packing materials almost geometrically identical but fabricated from three different materials (ceramics, Saran, and polyethylene). For the absorption of oxygen into sodium sulfite solution, observed values of the liquid-side, composite, overall mass transfer coefficient, KLa, were about 25% larger for the ceramic packing than for the polymeric packings. It was also observed that liquid loading occurs more readily in the case of the polymeric packing materials and it appears that the usual type of correlation is inadequate for predicting loading when polymeric packings are employed. In the case of liquid operating holdup no differences were observed from packing to packing. These observations are discussed in terms of the nature of the interaction between liquid and packing surface and it is pointed out how these phenomena may be fundamentally different from those of previous investigations, which relied upon surface-active agents added to the liquid.

Notes: A theoretical equation was developed to predict the enrichment produced by a single stage porous Vycor diffusion cell as a function of temperature. The separations of five binary gas mixtures were measured experimentally over a temperature range of 80 to 600°K. The agreement between theoretical predictions and experimental results was good over most of the temperature range. The largest deviations occurred when the operating temperature approached the critical temperatures of the gases. Mixtures of oxygen-carbon dioxide and helium-nitrogen were observed to become nonseparative at predicted temperatures. Overall, both separation and separative capacity were observed to increase with a decrease in temperature.

Notes: A model is presented to account for reduced mass transfer to drops falling through a continuous phase which contains a surface active agent. The fluid flow patterns are essentially laminar. The reduction in mass transfer is said to be due to a reduction in available interfacial transfer area and to changes in both velocity and pattern of internal circulation. These are shown to be functions of contact time and can be characterized. Experimental values agreed with the theoretically predicted ones with a deviation of less than 10%.

Notes: A theory has been developed for heat or mass transfer between phases which may have unsteady time dependent velocity fields. The configuration analyzed involves two concentric tubes, but the analysis can be extended to more than two phases, or streams, and to noncylindrical cross sections. For the configuration considered, the dispersion coefficient is found from first principles.It is noteworthy that the dispersion model given by Equation (15) or (63) and (64), which is consistent with the basic continuum model of Equations (8) and (9), is based on the superficial velocity rather than the interstitial velocity. This strongly suggests that experimental observations on packed beds, or other multiphase systems, should be interpreted on the basis of um, the superficial velocity, rather than the interstitial velocity which has been used often in the past.

Notes: No Abstracts.

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Notes: A general numerical-analysis procedure is presented for the screw extrusion of a non-Newtonian material. The full Navier-Stokes energy and continuity equations are used in the numerical procedure. The flow is taken as steady and incompressible, and the viscosity is written according to the Ostwald-de Waele model in which the viscosity is assumed to be inversely proportional to the square root of the second invariant of the rate of deformation tensor and exponentially dependent on the temperature.The procedure allows the prediction of vorticity, stream-function, swirl velocity, internal energy, and viscosity over any cross section of a groove containing plastic. Calculations for the mass extrusion rate and power consumption (shear rate) for the screw extruder are also given. Typical cases are considered for which all the quantities listed above are determined. The results compare favorably with other theoretical work.

Notes: No Abstracts.

Notes: The stability theory is used to predict jet length from jet inception to disruption for injection of one Newtonian liquid into a second immiscible Newtonian liquid. Knowledge of the length is essential for predicting the size of drops formed from jets. At low velocities jet length is controlled by the amplification of symmetrical waves which travel at the interfacial velocity of the jet. At higher velocities an abrupt lengthening of the jet may occur as a result of drop merging, and the jet length is then controlled by the growth rate of sinuous waves which are strongly velocity dependent. Jet disruption results from a geometrical limitation on the maximum amplitude of the sinuous waves. Predictions show good quantitative agreement with experimental data for thirteen mutually saturated systems over a wide range of variables and qualitative agreement with limited experimental data on the effects of initial disturbance level and mass transfer.

Notes: A method utilizing a diffusion controlled electrochemical reaction was used to measure average and instantaneous mass transfer coefficients at the solid-liquid interface in upward gasliquid climbing film flow in a vertical annular duct. These measurements give some indication of the mechanics of flow of the film, the extent of turbulence at the inner wall, and the effect of film thickness and wave motion on the mass transfer process at the inner wall. Predictions of incipient downflow of the film, shear stress at the inner wall, and interfacial shear stress were obtained from these measurements. Fluctuations in the velocity gradient at the inner wall were also studied. Results of this study are in good agreement with previous work and with theoretical predictions based on simplified momentum balance concepts.

Notes: The design of an experimental cocurrent spray dryer and its method of operation are described. The rationale for the development of some new measurement techniques and modifications to existing ones is discussed. These techniques were used to obtain profiles at several dryer levels of the air velocity, air humidity, and spray mass velocity for the case of a 30% sodium nitrate solution sprayed into 100°C. air. Somewhat less detailed measurements of the spray moisture and radial turbulent diffusivity were also made.The humidity and spray moisture measurements gave very nearly identical results for the progress of the evaporation along the length of the dryer. The axial injection of the spray was found to result in steep gradients for the air velocity, air humidity, and salt mass velocity but these were found to decay under the influence of turbulent mixing which is also generated by the spray injection.

Notes: A step-by-step prediction procedure has been developed to predict the evaporation of a sodium nitrate spray consisting of small drops moving at terminal velocity through the drying air. The procedure accounts both for the existence of radial gradients as well as radial mixing in the dryer and is selfsustaining except for values of the local air velocity.Because the procedure can be applied only to the free-fall zone, at some distance below the nozzle, a method was developed for the indirect determination of the amount of water remaining in the partly evaporated droplets at the beginning of the free-fall zone. This procedure was then applied to experimental data on drop size distributions obtained at the beginning of this zone. Owing to uncertainties concerning the salt concentration in the drops, a number of assumptions had to be made and the procedure was only partially successful in describing the spray evaporation, although it did compute the radial spray transfer. It was possible, however, to indicate by means of a model drop distribution the general validity of the procedure.

Notes: No Abstracts.

Notes: The mechanism by which oxygen is transported from capillaries into tissue for cell respiration has been a subject of interest since the work of August Krogh in 1919. Mathematical analyses of the diffusion process have been obtained by several investigators (11, 12, 18), but are limited in scope by the complicated nature of the problem. However, the solutions that exist give enough insight to inspire a more rigorous treatment. With the advant of electronic computers more complete analyses are now within reach (16).The human brain accounts for less than 4% of the total body weight, yet it uses 15 to 20% of the total body oxygen consumption. This high metabolic rate makes the brain particularly vulnerable to any change in the normal oxygen supply. The fact that following a cessation of cerebral blood flow, unconsciousness develops within 10 sec., and irreversible damage within 10 min., demonstrates the importance of understanding the dynamics of oxygen supply to the brain.

Notes: The use of heuristic structuring strategies in the development of computer programs for the synthesis of process designs is examined. By the employment of selection weights which are adjusted as experience is gained from past successes and failures, the computer is able to learn the sequence of structuring decisions which leads toward the optimal process design. The computer can develop competence in the synthesis of systems in a limited area of technology.

Notes: A generalized drying program that can simulate any drying conditions has been solved on a computer. The program includes the variation of humidity, temperature, and wind velocity over drying material. These three variables can be treated as functions of time. The correlations require knowledge of several basic properties of the material to be dried and were solved for the case of one directional heat and mass flow.The computer calculated results are checked with experimental data. The effective diffusivity and the solid surface resistance to mass transfer were evaluated by data obtained in three experiments.Solutions for constant drying conditions are presented in graphical form. Variations of such variables as humidity in a drier can be estimated from these curves but the computer program is more reliable.

Notes: A new throttling flow calorimeter has been incorporated into the recycle facility of the Thermal Properties Laboratory. Energy is added to the expanding gas while it flows through a stainless steel capillary tubing from an insulated resistance wire located inside the entire length of the capillary. The calorimeter is designed to operate at pressures up to 2,000 lb./sq.in.abs. in the temperature range from -240 to +250°F.Data on the isothermal effect of pressure on enthalpy for a mixture containing 5 mole % propane in methane are presented and compared with data from the literature.

Notes: The evaporation of n-decane into air from the surface of Celite particles, has been used for the establishment of mass transfer factors for both packed and fluidized bed systems. For these calculations log mean partial pressure differences were used. Actual concentration profiles of the transferable component were also experimentally measured by monitoring, at different bed heights, the concentration of n-decane vapor present in air used as the carrier gas. This was made possible through the use of an extremely sensitive hydrocarbon analyzer. The resulting profiles were used to obtain, by graphical integration, the actual driving force prevailing for each run. A nearly one-to-one correspondence was found to exist between the actual driving force and the corresponding log-mean value for both packed and fluidized bed runs.

Notes: Electrochemical techniques are developed to study the details of the flow around a single particle in a packed bed. Initial work has been done with a dumped bed of 1 in. spheres. Results are presented on the variation of the mass transfer coefficient and the shear stress around the surface of one of the spheres, the overall mass transfer rates to a sphere in a bed of inert spheres, and the effect of Reynolds number on the local mass transfer coefficient and the shear stress.

Notes: An improved free volume theory is presented, and is shown to predict the variation of viscosity with temperature and pressure satisfactorily for liquids composed of simple, nonpolar molecules, when the density is greater than twice the critical value. Allowance is made for the temperature dependence of the minimum free volume for a jump, and for the density dependence of the activation energy at constant volume. Corresponding states relationships are provided for these quantities, the reducing parameters being the temperature and molal volum at the melting point.

Notes: Calculations concerning the production of heavy water by the hydrogen sulfide dual-temperature exchange process require precise data on the physical properties of dry hydrogen sulfide and hydrogen sulfide-water mixtures for temperatures between 25 and 170°C., and for pressures between 200 and 340 lb./sq.in.abs. However, data on enthalpy of hydrogen sulfide-water mixtures were not found in the literature, and data published on hydrogen sulfide-water compositions at equilibrium were given at such large intervals of temperature and pressure that they could not be interpolated accurately enough by ordinary means. 1Specific volume and enthalpy of dry, superheated hydrogen sulfide vapor,2Composition of hydrogen sulfide-water vapor and liquid in equilibrium,3Enthalpy of hydrogen sulfide vapor saturated with water vapor,4Enthalpy of water liquid saturated with hydrogen sulfide vapor,5Deuterium distribution constants for vapor-liquid equilibrium.A study was undertaken to express the properties, listed below, with equations suitable for solution on a digital computer and useful in mathematical models of the process.New correlating constants were derived where needed. The equations and typical results are presented in this paper.

Notes: A perturbation series solution is derived for isothermal bubble dissolution and bubble growth from an initially finite size. The new solution is superior in several aspects to the quasi-stationary and quasi-steady state approximations derived previously. The accuracy and range of validity of the new results are investigated by comparison with finite-difference solutions of the equations governing bubble growth or dissolution. In addition, previous numerical solutions of the problem are compared to the finite-difference results of this study.

Notes: The steady, two-dimensional, incompressible laminar boundary-layer flow of power law fluids past a semi-infinite flat plate is studied analytically by the method of series expansion and the method of steepest descent (Meksyn's method). The shear stress of the fluids considered is proportional to the nth power of the velocity gradient. The solution obtained is a series of gamma function with the coefficient being a function of the material constant, n. The first ten terms of the series solution are then considered for the sum to determine the velocity gradient at the plate, fηη(0). The results obtained for fηη(0) and the coefficient of skin friction are in excellent agreement with the numerical solutions available in the range of 0.1 ≤ n ≤ 2.5.

Notes: An apparatus was constructed for making isochoric measurements of P-V-T properties. Experimental compressibility factors were obtained and are presented for methane, ethylene, and four intermediate mixtures at 60, 40, and 20°F., with pressures from 260 to 2,220 lb./sq.in.abs. Second and third virial coefficients and interaction virial coefficients were determined from the data. The compressibility factors and the virial coefficients are compared with the Benedict-Webb-Rubin equation of state, applied in its original form and in a recent generalized form.

Notes: The definition of filtration resistance is modified by considering relative solid-liquid velocity.The internal flow mechanism in a filter cake is reexamined in view of the movement of solids during compression. Under conditions of short filtrations involving highly concentrated slurries, the velocity of solids is shown to be comparable to the velocity of the liquid. A differential equation is proposed for the flow through compressible cakes in which the pressure gradient is assumed proportional to the difference in average velocities of the liquid and solid rather than to the average velocity of the liquid alone.An improved definition of the average filtration resistance is developed on the basis of the new flow equation.

Notes: A new theory for convection-free rinsing of flat plates was developed to include the drop dispersal mechanism as well as the previously considered diffusion mechanism. Cases where carryover is unequal to dragout were also included in the model. Based on film distribution data, the model offers better agreement with rinse data. The effect of drain time on film distribution and bottom drop volume was also investigated.

Notes: Equations are given that relate the entrance length to Reynolds number for pipe and channel geometries with a flat velocity profile as the initial condition. These equations are linear combinations of the creeping flow and boundary layer solutions. The former is obtained by minimization of the viscous dissipation using the finite element method. The equation for the pipe entrance is shown to be in good agreement with experimental data.

Notes: An expression is derived for the analysis of gas-phase mass transport in porous media in the presence of gradients in pressure and mole fraction. The behavior of porous media is contrasted with that of capillary tubes. A continuous-flow diffusion and permeation apparatus was employed for studies of mass transport in a fritted glass diaphragm. Measurements were obtained at varying levels of pressure and cover both isobaric binary diffusion and the permeation of pure gases and gas mixtures. These experimental results and previous data obtained by Hewitt and Sharratt and by Mason, et al. bear out the form of the equation and successfully provide independent checks of the three constants necessary to characterize a given porous medium.

Notes: Experimental values of the wave length and wave velocity have been obtained for dilute solutions of valeric and hexanoic acid for a vertical falling liquid film. The wave length was unaffected by the surfactants for Reynolds numbers in the range 5 to 100; however, the wave velocity was decreased for increased surface concentrations of the two acids. This is in direct contradiction to previous theoretical work, and the explanation for the anomaly is that the free surface velocity is greatly retarded by the adsorption of the surface active agents. In an effort to determine the extent of this retardation, an approximate form of the diffusion equation and the equations of motion were solved subject to boundary conditions describing the effect of the absorbed surfactant on the surface stress. The results indicate that the entrance length can be increased several orders of magnitude by the addition of small amounts of surfactant.

Notes: A study has been made of the mechanics of flow of low viscosity liquids through swirl spray nozzles. Discharge coefficients and spray angles have been measured for a series of nozzles designed to systematically determine dimensional effects not predicted by frictionless theory, in particular the effect of the ratios of swirl chamber diameter to orifice diameter and of orifice length to orifice diameter. It was found that a unique relationship exists between discharge coefficient and spray angle dependent only upon the value of the orifice length/diameter ratio. This result has been explained on the basis of an ideal flow theory extended to take into account the frictional decay of the vortex motion. A general expression has been derived which permits correlation of the flow characteristics of nozzles covering a wide range of designs.

Notes: The turbulent transport of mass, energy, and momentum was studied in a 4 in. diameter cylindrical column packed with 0.3 in. diameter stoneware spheres. Helium was used as a tracer material, with air as the mainstream fluid. The concentration of tracer present, the temperature, and the velocity of the gas were measured at several axial and radial increments. These data were analyzed numerically to obtain the radial component of the effective thermal conductivity and the radial component of the mass-dispersion coefficient as functions of radial position. Experimental conditions covered isothermal determinations at room temperature and nonisothermal determinations in which a temperature gradient was established in the radial direction. Significant differences were found between the isothermal and strongly nonisothermal results, primarily for the velocity profiles and thermal conductivities. Correlations were developed for the local values of the parameters.

Notes: The photodecomposition of acetone vapor was studied in a tubular flow, differential reactor at atmospheric pressure and from 82 to 112°C. The products included significant amounts of biacetyl along with carbon monoxide and ethane. A rate equation was developed from a sequence of elementary reactions believed to explain the photolysis of acetone. The effects of light intensity and acetone concentration, indicated in the derived rate equation, were confirmed by the data.The rate is less than first-order with respect to acetone, and this is believed to be due to reformation of stable acetone molecules by deactivation of CH3COCH3*.

Notes: Metal surfaces of titanium, aluminum, copper, lead, and zinc were irradiated by a 25 joules pulsed laser with an energy flux ranging from 106 to 108 cal./(sq.cm.) (sec.). The resulted cavities were sectioned, polished and measured to compare with the isotherms computed from several heat conduction models. Reasonable agreement was found between the experimental cavity diameters at the interface and those calculated from the disk source model. Also, a graphical correlation between the cavity depth and its interface diameter is presented.

Notes: A theoretical analysis of the operation of a Schildknecht type of column crystallizer is presented and simplified to three special cases. Experimental determinations were made of concentration profiles established during the purification of benzene with cyclohexane as impurity under steady state, batch conditions of operation. Benzene containing 34 to 500 ppm. cyclohexane was obtained by processing feed material with 5,000 to 30,000 ppm. cyclohexane. It was found that experimental data obtained under conditions of normal operation are well correlated by theoretical expressions if it is assumed that the crystals are not pure but contain cyclohexane at the level of 34 to 100 ppm. It was further established that the resistance to mass transfer between the liquid which adheres to the crystals and the wash liquid is negligible in comparison to backmixing effects as represented in the model by an eddy diffusion term. Smooth operation of the column was obtained at crystal rates below a limiting upper value and at oscillation frequencies above a lower limit.

Notes: In this paper the concept of a mass transfer section is applied to problems involving packed distillation columns and packed absorbers. When this concept is employed, the resulting equations required to describe packed distillation columns and packed absorbers are identical in form to those required to describe distillation columns and absorbers with plates. Data from the results of two field tests are presented and analyzed.

Notes: The Graetz-Nusselt problem for polymeric flow in a constant wall temperature tube was studied, using a temperature-dependent power law rheological model and temperature dependent fluid properties. Theoretical results compare within 6% of experimental results. The fluid model predicts an experimentally observed temperature maxima at a reduced radius between 0.7 and 0.8 for cooling at low flow rates.

Notes: No Abstracts.

Notes: No Abstracts.

Notes: An earlier study on interphase mass transfer in pulsating laminar flow has been extended to the case of a distensible tube. The physical situation studied corresponds to developed flow in a long tube with a traveling pressure wave of small amplitude impressed on the steady flow. The tube wall is free to expand radially. Asymptotic solutions are developed for large and small values of the frequency parameter. The interphase flux is much greater in distensible conduits than in the corresponding case in rigid conduits.

Notes: No Abstracts.

Notes: Experimental froth heights occurring on a perforated distillation tray were correlated with the determining system physical properties under distillation conditions. A photographic technique was used to measure accurately the foam and froth heights, produced in the 4 in. square test section of a laboratory distillation column, for several points in the composition range of five binary systems. Plate design parameters and operating vapor and liquid rates were held constant throughout the experimental study.The froth height results from this investigation (11), as well as those from studies (17) of a 6 in. distillation column, show a linear relation with the expression, UA2 ρv/(ρL  -  ρV), the frothing factor, for the ranges of the physical properties investigated.The foam height results of this study indicate that the mass transfer surface tension gradient, the heat transfer gradient, and the absolute value of surface tension all contribute to foam formation and stability. Because of the complex relation between the surface tension gradient and the frothing factor in relation to the degree of foaming, as well as the effects of other influencing variables, a unique correlation of the foam height data resulting from mass transture of the effect for several of the data points.This investigation was conducted to obtain experimental data which could provide a basis for correlation of the foam and froth heights occuring on an operating perforated distillation tray with system physical properties.

Notes: A theoretical analysis is presented for predicting the size of drops formed from a laminar cylindrical jet when one Newtonian liquid is injected through a nozzle into a second immiscible Newtonian liquid. The analysis couples stability theory with the requirement that the disturbances travel at the same velocity as the jet interface. Comparison of the theory with experimental data for thirteen mutually saturated liquid-liquid systems covering a wide range of physical properties shows a mean error of 11.7% in prediction of the specific surface.

Notes: The melt flow behavior of straight emulsion-polymerized PVC in a capillary extrusion rheometer has been found to depend upon both the molecular weight and the particle size of the sample. Observations of flow-rate, post-extrusion swell, and extrudate appearance, as functions of extrusion temperature and pressure, suggest that both molecular deformation and particle slippage are involved in the flow mechanism. The relative importance of these two modes of flow varies with extrusion conditions and with the PVC molecular weight and particle size. Particle slippage is favored by large particle size, high molecular weight, and low temperature and by a shear stress above a critical yield value. Apparent melt viscosity, swelling, and roughness are minimized under conditions corresponding to the maximum contribution of particle slippage. In the proper range of temperature and shear rate, straight emulsion PVC yields smooth, low-swell extrudates of excellent physical properties.

Notes: Re-examination of our work on internal plasticization of polyvinyl chloride leads us to suggest a number of guidelines in the synthesis of internally plasticized PVC with optimum combination of strength and low temperature properties: (1) use of comonomers of solubility parameter around 8.5 or 10.5, (2) use of a high molecular weight (long chain) comonomers in a low molar ratio, and (3) their non-uniform incorporation in the PVC chain.

Notes: A number of polymers have been “cold” extruded (i.e. at temperatures well below their normal melting temperatures) by the application of relatively high pressures. In all cases extrudates of relatively large cross-sectional area have been produced, and non-circular cross-sections have also been extruded. The extruded products has been evaluated and the results discussed. In general it has been found that whilst extrusion gives an oriented product, the increase in tensile modulus is much less than for a comparably drawn fibre. This phenomenon has been discussed in terms of the changes in crystalline structure produced by extrusion.

Notes: An analog computer-polymerizer system is described which polts continually the rate of polymerization in percent per hour and the total percent conversion. Computer components and their functions are briefly described and the polymerization vessel with its control instruments are shown. Methods of calibration and accuracy of the system are discussed.Polymerization rate curves for various initiators at various temperatures are presented. These curves show the typical autoacceleration of precipitating systems and the rate increase due to the gel effect. Experimental evidence is presented to explain the pressure drop seen in these curves at 70-75% conversion.

Notes: The influence of molecular weight and molecular weight distribution on the melt rheological behavior of two polystrenes of approximately the same weight average molecular weight, but of widely different molecular weight distribution, was determined. Then, using a series of capillaries with different length-to-diameter ratios in an Instron Capillary Rheometer, the entrance correction methods of E. B. Bagley and the relationships of W. Philippoff and F. H. Gaskins, the recoverable shear strain (SR) in the melt at the capillary wall for these mono- and polydisperse polystyrenes was determined. Shear modulus (G) and normal stress (PN) were calculated using the relationships: G = τRC/SR and PN = 2τRC SR, where τRC is the corrected shear stress at the capillary wall. These are compared to values obtained using a Weissenberg Rheogonimeter. These two polystyrenes were also injection molded into an ASTM specimen mold over a wide range of stock temperature, using a 12 OZ. in-line reciprocating screw injection press, and evaluated for mechanical property values. The effects of the elasticity parameters (SR G & PN) and their magnitude on the rheology, processability and mechanical properties of these polystyrenes are discussed.

Notes: Detailed crazing behavior in several plastic/rubber twophase polymer systems was studied by means of direct observation of ultrathin sections under the electron microscope by employing osmium tetroxide staining and hardening procedure. Samples used are ABS polymer, high -impact polystyrene and several PVC/rubber blends. All of the systems investigated showed evidence of stress -crazing when under flexural stress. Relationships between the dispersed rubber particles and the crazing behaviors were studied, and the role of rubber particles in the toughening mechanism of plastics was discussed based on these observations.

Notes: The effects of temperature and penetrant activity on the sorption kinetics and equilibria of a series of alkanes in glassy, biaxially oriented polystyrene were studied. Normal isomers of pentane, hexane, and heptane cause crazing of polystyrene film samples at high penetrant activities (〉 0.85). Crazing kinetics are identical to the kinetics of Case II transport. Transport of these normal hydrocarbons in glassy polystyrene in the temperature range 25 to 50°C is markedly non-Fickian; limiting Case II transport is observed at activities in exces of 0.6. Sorption appears to be controlled by highly activated relaxation processes including primary bond breakage at these high penetrant activities. Fickian diffusion behavior is approached, however, as penetrant activity is reduced. Sorption of the branched isomers of these compounds does not result in polymer microfailure. The sorption kinetics of the branched isomers, although time dependent, appear to be controlled primarily by thermally activated diffusion rather than large scale polymer relaxations which control Case II transport.

Notes: Attempts to use low-cycle fatigue techniques derived from the work of Coffin and Manson to predict the fatigue performance of six diverse structural plastics are discussed. Through an analysis of dynamic property and thermal behavior studies of polymer samples in reversed-tension fatigue, an improved model for the polymer fatigue process has been proposed. Laboratory test data are presented illustrating the relationship between the various models.

Notes: The viscosity of low-density crosslinked polyethylene was studied as a function of gel content and shear rate (3.75-33 sec-1). A simple model relating viscosity with gel content is suggested. It is shown that sol viscosity decreases with cross-linking propagation. The rheological parameters of the sol fraction are changed as a result, and it is natural that this effect should be utilized for flow calculations. Experimental data indicate a high degree of interaction between the sol molecules and the gel, and an experimental technique is presented for measuring it.The rheological parameters of crosslinked polyethylene are closely dependent on the gel content, viscosity and pseudoplasticity increasing with the latter.

Notes: Some of the thermodynamic and physical properties of crystals of linear polyethylene, formed from dilute solution are discussed. These properties include density, enthalpy of fusion, infrared absorption spectrum, selective oxidation and dynamic mechanical measurements. Despite the fact that electron microscopic examination reveals an apparent geometric regularity to these crystals, all these physical measurements yield a consistent interpretation in that they require about 15-20% of the chain units to be in a non-random conformation, and to form a disordered amorphous overlayer.Detailed studies of the experimentally observed relations between the crystallite thickness, crystallization temperature, and dissolution temperature (melting temperature in a dilute solution) are also presented. A thermodynamic analysis of the dissolution temperature-size relations, based on independently determined equilibrium solubility temperatures, indicates that the interfacial free-energy characteristic of the mature crystallites is significantly different from that involved in nucleation. The interfacial structures of the nucleus and the crystallites must, therefore, also be different. Size control by a nucleation process can be demonstrated from very general theoretical considerations. However, the detailed molecular structure characteristic of the nucleus cannot be specified solely from the fact that this process is size controlling.

Notes: Work at Stanford Research Institute on the deterioration of polymers is based on the assumption that aging in the light is the most serious problem and that it has at least three components that must be separated if we are to understand the overall process. We have started by measuring the production of free radicals on the polymer when pairs of t-butoxy radicals are generated from thermal decomposition of di-t-butylperoxy oxalate (DBPO) in bulk atactic polypropylene at temperatures approximating service conditions, 35-50°C. Our preliminary experiments have brought out experimental difficulties and have raised more theoretical questions than they have answered. Nevertheless, they show that the efficiency of production of polymer radicals is low and sensitive to the mobilities of the polymer chains. They also suggest that two kinetically different oxidation processes, with different dependencies on rates of initiation and with different susceptibilities to inhibitors, are proceeding simultaneously. The implications of these findings for results of some previous work and for design of improved accelerated tests is considered.

Notes: Starting with specific constitutive equations, methods of evaluating material properties from experimental data are outlined and then illustrated for some polymeric materials; these equations have been derived from thermodynamic principles, and are very similar to the Boltzmann superposition integral form of linear theory. The experimental basis for two equations under uniaxial loading and the influence of environmental factors on the properties are first examined. It is then shown that creep and recovery data can be conveiently used to evaluate properties in one equation, while two-step relaxation data serve the same purpose for the second equation. Methods of reducing data to accomplish this characterization and to determine the accuracy of the theory are illustrated using existing data on nitrocellulose film, fiber-reinforced phenolic resin, and polyisobutylene. Finally, a set of three-dimensional constitutive equations is proposed which is consistent with nonlinear behavior of some metals and plastics, and which enables all properties to be evaluated from uniaxial creep and recovery data.

Notes: The fatigue failure of thermoplastics and glass-reinforced thermoplastics is a function of cyclic stress or deflection level, test frequency, viscoelastic polymer parameters and matrix-to-fiber stress transfer. This paper reports an investigation of the modes of high frequency fatigue failure in glass-reinforced and unreinforced thermoplastics. In particular the effects and control of dissipative heating of a working specimen and the role of efficient matrix-to-fiber stress transfer are considered. A test procedure with which the severity of dissipative heating can be continuously followed and controlled during an accelerated fatigue test is described.

Notes: The flexural fatigue characteristics of boron fiber reinforced epoxy were shown to be strongly dependent on the aspect ratio of the reinforcing fibers. These composites were evaluated in a stiffness limited, constant maximum stress mode. The failure mechanism was found to be a combination of interfacial failure and brittle rupture of the matrix at 45 deg to the axis of the fibers. These fatigue cracks result in debonding of the outer fibers, thereby reducing the effective moment of inertia of the specimen.

Notes: Biaxial creep tests have been performed on thin-walled tubes of polymethyl methacrylate at 116°F and 50% R.H. The tubes were loaded radially up to a specified stress state, which was then maintained for a finite time. Additional tests involved a constant stress state for a period Δt1, after which the specimen was rapidly subjected to a second stress state which was maintained for a period Δt2. The experimental apparatus and procedure are described. The results for the range of stress, temperature, and time investigated show: 1) the creep behavior can be described by the form ∊ = ∊0 + mtn, where ∊ is the strain, ∊0 is the time-independent portion of the strain, and m and n are constants; 2) n appears to be independent of stress state in the fourth quadrant (-σz axial stress, +σθ tangential stress), and m is a linear function (log-log) of effective stress. In the first quadrant (+σz +σθ), the values of m and n are dependent on stress state, the constant m being also dependent on effective stress. Since two measurements are made for tangential strain ∊0, a description of the deformation can be obtained. Some results of pre-strain history and fracture are also presented.

Notes: Epoxy-Versamid specimens were loaded in tension up to failure at different constant strain-rates and temperatures. Results revealed three modes of behavior prevailing at different temperature-strain-rate regions and associated with brittle, ductile and rubbery failure modes. The ductile region was found to be confined within a narrow band on the temperature-strain-rate plane, and is characterized by a yield plateau in the stress-strain curve and by linear dependence of yield stress on log strain rate and temperature. Yield strain seems to be almost unaffected by strain-rate, but decreases slightly with temperature rise.Analysis indicated that experimental data within the ductile region are consistent with Eyring's formulation for non-Newtonian viscoplastic flows. It leads to the evaluation of the “apparent activation energy” and activation volume for the two epoxy systems tested.Comparison with previous work indicates that the above parameters as well as yield stress and elastic modulus tend to increase with the decrease of the Versamid content in the resin.

Notes: Neither the fringed-micelle, fringed-fibril or extreme folded-chain models explain the morphological and mechanical properties of highly drawn polyethylene. The modified folded-chain model, assuming that a substantial fraction (between 5 and 30 percent) of the molecules do not fold back at the crystal surface but go through the “amorphous” surface layer and enter the next crystal, avoids the insufficiencies of the above mentioned models.The elastic modulus and tensile strength of drawn polyethylene, both increasing with draw ratio, are to a large extent the consequence of the molecules bridging the quasi-amorphous layers and interconnecting the folded-chain lamellae oriented more-or-less perpendicular to the machine direction. The folds create enough space for the accommodation of more-or-less extended tie molecules in the quasi-amorphous layers between the lamellae. Electron microscopy and calorimetry of samples as drawn, annealed and/or etched with fuming nitric acid support the model.

Notes: Twelve polymers and copolymers reinforced with random short glass fibers are used for the study of the strength -composition relationship. Six of these reinforced systems are new and have not been reported elsewhere. The effect of fiber volume fraction on tensile and flexural strengths is related to the Kelly and Tyson equation. For each composition the strengthening factor, F, is calculated and discussed with respect to the structure of the polymer. One factor pertaining to the actual performance of fiber glass, fiber efficiency, K, has been extrapolated for the fiber glass used for this study. The effects of fibers on toughness and the Izod notched impact strength are discussed. It is the impact strength ratio and not the toughness which is used to describe the net result of reinforcement.The deviations between the wet and the dry strengths are used to illustrate the effect of the fiber -matrix interfacial bond. A new parameter, Δθ, is introduced to describe the effect of structure on the fiber -matrix interface. The effect of water at the fiber -matrix interface is further demonstrated through the determination of dielectric constant and dissipation factor of the composite before and after water immersion. The rule of mixtures was found to apply to dry electrical properties of composites.

Notes: The effects of shear stress on the crystallization kinetics and morphology of linear polyethylene and polybutene-1 were studied with the aid of a specially designed apparatus. With this equipment, it was possible to heat a thin polymer sample between glass slides to a melt temperature, quench the sample to a crystallization temperature, and then deform the sample in shear by applying a constant load to one of the glass slides. During the deformation, the crystallization process was observed and photographed under a polarizing microscope. Also, the displacement of the glass slide was simultaneously recorded which made possible a determination of the shear strain as a function of time.The results demonstrate that two phenomena may occur in the initially supercooled polymer samples in response to the applied shear stress. In one case, the sample deformed until it fractured, generally exhibiting no evidene of crystallization; in the other, the sample deformed until an inflection point was reached after which the sample became rigid. This latter phenomenon was attributed to crystallization.At low shear stresses, the inflection point was associated with the growth of spherulites which simply became large enough to bridge the glass slides and prevent further deformation of the sample. This generally occurred prior to the completion of the radial growth of the lamellae.At high shear stresses, however, no evidence of crystallization was seen in the microscope until the inflection point was reached. At this point, birefringence was observed in the sample. The resulting structure generally could not be resolved in the microscope, thereby indicating very profuse nucleation.The results obtained clearly demonstrate that the application of a sufficiently high shear stress to an initially supercooled melt has a substantial effect on the rates of crystallization of both polyethylene and polybutene-1. This was shown most dramatically at temperatures close to the melting point, e.g., both polyethylene at 130°C and polybutene-1 at 113°C, which require over 104 sec to crystallize under quiescent conditions, crystallized at approximately 0.05 seconds.The application of a shear stress to a polymer melt is envisaged as resulting in molecular orientation. In accord with the theories of Flory, and Krigbaum and Roe, the associated decrease in entropy of the melt may be considered to increase the supercooling. Under high stresses at which large increases in supercooling result, crystallization occurs more rapidy at the high temperatures and with polymers of lower molecular weight. At low shear stresses, the influence of temperature and molecular weight on the crystallization kinetics is essentially the same as that obseved under quiescent conditions.Observations through the microscope have shown that the application of a shear stress to a polymer melt leads to large increases in the number of crystalline structures formed and to the formation of oriented morphologies. This latter phenomenon arises due to nucleation lines formed by impurities and spherulites in the deforming melt. The impurities and spherulites apparently cause a disturbance which is thought to result in a local increase in stress of the melt and, hence, a local increase in supercooling. Lamellae then nucleate on these lines and grow out radially.

Notes: Empirical test data on low-density polyethylenes exposed to the elements for very long times are compared with results on samples of the same materials subjected to artificial “weathering” in a modified carbon arc machine.The test results conform to the expression \documentclass{article}\pagestyle{empty}\begin{document}$$ t_a = B + t_n^k $$\end{document} where ta is hours of accelerated weathering, tn years of natural exposure, and the constants B and k have values of 150 and 2.4, respectively, for the materials and test conditions involved.Earlier results are confirmed in that optimum weather resistance is found to depend on good dispersion of a fine-particle black. Protection improves with concentration up to the limit of about 5% by weight imposed by degenerative effects on mechanical properties from higher loadings of the fine channel blacks. Dependence of weatherability on molecular weight (melt index) is noted.

Notes: This discussion will illustrate some of the factors which go into the design of experiments required to solve problems in the field of plastics. Two quite diverse problems were considered. In the first case a series of experiments was described which provided a very general technique for predicting polyethylene flow behavior as a function of shear rate over a wide range of temperatures from a minimum of new data. In this case the experimentation concerned only the viscous aspect of flow and was not limited by the availability of special samples. In the second case it was desired to learn what the effect of a specific molecular structural variable was on the general melt rheological properties of polyethylene. This required the polymerization of special samples followed by detailed characterization by both solution property and melt rheological techniques.

Notes: Some properties of multilayered films are summarized in relation to the properties of the component materials. Polymers may be selected for co-extrusion into layered films to obtain various combinations of properties, such as barrier, stiffness, heat sealability, optics, and toughness. Properly chosen combinations of high and low modulus materials exhibit mutual interlayer reinforcement. Permeabilities of multilayer films can be calculated from layer geometry and individual component properties.

Notes: Spherulitic films of polybutene-1 have been stressed under biaxial tension. Direct microscopic observations indicate that the deformation is localized at the spherulite centers and at the intersections of boundaries in agreement with previous results obtained with linear polyethylene. The results demonstrate an increasing tendency for brittle failure with decreasing molecular weight. Effects of surfactants and solvents are also presented.