Showing papers on "Rheometer published in 1974"
TL;DR: In this article, an experimental study was carried out to investigate the viscoelastic behavior of calcium carbonate-filled polypropylene melts, using the Han slit rheometer.
Abstract: An experimental study was carried out to investigate the viscoelastic behavior of calcium carbonate-filled polypropylene melts, using the Han slit rheometer. In the analysis of the experimental data, the pressure gradient was used to determine the wall shear stress, and the exit pressure to determine the elasticity of the filled polymers. The study shows that the materials studied follow a power law in viscous behavior over the range of shear rates investigated and that the viscosity increases and elasticity decreases as filler concentration is increased. Also investigated was the effect of temperature on the viscoelastic properties of filled polypropylene melts.
99 citations
TL;DR: In this paper, the relation between shear stress and shear rate has been determined for elastohydrodynamic oil films, and it has been shown that the critical factor is the magnitude of the shear pressure, not the rate of shear, and that this critical magnitude depends upon the pressure and the molecular size.
Abstract: The relation between shear stress and shear rate has been determined for elastohydrodynamic oil films. At low values the rate of shear is directly proportional to the shear stress, but at higher values the shear rate increases more rapidly than the stress. It is shown that the critical factor is the magnitude of the shear stress, not the shear rate, and that this critical magnitude depends upon the pressure and the molecular size. Above the critical stress, in the non-Newtonian region, the shape of the curve relating the stress to the rate of shear depends upon the distribution of the sizes of the molecules in the oil. It is shown that in elastohydrodynamic conditions the limits of Newtonian behaviour are frequently exceeded and that this is liable to influence the pressure distribution, the magnitude of the traction, the generation of heat, and, at high speeds, the value of the film thickness.
69 citations
TL;DR: In this article, an experimental study of viscous heating in the flow of fluids with an exponential dependence of viscosity on temperature has shown that, for a given shear stress, two shear rates are possible.
Abstract: Theoretical investigations of viscous heating in the flow of fluids with an exponential dependence of viscosity on temperature have shown that, for a given shear stress, two shear rates are possible. Above a critical value, the stress decreases as the shear rate increases.
The present work is an experimental study of this phenomenon in plane and circular Couette flows and in cylindrical Poiseuille flow. ArochlorR 1260, a high viscosity Newtonian fluid with an extremely sensitive viscosity-temperature dependence is used as the test fluid. The results clearly show that two shear rates for Couette flow exist for one measured wall shear stress. Because of the viscosity-pressure dependence of the fluid, the Poiseuille flow results are inconclusive.
49 citations
TL;DR: In this article, the authors describe a Couette type rheometer which has been developed for measuring some rheological properties of fluid concrete mixes, with a discussion of experimental results.
Abstract: The description of aCouette type rheometer which has been developed for measuring some rheological properties of fluid concrete mixes is given with a discussion of experimental results. The instrument produces a recorded trace which is essentially a stress decay curve attributed to thixotropic breakdown of the material structure. This breakdown curve is predicted better by an expression of the power law type than of the exponential type. Analysis of the empirical flow curves shows that, despite some limitations in its essential geometry, the instrument reflects the flow behaviour of the full concrete mix. Up to rotational speeds of 26 r.p.m., the flow curves are typical ofBingham plastics. The yield values and plastic viscosities of the mixes which are very fluid and typical of piling concrete are of the order of 2.5–12.0 kN/m2 (or 25000–120000 dynes/cm2) and 5–40 kilopoises (5000–40000 poises) respectively. These quantities vary with concrete mix parameters, and increase exponentially with decrease in water/cement ratio.
20 citations
TL;DR: In this article, a relation between the melting temperature in shear (Tdyn), the static melting temperature (Tm), and the shear stress (τ) is found.
Abstract: The aggregates found in dilute solutions of nearly atactic PVC have been shown to consist of 10 to 15 single molecules held together by a crystalline nucleus. Based on the postulate that the last crystallites in a PVC melt have the same structure as found in dilute solution, a relation between the melting temperature in shear (Tdyn), the static melting temperature (Tm) and the shear stress (τ) is found:
where Q is a constant. The model predictions are in accordance with data from a Brabender rheometer and a Rheometrics mechanical spectrometer. Q is found to be a constant for samples with weight average molecular weights in the interval between 70,000 and 160,000 corresponding to polymerization temperatures between 40 and 70°C.
17 citations
01 Jan 1974
TL;DR: In this paper, the authors performed vane shear tests at varying rates of shear on three types of cohesive sediment: a clayey silt, a calcareous ooze, and a red clay.
Abstract: Vane shear tests were performed at varying rates of shear on three types of cohesive sediment: a clayey silt, a calcareous ooze, and a red clay. The shear strength was found to vary significantly for the range of shear rates typically used by researchers and practicing engineers. A standard rate of 0.0262 rad/s (90 deg/min) is recommended.
13 citations
TL;DR: In this article, two series of glass-reinforced diallyl phthalate molding compounds from two different manufacturers were evaluated using a Rheometrics Inc. Mechanical Spectrometer and a Brabender Torque Rheometer.
Abstract: Two series of glass-reinforced diallyl phthalate molding compounds from two different manufacturers were evaluated using a Rheometrics, Inc. Mechanical Spectrometer and a Brabender Torque Rheometer. Comparison of reactivity and minimum viscosity as measured by these two instruments is presented. The Mechanical Spectrometer appears capable of differentiating smaller changes in melt viscosity than does the Brabender Torque Rheometer.
12 citations
TL;DR: In this article, an annular die has been designed having a very thin gap distance between two coaxial cylinders, and the die was then used to measure wall normal stresses along the longitudinal direction of polymer melts flowing through the thin annulus.
Abstract: An annular die has been designed having a very thin gap distance between two coaxial cylinders. The die was then used to measure wall normal stresses along the longitudinal direction of polymer melts flowing through the thin annulus. The materials investigated were high-density polyethylene, low-density polyethylene, polypropylene, and polystyrene. Also investigated were blends of polystyrene and polypropylene, and blends of polystyrene and high-density polyethylene The measurements of wall normal stresses were used to determine the rheological properties of the melts, namely, the melt viscosity from the slope of axial wall normal stress profiles and the melt elasticity from exit pressures. The interpretation of the experimental data was made possible by the fact that the narrow-gap annular die can be considered as a substitute for a thin slit die. It has been found that the results obtained in the present study are consistent with those reported earlier by the author, who at that time used both capillary and slit dies.
11 citations
TL;DR: In this paper, a new method for direct shear tests was devised to measure easily the flow properties of a powder and a granular material, based on the stress resulted from expansion in volume of the specimen during a shear test.
Abstract: A new method for direct shear tests was devised to measure easily the flow properties of a powder and a granular material. This method is based on the stress resulted from expansion in volume of the specimen during a shear test.Expansion is caused by the movements of each particle in shearing zone. Such a stress increses with increased shear strain while expansion occurs. A yield locus is therefore obtained from a single shear test recording simultaneously the normal and the shear components of the stress by a X-Y recorder.The yield locus of the granular material is a straight line through the origin. The slope of this line, that is, the apparent coefficient of internal friction is depend on the height of the specimen. Therefore the true coefficient of internal friction is determined by extrapolating the height of the specimen toward zero. Furthermore, the cohesion and the unconfined yield strength of the powder are determined very easily from a single shear test in the region of low stress. The reproducibility of the results in the present method is satisfactory.
10 citations
TL;DR: The low shear rate viscosity behavior of SBR random copolymers is investigated in steady and transient shear flow in this article, and it is shown that the polymers exhibit non-Newtonian steady shear viscosities.
Abstract: The low shear rate viscosity behavior of SBR random copolymers is investigated in steady and transient shear flow. The polymers studied have high enough molecular weights to make them of commercial interest. The measurements were performed on an apparatus specially designed but readily available and easy to operate. The results showed that even at very low shear rates, the polymers exhibit non‐Newtonian steady shear viscosities. A log‐log plot of zero shear rate viscosity vs weight‐average molecular weight yields a straight line of slope 3.5. The transient shear data show no stress overshoot at shear rates when the viscosity is non‐Newtonian. A theoretical discussion of the independence of these two nonlinear effects is provided. The discussion is based on some popular single‐integral constitutive equations. It is shown that a recent modification by Carreau to the Lodge elastic liquid model is very realistic. That is, Carreau's model allows one to obtain separately transient shear stress overshoot and non‐Newtonian steady shear viscosity.
10 citations
TL;DR: In this article, an instrument was developed for the direct measurement of the local shear stress on the surface of circular cylinders, where an element of the cylinder surface was suspended in such a way that under the effect of a shear force it was free to move a small amount in the direction of flow.
Abstract: An instrument has been developed for the direct measurement of the local shear stress on the surface of circular cylinders. An element of the cylinder surface 50.8 mm long and 3.18 mm wide is suspended in such a way that under the effect of a shear force it is free to move a small amount in the direction of flow. This movement is calibrated in such a way to indicate the magnitude of the frictional force. The instrument was tested on a cylinder 89 mm in diameter; the results proved that the device is accurate, efficient and reliable.
TL;DR: In this article, a rotational rheometer capable of making accurate measurements of steady shearing viscosity and first normal stress difference, eccentric disc mode testing forG′ andG″, transient measurements of shear, and sinusoidal time-shearing or other time-varying input measurements; a wide variety of these may be programmed.
Abstract: Recent work in rheology has indicated a need to explore, on a routine basis, methods of testing viscoelastic fluids beyond the measurement of steady shearing viscosity. In particular, measurements in transient flows (starting and stopping of shear) and the investigation of the flow between eccentric discs and cylinders as an alternative to time-oscillatory shear testing are current topics of great interest. The present paper discusses the design philosophy and proof testing of a new rotational rheometer capable of making (i) accurate measurements of steady shearing viscosity and first normal stress difference; (ii) eccentric disc mode testing forG′ andG″; (iii) transient measurements of shear and first normal stress difference; (iv) sinusoidal time-shearing or other time-varying input measurements; a wide variety of these may be programmed. Tests illustrating the machine capabilities are shown for several fluids. The machine is designed to work accurately over a wide range of materials from polymer melts to dilute solutions and over adequate shear rate and temperature ranges. The desire to measure transients inevitably leads one to consider a stiff machine. In the measurement of transient normal thrusts, difficulties arise in a cone-plate device because of the “squeeze-film” effect in a real machine with finite stiffness. We conclude that the use of rotating eccentric discs is an attractive alternative to sinusoidal testing and, with proper safeguards, gives accurate results forG′ andG″.
TL;DR: In this paper, a master curve was constructed from such data obtained at various speeds using a principle of corresponding states, which closely resembles the steady-state viscosity curve and at high shear rates joins the complex viscoity curve measured with the Rheovibron.
Abstract: Because the Mooney Rheometer is widely used and accepted in the laboratory and the plant a closer examination of what it measures is warranted. Although the steady torque value has been converted to steady-state viscosity, the “Mooney torque—time curve” has not been reduced to fundamental parameters. This work, carried out with SBR 1500, treats the initial torque rise as the shear stress-strain behavior analogous to tensile stress-strain. A master curve was constructed from such data obtained at various speeds using a principle of corresponding states. The master curve closely resembles the steady-state viscosity curve and at high shear rates joins the complex viscosity curve measured with the Rheovibron. In addition the use of the transient data enables one to extend the low shear end of the viscosity-rate curve by two decades. The peaks of the torque—time curves strongly suggest that they represent failure points of the material.
TL;DR: In this article, a new method was found for determining the complete set of viscometric functions characterizing the steady shear flow of non-Newtonian liquids, viz. the shear stressτ, and the first and second normal stress differencesN1 andN2.
Abstract: A new method has been found for determining the complete set of viscometric functions characterizing the steady shear flow of non-Newtonian liquids, viz. the shear stressτ, and the first and second normal stress differencesN1 andN2. The method is based on a modified cone-and-plate flow system and requires only one relatively simple experiment to obtain the data from whichτ, N1 andN2 are derived.
TL;DR: In this article, a rheological investigation of saturated fatty acids as lubricants for PVC was made in a Sieglaff-McKelvey rheometer over a wide temperature range.
Abstract: A rheological investigation of the saturated fatty acids as lubricants for PVC was made in a Sieglaff-McKelvey rheometer over a wide temperature range. Results reveal that with an increase in carbon chain, fatty acids became more effective in reducing the melt viscosity of PVC. It was also discovered that the maximum viscosity variation due to these materials was observed at 350°F. At test temperatures of 400°F and above, no major viscosity differences were observed. Furthermore, the changes in the melt viscosity were more pronounced at shear rates less than 200 sec−1. The usefulness of the measured viscosity variations at the critical test temperature of 350°F was shown by extrusion. An excellent correlation between the apparent melt viscosity and extrusion melt temperature was found. The criticalness of the test temperature in assessing the effect of lubricants on PVC flow is discussed.
TL;DR: In this article, a flat plate rheogoniometer was used to measure the shear stress and the primary normal stress difference (N1=T11−T22) for polyethylene oxide (Mw=4×106) solutions.
Abstract: Important rheological properties of viscoelastic fluids can be obtained by studying continuous flow through a channel approximating infinite parallel plates. This flat plate rheometer eliminates or reduces some problems of conventional ones and extends the region of useful measurements to high shear rates. Four pressure transducers are flush mounted on the top plate to measure the normal stress T22. From these measurements the shear stress can also be obtained. The normal stress in the direction of flow (T11) is obtained from the measurement of the impact of the exit stream. A Weissenberg rheogoniometer (WRG) is used to measure the shear stress and the primary normal stress difference (N1=T11−T22). Data are presented for polyethylene oxide (Mw=4×106) solutions of 0.25%, 0.9%, 2.0%, and 3.0% in water. Newtonian fluids were used to test and compare the apparatus. Fluid viscosities from 0.01 to 6000 poise and normal stresses from 100 to 450,000 dynes/cm2 were determined for shear rates from 0.03 to 130,000 sec−1. The rotational geometry of the WRG limits its use to shear rates under 102–103 sec−1. Further, the precision of normal stress measurement with the parallel plates is better than obtained with the WRG. The shear stress values obtained with the plates are of equivalent precision and higher accuracy. Normal stress dependence upon shear rate is fit by the molecular dumbbell model of Bird et al. over a wide range of conditions. In the upper region the model predicts a slope of 2/3 and 0.66±0.03 is obtained by regression analysis of the data. In the lower region a slope of 2 is predicted and 2.08±0.37 obtained. Extrapolation of T11 and T22 data using this model allows N1 to be obtained at shear rates far higher than with the WRG. The magnitude of the ratio T22/T11 decreases as Polyox concentration increases and the fluid becomes more elastic. The complete state of stress is determined for all Polyox solutions, and pressures at the exit surface and exit centerline are found to contribute substantially to the total stress tensor.Important rheological properties of viscoelastic fluids can be obtained by studying continuous flow through a channel approximating infinite parallel plates. This flat plate rheometer eliminates or reduces some problems of conventional ones and extends the region of useful measurements to high shear rates. Four pressure transducers are flush mounted on the top plate to measure the normal stress T22. From these measurements the shear stress can also be obtained. The normal stress in the direction of flow (T11) is obtained from the measurement of the impact of the exit stream. A Weissenberg rheogoniometer (WRG) is used to measure the shear stress and the primary normal stress difference (N1=T11−T22). Data are presented for polyethylene oxide (Mw=4×106) solutions of 0.25%, 0.9%, 2.0%, and 3.0% in water. Newtonian fluids were used to test and compare the apparatus. Fluid viscosities from 0.01 to 6000 poise and normal stresses from 100 to 450,000 dynes/cm2 were determined for shear rates from 0.03 to 130,000 ...
TL;DR: In this paper, the authors consider nonstationary shear flow of a viscoplastic medium between two parallel plates and also in a cylindrical tube under the action of a time-varying shear stress applied to the walls of the passage.
Abstract: We consider problems involving nonstationary shear flow of a viscoplastic medium between two parallel plates and also in a cylindrical tube under the action of a time-varying shear stress applied to the walls of the passage.
TL;DR: In this paper, the authors describe an instrument which has been designed to measure the components of the complex shear modulus in the frequency range 10−3-50 Hz for high molecular weight polymers.
Abstract: Previous work in the author’s laboratory has been largely concerned with the study of the visco-elastic properties of supercooled liquids and polymers of relatively low molecular weight (1, 2). Measurements on these materials can conveniently be made in the frequency range 104 to 109 Hz. In extending the scope of the research to include the study of high molecular weight polymers it has been necessary to develop apparatus to enable results to be obtained at lower frequencies. This paper describes an instrument which has been designed to measure the components of the complex shear modulus in the frequency range 10−3–50 Hz.
TL;DR: In this article, a master curve encompassing 13 decades of time was constructed using data from Mooney rheometer shear stress-strain, MTS high speed tensile stress strain, and the Rheovibron, representing the rubbery region of viscoelastic behavior in terms of time, temperature and the magnitude of deformation up to the breaking point.
Abstract: The dynamic viscoelastic properties of four samples of butadiene—acrylonitrile raw elastomers, were obtained with a Rheovibron at 110 Hz and temperature range of −80 to 160°C. The complex properties were in agreement with the master curves obtained previously from stress-strain measurements. A master curve encompassing 13 decades of time was constructed using data from Mooney rheometer shear stress-strain, MTS high speed tensile stress-strain, and the Rheovibron. The master curve represents the rubbery region of viscoelastic behavior in terms of time, temperature, and the magnitude of deformation up to the breaking point. This study demonstrates that corresponding states can be found between small (ca. 1 per cent) and large deformation up to break (e.g., 1400 per cent).
TL;DR: In this paper, a new approach based on the elementary theoretical interpretation of experimental data is adopted in order to obtain a unique relationship for turbulent flow, in particular, wall shear stress is found to be a unique function of a new turbulent pseudo shear rate term.
Abstract: A unique shear stress-shear rate relationship exists for laminar flow of any time independent substance in a tube, whereas this is not the case for turbulent flow. In order to obtain a unique relationship for turbulent flow, a new approach based on the elementary theoretical interpretation of experimental data is adopted in the present paper. In particular, wall shear stress is found to be a unique function of a new turbulent pseudo shear rate term. In this relationship there are two parameters which characterize a given substance — the limiting viscosity at high shear rateµ
m and a factorα
m which takes into account modification of turbulent structure by the non-Newtonian properties. Both of these parameters must be determined experimentally. Methods of predicting pressure gradients and of scaling up are outlined. In applying the approach to suspensions in which the solid phase has a density greater than that of the liquid medium, it may be important to determine the increment in shear stress equivalent to the energy required to maintain the solid particles in suspension. The validity of this approach is confirmed by data for the flow of a variety of substances including kaolin suspensions and Carbopol solutions in tubes ranging in diameter from 1.5 to 20 mm.
TL;DR: In this paper, the authors used the Contraves balance rheometer to measure the viscosity, shear modulus, and loss angle of the plastisols used for gelation and fusion.
Abstract: The Contraves balance rheometer has been used in a study of the gelation and fusion process of three DOP-based PVC-plastisols and the results compared with those obtained with the Brabender plastograph. The tensile properties of samples fused at different temperatures have also been determined. The rheometer results relate to the temperature dependence of the viscosity, shear modulus, and loss angle of the plastisols used. The viscosity- and modulus-temperature curves are to some extent reminiscent of the torque-temperature curves obtained with the plastograph; the fusion temperatures are slightly different. The loss-angle-temperature curves measured with the rheometer exhibit sharp maxima in the vicinity of the Tg-point of the base polymer. The shear modulus decreases with time when the temperature is kept constant (above the fusion point). This effect is possibly associated with crystallite melting. The temperature necessary to reach the maximum strength plateau of films fused at various temperatures was found to agree (within 10°C) with the maximum in the modulus-temperature curves (minimum in loss-angle-temperature curves) when the rheometer shear rate was sufficiently low. On the whole, the rheometer allows for better temperature control. Also, the fact that the results are given in terms of viscosity and shear modulus may have some advantage in interpreting gelation and fusion data.
TL;DR: In this paper, an experimental investigation of the combined periodic axial and shear deformation of polymers in the viscous-flow state was conducted, and it was shown that nonlinear shear deformations affect axial viscoelastic properties and nonlinear axial deformation affects the shear properties of the material.
Abstract: Results are given of an experimental investigation of the combined periodic axial and shear deformation of polymers in the viscous-flow state. Specimens in the form of right cylinders were disposed between two parallel plates to which the material adhered completely. The experimental data are compared with those obtained under simple shear. The results indicate that, with combined periodic axial and shear deformation, nonlinear shear deformations affect the axial viscoelastic properties and nonlinear axial deformations affect the shear properties of the material.