The present study is an experimental investigation of the effects of hydrostatic pressure on the capillary flow behavior of a polystyrene melt by using an Instron type rheometer with a two-stage capillary. The results may be summarized as follows: (1)The relations between the pressure losses in the first and second capillaries are given by the following equations Δp1=Δptot-Δp2 (a) Δp2=pn (b) where, Δp1 and Δp2 are the pressure losses in the first and second stages, respectively, Δptot is the total pressure loss, which nearly equals the applied pressure p, and pn is the hydrostatic pressure induced by the second capillary. Since the sample is compressed in the first stage by the pressure pn, which is estimated by equation (b), it is possible to make an experimental study of the effects of hydrostatic pressure. (2) The ratio of the viscosity coefficients for hydrostatic pressure flow to that for atmospheric pressure flow η′n/η′o is approximately given by the following equation. _??_ (c) where, K1 and N are material constants. (3) The pressure loss due to the elasticity effect of the specimen at the capillary inlet, under the influence of the hydrostatic pressure, is given by the following eqution _??_ (d) where, ΔpE.0 is pressure loss at the capillary inlet under hydrostatic pressure, ΔpE.0 is that under stmospheric pressure, Δυ/υ0 is the volumetric strain, A and K2 are material constants.
The change of the gelation state of PVC particles during mixing with a Brabender plastograph was observed by eye and with an electron microscope. At the same time mixtures with different degrees of gelation were prepared with reference to the torque curve, and the effect of the degree of gelation on the capillary flow properties was examined by means of a Koka flow tester. At the peak position of the torque curve, gelation was incomplete and some particle structure still remained.At a position a little past the peak, a honogeneous structure was attained and gelation was complete. With increasing gelation, the viscosity increased and also the Barus effect and melt fracture distortions, which are due to melt elasticity, became more noticeable. Moreover, these properties were more pronounced in a material prepared by a tin formulation than in one preparcd by a lead formulation; the former is easier to gelate than the latter. These experimental results support Berens's hypothesis namely, that an increase of gelation couses the particle flow mechanism to shift to a homogeneous flow mechanism, with a resulting increase ih the viscosity and elasticity. However, the end correction coefficient, which is another measure of elasticity in capillary flow, decreased with an increase of gelation and was larger in the lead formulation that in the tin formulation. Consequently, it may be assumed that the end correction coeffcient is an inadequate measure of elasticity, at least in materials such as PVC compounds which have inhomogeneous structure and exhibit dilatant flow behavior.
Volcanic ash soil in Japan is principally composed of allophane, with some quantities of various layer silicates, gibbsite, and other sesquioxide minerals. In the Kanto district a type of volcanic ash soil called Kanto loam is found. This soil shows thixotropic response upon remolding. In the natural state, Kanto loam has a porous structure with good bearing capacity but after remolding, the strength is lowered and the structure is broken. In this work the thixotropic properties of Kanto loam in the gel state obtained by adding, cations (Na+, K+, NH4+ and H+) were investigated by the use of consistency curves and centrifugal dehydration curves for soil water. The cation adsorption of allophane is considered to be not of the interlayer type but of the surface adsorption type. A cation can be added to the soil by normal methods (chloric salts, but hydrochloride in the case of H+). The important results may be summarized as follows. The flow properties of a water suspension gel of the fresh soil show generally more thixotropy than do air dried soils. It is found that the flow and dehydration behaviour of a K+ soil and a NH4+ soil more similar to each other than the corresponding behaviour of K+ and Na+ soils. This must be also related to the ionic behaviour of the soil, in the sense that K+ and NH4+ are easily fixed to allophane soil, or freed from it, depending on the surrounding chemical condition. It is supposed that an external force would be effective in changing the adsorption condition of the allophane surface.
Anisotropic, three-dimensional consolidation tests were conducted on organic clays and an attempt was made to represent the resulting complex phenomena in terms of as simple an equation as possible. Basic experimental data, involving relationships between stress, strain, and time, were used to develop the equation. The conclusions obtained are as follows: (1) The shear creep rate during anisotropic consolidation may be expressed by a linear equation in terms of the stress ratio. Creep rate in anisotropically consolidated samples is more sensitive than in isotropically consolidated ones to a variation of stress ratio. The safety factor for the flow creep failure of isotropic samples is apt to be overestimated. (2) In contrast to the case of isotropic consolidation, the dilatancy cannot be ignored in the case of anisotropic consolidation. The dilatancy rate can be expressed by Eq.(15) shown in the paper.
The stress relaxation behaviour of a gluten-water mixture, which was prepared by mixing the dried gluten protein with water in the weight ratio gluten: water=1: 0.5, was studied to simulate the properties of wheat flour dough. The rheological properties of wheat flour dough are complex ones, but it is believed that the gluten-water system is a good model for the continuous phase of the dough. The results obtained can be summarized as follows: (1) The gluten-water system shows linear viscoelastic response. (2) The addition of a small amount of the reducing agent glutathione is effective in softening the system above a temperature of 20°C; this suggests that an interchange reaction between -SH and -SS- in the gluten is induced at relatively high temperatures. (3) Since the presence of an electrolyte also has an effect on the rheological properties of the system, one needs to use various salt concentrations to fully understand the phenomena involved. Future work will be directed toward studying the interaction mechanism between gluten protein and various electrolytes.
The dynamic viscoelastic properties of several liquid crystal states of cholesteryl myristate were studied. Cholesteryl myristate was selected as a material for study because it appears both in the form of cholesteric liquid crystals and smectic liquid crystals, depending on the temperature. At small strain amplitudes, the dynamic viscoelastic properties were measured by means of a coaxial cylinder rheometer in the angular frequency range 0.23-2.96 sec-1, in the temperature range 70-80°C. Hysteresis loops for the cholesteric state change with frequency and show a non-linear pattern at the higher frequencies. Both the storage modulus G′ and the loss modulus G″ for the cholesteric state change with frequency. In contrast, the absolute modulus |G| for the smectic state does not change with frequency and the liquid crystal behaves as an elastic solid. At large strain amplitudes, the dynamic viscoelastic properties were measured by means of a cone-plate rheometer in the angular frequency range 0.135-5.39 sec-1, in the temperature range 90-50°C. Hysteresis loops for this material at a fixed frequency change with temperature. The hysteresis loops for the cholesteric state are elliptical, which is typical linear viscoelastic response, but for the smectic state, they are very much distorted. It has been pointed out that the dynamic behavior of liquid crystals is very strongly affected by their mechanical histories. And even cholesteric liquid crystals show liquid-like flow behavior after many cycles of sinusoidal strain. Although such rheotropic phenomena are very complicated ones, preliminary studies indicate that they are more evident in the cholesteric state than in the smectic state. Data were compared after 10 cycles of sinusoidal strain at a frequency of 0.27 sec-1. The dissipation energy ED for the cholesteric state increases with frequency in a somewhat different way from that for the smectic state. For the smectic state ED0, the extrapolated value of ED at zero frequency, decreases with increasing temperature.
Dispersions of stearic acid in an aqueous phase containing polyhydric alcohol, stabilized by sodium and potassium soaps, have been studied by measuring their flow and creep properties. The stearic acid was a commercially available mixture of the long chain acids of C14, C16, C18 and C20; the polyhydric alcohol was a member of the series glycerin, propylene glycol, etc. All the systems examined showed complex flow properties, e. g., hysteresis loops and spur points in the flow experiments. The creep behavior of all the systems could be represented by a me chanical model composed of a Voigt unit and a Maxwell unit in series. The observed total compliance was markedly dependent on the formulation and the aging time of the systems. However, the retardation time did not change appreciably, indicating that there was no essential difference in the nature of the secondary bonds in the systems, which break and reform during creep tests.
The dynamic mechanical properties of poly (γ-methyl L-glutamate) (PMLG) fibers and films were observed. The undrawn fiber and films, which were found to have an α-helical conformation, showed a maximum in the dynamic loss E" curve at 150-160°C. This dispersion was assumed to be due to the slipping motion of the unoriented helices in the amorphous region. The fiber sample slowly drawn at 150°C and also the oriented film exhibited another maximum in the E″ curve at above 180°C. This maximum was assigned to a slipping motion in the crystalline region. The cold-drawn fiber was found to be mainly in the β-form and showed a maximum in the E″ curve at about 100°C. This dispersion was assigned to a segmental motion in the random-coil region. The conformation of PMLG in films cast from the random-coil solvents, dichloroacetic acid and trifluoroacetic acid (TFA), was found to be α-helical. It was assumed that the transformation from random-coil to α-helical occurred in the casting process. The film cast from TFA-formic acid was mainly in the β-form. But a contribution of the random-coil region to the dynamic mechanical dispersion was not found.