Viscous State Research Articles

The mechanical and electrical properties of earth's asthenosphere

An adequate theory of continental drift can be based on heat transfer theory, but it does demand the acceptance of a large downward revision of traditional estimates of average upper mantle temperatures and a consistent understanding of lithosphere and asthenosphere in terms of a difference in rheological behaviour under prolonged non-hydrostatic stress. The recognition that an extremely viscous average state of the upper mantle is self regulating both requires and permits an explanation of magma generation at a strictly limited rate (when averaged for the whole planet over a few years) in terms of unsteady and local deformational heating. The activity of water as a reducer of silicate creep resistance is used to develop the hypothesis that water produced by an amphibole dehydration has been effectively trapped in the Earth and is the underlying cause of a low seismic Q ∼ 50 and an electrical conductivity 10 −2 −10 −1 ohm −1 m −1, at depths of ∼ 100 km. At the predicted low horizontally-avera temperatures, the conductivity contrast of rock and aqueous solutions is very large, and mantle electrical conductivity studies now look best-suited to explore this trapping process, and the distinctly recognisable possibility that the uptake of ocean water in the subduction process exceeds the rate of loss that can be explained purely through magmatic activity.

Controlled slow release of chemotherapeutic drugs for cancer from matrices prepared by radiation polymerization at low temperatures.

The vinyl polymer-chemotherapeutic agent composites of various shapes (rod, tablet, membrane, microsphere, and powder) were prepared by radiation polymerization at low temperatures for the purpose of durable controlled slow release of drugs from implanted matrices. Bleomycin hydrochloric acid, mitomycin C, and 5-fluorouracil were tested as chemotherapeutic drugs entrapped in poly(diethylene glycol dimethacrylate) including a small quantity of a polymer such as poly(styrene), poly(vinyl formal), poly(vinyl acetate), poly(methyl methacrylate) on polyethylene glycol No. 600. The release rates from the matrices depended much on the kind of polymer, drug, and monomer concentration in polymerization and also on the shape of the composite. The release of these drugs from polymer matrices obeyed the diffusion-controlled release mechanism based on Higuchi's equation and was durable for more than thirty days. It was found that the release rate can be controlled easily by design of the shapes and structures of the polymer matrices.

Static and dynamic Kerr-effect studies of glycerol in its highly viscous state

Static and dynamic Kerr-effect studies have been made for glycerol in the range 205–255 K. The static measurements indicate extensive association of the molecules and that this increases with decreasing temperature, in accord with the results of dielectric studies. The dynamic Kerr effect shows one, near single-relaxation time, process at all temperatures with the rise and decay correlation times being related according to τK,r=(1.45 ± 0.20)τK,d. Dielectric relaxation measurements made concurrently with the Kerr-effect relaxation measurements show that τD≈(½)τK,d. The relationships between the relaxation of the Kerr effect, dielectric ultrasonic and dynamic light-scattering processes are discussed in terms of the structural relaxation mechanism and cross-correlation functions which appear for each technique. The Kerr-effect relaxation is slower than that for dielectric relaxation at a given temperature which is, in turn, slower than that for the light-scattering relaxation. The importance of mixed Rayleigh and Mountain relaxation for the latter is discussed in relation to the theory of Demoulin and co-workers.

The mechanical properties of gels in dimethyl phthalate of cellulose acetate of different degrees of substitution

The dependence of the temperature of transition to the high elastic and viscous flow state, on the degree of substitution and molecular weight of cellulose acetate has been found, using thermomechanical and dynamic mechanical methods. The molecular weight of the mechanical segment of the polymer was found from the temperature range of the high elastic state. The relaxational transitions in cellulose acetate gels in dimethyl phthalate are classified as segmental or local types, in accordance with the calculated apparent energies of activation and the lengths of the segments between branch points. Increase in the degree of substitution and in the concentration of the polymer raises the transition temperatures and increases the dynamic modulus and the apparent energy of activation for the relaxational processes in these systems.

Electro-convection in a dielectric liquid layer subjected to unipolar injection

The problem of electric charge convection in a dielectric liquid layer of high ionic purity, when subjected to unipolar injection, is in many ways analogous to that of thermal convection in a horizontal fluid layer heated from below, although no formal analogy can be established. The problem treated is intrinsically more nonlinear than the thermal problem. We consider two asymptotic states of convection: one where the whole motion is dominated by viscosity, and one where inertial effects dominate. In each state, two or three spatial regions are distinguished. From the approximate equations that hold in the different regions, information about the variation of the different quantities with distance from the injector is obtained, and further approximations permit us to establish the dependence of the current density ratioI/I0(called theelectric Nusselt number) on the stability parameterT=M2R= εϕ0/Kρν, and on 1/R= ν/Kϕ0, which is an equivalent Prandtl number (ε is the permittivity, ρ the fluid density,Kthe mobility, ν the kinematic viscosity, and ϕ0the applied voltage). In the viscous state, the analysis givesI/I0∞T½; in the inertial state the lawI/I0∞ (T/R)1/4=M½is obtained. SinceMis independent of the applied voltage, the latter law shows the saturation in the electric Nusselt number observed in earlier experiments. The transition in the states is associated with a transition number (MR)T[gap ] 30, which is an electric Reynolds number, related to an ordinary Reynolds number of about 10.The experimental results, obtained in liquids of very different viscosities and dielectric constants, verify these theoretical predictions; further, they yield more precise numerical coefficients. As for the transition criteria, the experiments confirm that the viscous and inertial effects are of the same order whenRe[gap ] 10. It was also possible to determine roughly the limits of the viscous and inertial states. The viscous analysis remains valid up to a Reynolds number of about 1; the inertial state can be considered valid down to a Reynolds number of 60. Schlieren observations show that the motion has the structure of very stable hexagonal cells at applied voltages just above the critical voltage, which are transformed into unstable filaments when the voltage is increased further. At even higher voltages, the motion finally breaks down into turbulence. It may be of interest to point out that, whenM< 3, the electric Nusselt number approaches 1, which is equivalent to the situation in thermal convection at low Prandtl numbers.

Re: Contact Theory of Adhesion

Abstract Recently we have developed a contact theory of adhesion published under the title “Interfacial Contact and Bonding in Autohesion”.1 The theory was formed for the case of polymers in a highly viscous state, where it is hard to bring them together for bonding. For low viscosity materials coalescence occurs very rapidly and contact is not a problem. However, most cases of adhesion that give us problems belong to the former case where establishment of contact between the two surfaces is the primary requirement. The rate of contact formation is controlled by the shape of the surfaces in contact, the viscous or viscoelastic properties of the material comprising them and the contact pressure. This is handled by extending Hertz' contact theory2 by applying Alfrey's and Gurnee's elastic-viscous-viscoelastic analogy. Where-ever contact is established the interfacial bond strength may be obtained from molecular primary or secondary bond forces. This was obtained by using Good's4 6–12 Lennard-Jones potential...

A Surface Viscosimeter Based on Oscillations of Large Amplitude

This paper describes a very large amplitude torsional device for measuring surface viscosity. Its main feature is the possibility of submitting the floating ring to angles of oscillation as great as 270°, thus allowing study of the same film for the entire range of the elastic and the Newtonian viscous state. The design and performance of the viscosimeter is described, and certain possibilities for future investigations are briefly outlined.

Most important features of pre-stationary deformation regimes and stress relaxation of polymers in the viscous state

In the prestationary deformation regime relaxation times decrease both before and after passage through the ultimate shear strength, i. e., independent of whether the stresses at which relaxation began were growing or decreasing.

High elastic deformation of polymers in the viscous state

High elastic deformation of polymers in the viscous state

The glass transition temperature of filled polymers and its effect on their physical properties

AbstractThe glass transition temperature, dynamic shear moduli, and bulk viscosities of Phenoxy PKHH (a thermoplastic polymer made from bisphenol‐A and epichlorohydrin) filled with glass beads and Attapulgite clay were investigated. The glass temperature of the polymer increased with increasing filler concentration and with increasing specific surface area of the filler. The data were interpreted by assuming that interactions between filler particles and the polymer matrix reduce molecular mobility and flexibility of the polymer chains in the vicinity of the interfaces. From the measured moduli and the viscosities of the filled and unfilled materials, the modulus reinforcement ratio in the glassy state and the relative viscosity in the viscous state were obtained as functions of the filler type and concentration. The relative modulus for the glass bead composite system follows the Kerner equation, while the clay‐filled systems exhibit slightly greater reinforcement. The relative viscosities are strongly temperature dependent and do not follow conventional viscosity predictions for suspensions. It is suggested that the filler has a twofold effect on the viscosity of the composite materials; one is due to its mechanical presence and the other is due to modifications of part of the polymer matrix caused by interaction. Using the WLF equation to express all modifications of the matrix, one can isolate a purely mechanical contribution to the viscosity reinforcement. This mechanical part is approximately bounded by the theoretical predictions of Kerner,32 Mooney, 36 and Brodnyan,41 for suspension viscosities.

Natural convection in the molten core of a killed steel ingot

As we have shown earlier [1-3], the molten steel in the core of an ingot is intensely agitated for a very long t ime while it is hardening (for a 7 mg killed steel ingot the convection.t ime is 80 rain). As the killed steel hardens, the layers of liquid meta l at the crystallization front descend; here, in the lower portion of the still molten core of the ingot there is a gradual accumulat ion of stationary mel t and the boundary between the convective meta l and the stationary metal moves upward with t ime. We can list some causes responsible for the observed mixing of the mel t while the ingot is hardening 1) Agitation of the mel t as a result of the mechanica l effect of a jet of meta l during pouring. However, calculation shows that it is not possible to explain the very long convection t ime by the effect of a meta l jet during pouring. 2) Agitation of the mel t as a result of natural heat convection. Here the meta l is molten because it is above the liquidus temperature and the colder layers at the crystallization front descend, forcing the lighter me ta l at the center of the ingot upward [% 5]. Clearly, when heat is removed, natural convection must cease. According to Ivantsov [6] and the exper imental data of Tageev and Gulyaev [7] it takes 10 rain for the excess heat to be removed from the center of an ingot weighing 7 nag so that it is quite impossible to explain the very long ingot convection t ime in terms of this factor. 3) Some researchers [8] assume that the basic principle responsible for convection in a hardening ingot is the shrinkage of the meta l during hardening. To verify this hypothesis a bismuth ingot weighing 13 kg was cast in a steel cylindrical mold. After the ingot was cast, the radioactive isotope thal l ium-204 was added to the mirror. As is clear from the autoradiogtams obtained from this ingot (Fig. 1~ the thal l ium isotope, being entrained by the convective flow, penetrates deeply into the ingot although nothing can be said about shrinkage, in this case, the metal at the side crystallization front ascends. One exception is bismuth, which expands rather than shrinks during hardening 4. Agitation of the mel t as a result of the appearance of concentrated impurity streams during the process which, naturally, can ex plain the observed descending meta l current. 5. Melt convection as a result of the formation of a nucleating solid phase at the crystallization front and the subsequent descent of the enriched me l t along the crystallization front. We shall calculate the change in the volume of the circulating mel t with t ime for a prismatic killed ingot, assuming that in addition to heating the steel above the liquidus line convection is also caused by the presence of solid-phase particles in the boundary layer. To do this the entire hardening period is divided into two stages. In the first stage of the process when overheating is still present, the mel t current descends along the crystallization front because of natural convection. Here flow and heat exchange are turbulent. After e l iminat ion of overheating, thexe is a descending flow of meta l along the crystallization front in the second stage of the process; this is due to the enr ichment of the boundary with solid-phase nuclei . Metal flow in this stage is laminar . The mel t enriched by solid-phase nuclei accumulates in t he lower portion of the ingot; when the concentration of the solid phase passes the meta l creep boundary, mixing in this region of the ingot ceases. On the basis of the data of Nekhenedzi [9] and Khvorinov [10] we can assume that tile steel is still capable of flowing in the viscous state when up to about 20% of the solid phase is present. The thermal balance equation for the second stage of the process can be written as "~ 0 Scrdz = --(5~.'4f'cO)'{dVcr. (1)

Studies of viscosity as the probable factor involved in the improvement of certain barleys for chickens by enzyme supplementation

Synopsis The hypothesis that the sticky droppings and the poor performance of chicks fed on low‐enzyme barleys are due to hemicelluloses and related substances in barley, which in solution in the alimentary tract give rise to a highly viscous state, was tested. It is demonstrated that pectin significantly reduced chick performance and the droppings produced were very sticky. A pectin‐degrading enzyme quickly reduced the viscosity of a solution of pectin and significantly improved the performance of chicks. The effect of feeding a bacterial enzyme preparation on the viscosity of water extracts of the contents of the small intestines of chickens that were fed on a low‐enzyme barley, was studied. It is shown that the viscosities were reduced by the “enzyme”. The viscosities of extracts from chickens that were fed on barley alone were lowered by enzyme preparations that were effective in increasing the performance of chickens. Aqueous extracts of Australian barleys, steamed Irish barley and processed Irish barley were highly viscous, whereas similar extracts of raw Irish barleys had very low viscosities. The viscosities of the former barley extracts were markedly lowered by adding “effective” (i.e. those which improve chick performance) enzyme preparations to them. The “enzymes” gave similar results with a solution of β‐glucan, and it is concluded that the enzyme responsible for lowering the viscosities was endo‐β‐glucanase. A simple method for the determination of endo‐β‐glucanase activity is described. The activities of Irish barleys were high, but the activities of Australian barleys were very low. The enzyme was present in “effective” crude enzyme preparations. It is concluded that the poor nutritional value of low‐enzyme barleys is related to the glucan and β‐glucan components of barley. Under the particular conditions the glucan/β‐glucan components give rise to fairly stable highly viscous conditions in the small intestine.

Viscous Flow and Flow Temperature of Polymers

Abstract In recent years, E. V. Kuvshinskii and colleagues have published a series of articles devoted to thermomechanical studies of polymers. Some of these, together with some interesting data, led to strange conclusions concerning the absence of flow in polyisobutylene, polystyrene, and polymethylmethacrylate in thermomechanical experiments and also to the uselessness of distinguishing between the viscous flow state development and determination of flow temperatures of polymers. Obviously feeling a weakness in their argument, the authors of these articles showed, at the same time, that their results “do not refute the possibility of using the data from thermomechanical studies for technological purposes, including the establishment of proper temperatures for processing polymeric materials” (Ref. 1, p. 1704). We have established the fact that the position taken by E. V. Kuvshinskii and associates, in which they deny the existence of the viscous flow state of polymers and characterize flow temperatures, is in sharp contradiction to the current thinking concerning mechanical properties and structure of polymers. Their position adds nothing to our knowledge of the properties of polymers. Furthermore, their position is dangerous, because it docs not contribute to the clarification of the various phenomena taking place during the flow of polymers. This leads to confusion.

The Viscometric Properties of Polyesters. I. A Comparison between Crystalline and Amorphous Polyesters

Abstract From the study of the viscosity of aliphatic long-chain polyesters over a wide range of temperatures, the following results have been obtained : (1) Among aliphatic long-chain polyesters with ether bonds in the main chains, several crystalline polyesters have been obtained. (2) Accordingly, it has been possible to compare the temperature dependence of the viscosity of the amorphous and the crystalline polyesters with similar chemical structures. (3) When the temperature is raised, every apparent activation energy for viscous flow (E\eweq) approaches a fixed value, independently of the chemical structure of the polyester. (4) However, the viscous flow state of the amorphous polyester changes discontinuously in connection with the chemical structure near the melting point of the corresponding crystalline polyester. (5) In the “transition area” for viscous flow, the viscosity and the apparent activation energy (E\eweq) are, respectively, about 10 poises and 11 kcal./mol.

Structural Studies in the Western Part of the Skellefte District, Northern Sweden

Abstract Structural studies in the W part of the Skellefte district have given some new facts about the orogenic movements in this area. There are at least two generations of cleavage in the Kristineberg area caused by stresses perpendicular to them. The direction of stress has turned through 30° in a clockwise direction between the two folding stages. A third stage of deformation connected with the Revsund granite and with a stress almost at right angles to the stresses of the former stages is probable but signs of it are rarer. Dragfolds at the contacts of the Rudtjebacken ore show that the ore was intruded in a highly viscous state moving towards SE in relation to the wall rocks above and below. The ore emanations were evidently dewatered and concentrated during their ascent upwards in the dome. At the time of emplacement the ore was a mixture of sulphide crystals and a hydrothermal solution which acted as a lubricant. Drag-folds on the flanks of the dome indicate that it formed by cross folding. The a...

Infrared Emission Spectra of Quartz*

Infrared emission spectra of quartz have been recorded and analyzed. The spectra were taken every 0.2 sec on the materials heated under ablating conditions in an arc wind tunnel. Surface temperatures near 2400°K are deduced and emissivity values for the corresponding highly viscous state are estimated. The enhancement of the emissivity at wavelengths below 4.5 μ by the use of “white” quartz is reported. Details of the scanning spectrometer (sweep rate 3.5 μ/0.2 sec) and application to measurement of surface temperatures are presented.

A method for determination of maximum heat resistance of plastics

AbstractA new method for measuring heat stability and temperature of degradation of thermosetting plastics is described, as well as an improved method for the determination of transition temperature into glassy or viscous state for thermosetting resins. Magnitude of elastic deformation is tied in with length of polymer chain and lattice density.

Bond Strength of Tread and Breaker Stocks under Repeated Deformations

Abstract As the tire industry changed over to production from synthetic rubber a new form of service failure was encountered—stripping of the tread from the breaker. This phenomenon is most noticeable where SBR rubbers are used, and also at the boundary layer of pliedup rubbers differing in composition, having different moduli and different degree of cure in the zone of contact with each other. In recent times there have been carried out a considerable number of investigations of the dynamic strength of a system of pliedup rubbers. The results show that an important influence is exerted upon the bond strength of pliedup rubbers by their flow, which governs the increase in contact area in the boundary layers, by the diffusion of the separate links of the chain molecules of one pliedup layer into the other by the degree of the pliedup rubbers, and the bonding layers between the layers of rubber. The compounding ingredients also affect the bond strength. As a result a number of technological measures were taken to increase bond strength between the components of tires on the adoption of SBR in the industry. These were directed towards increasing the surface contact between the layers, and towards improving the surface of the semifinished products before plyingup. An important effect upon the improvement of the surface properties of tires was evidenced by increased pressure in the building process, roughening of the tread and breaker, pressing of the uncured casings after building, and introducing into tire formulas accelerator groups which ensure increase in the time spent by the stocks in the viscous flow state in the initial period of vulcanization. One method of attaining higher dynamic strength in the tread-breaker system was some increase in the modulus of the breaker rubber by increaisng the amount of channel black. A recently developed formula for tread rubber with increased elasticity and for a stiff breaker noticeably reduced the failures of tires from stripping of the tread from the breaker. Nevertheless this problem still occupies the center of attention in the industry.

Effect of Enzymes on Mechanical Properties of Tissues

WHILE investigating the effect of extending forces on the excised uterine cervix of the rat1 we found that at the end of pregnancy the tissue showed prolonged extension at constant rate under low loads, behaving as if the collagenous framework in it was not continuous, as it is in the majority of tissues, but was one in which the ultimate links were viscous. In the course of investigating this viscous state we tried the effect of soaking the tissue in solutions containing trypsin. This was found to increase dramatically the rate of extension under constant load. Similar results were obtained from rings of skin cut from around the body-wall of newly born rats. Chymotrypsin was also tried on these and found to have the same effect as trypsin.

鋼の燒入殘留應力に及ぼず變態及び熱收縮の影響

Using cylindrical Ni-Fe älloy, specimens, we measured the residual stress of quenching by G. Sachs' method, and studied the mechanism of the growth-of quenching stress by changing the method of the heat treatment and the alloy elements.By this study, we found the fact that, in comparatively low nickel alloy (16% Ni), when quenching tempsrature rises higher than thansformation point, it takes the thermal stress type (Outsidecompression, inside-tension), and when quenching temperature approaches immediately above the transformation point, it takes the transformation stress type (outside-tension, inside-compression). In high Ni alloy (26% Ni), however, no matter how the quenching temperature may be, the stress distribution takes the type of transformation stress, and its value is little, too. As we (authors) thought the cause of the latter depends on "the transformation plasticity" as reported by G. Wasserman and E. Scheil, we made a simple experiment and could assure it to be true. In other words, in the case of low Ni alloy (16% Ni), transformation takes place it the viscous state of high temperature and the stress changes into non-elastic strain when it passes the range of transformation, so it is not affected by "the transformation plasticity". On the contrary, we may conclude that in the case of high Ni alloy, the transformation takes place in the elastic state in low temperature, so it reduces the stress by "the transformation plasticity".