A research project undertaken during the period of 1960-1969 by the “Bussei Group”of Japan Synthetic Rubber Co. was reviewed, and the prologue and the epilogue for this long term project were presented. The overall framework was first shown as the target system of the project which aimed in correlating the quality of rubber products with the molecular characteristics of raw rubbers. Eight principal research areas were then identified to develop the subsystems which constitute the total system. For each of the research areas, a general way of approach to the rheological problems was shown and then some typical examples of the results thus obtained were illustrated. Finally, in the prologue, a review of the historical background of this research project was given, and in the epilogue, the reason by which this project had to come to an end was examined from a managerial point of view.
Drag reduction caused by the injection of polymer solution into a turbulent pipe flow was investigated by means of a flow visualization technique. Turbulent fluctuating velocity in a drag-reducing flow was determined by a tracer method. It became evident from the experimental results that the defect of Reynolds stress existed over the wide range of the radial position in a polymer drag-reducing pipe flow. The optimum preparation method of coal water mixtures (CMW) has been developed. The present study contributed to the successful production of highly loaded CMW with lower viscosity. An evaluation method of the dynamic stability during the transportation of CWM was proposed. This method was based on a thixotropy model for slurries, and it was successfully used for the estimation of dynamic stability of CWM with a laboratory stability test.
The slip velocity of molten rigid PVC was investigated. Using Mooney's method, slip velocity was obtained from flow curves which were measured by slit dies with different thickness. When surface roughness of dies was 0.1μm, the slip velocity logarithmically increased with shear stress. When an extrusion temperature was 180°C, the slip flow was dominant and the ratio of slip velocity to mean velocity was about 90%. Its ratio decreased with increasing extrusion temperature. The slip velocity rapidly decreased when the surface roughness was increased from 2μm to 10μm. Over 10μm of the roughness the apparent slip velocity became to zero. Therefore the thickness of the slip layer was supposed to be within several microns.
Numerical simulation of viscoelastic flow at high Weissenberg number (We) was carried out by the streamline-upwind finite element method with the sub-elements for stress components proposed by Marchal and Crochet. This method and the Galerkin finite element method were applied to the stick-slip flow with the singular point in order to examine the effectiveness of this method. The Oldroyd-B model was used as a constitutive equation. This model incorporates strong elasticity and numerical solutions sometimes diverge. When the Galerkin finite element method was used, the numerical solutions had oscillation and the loss of convergence occurred at relatively low value of We. On the other hand, when the streamline-upwind method was used with the stress sub-elements, the oscillation of numerical solutions did not appear and the solution could be obtained up to a high value ofWe. Using the latter method, the calculation of the tapered contraction flow was carried out with the Giesekus model as a constitutive equation. The limit values of We were not encountered and we could calculate even at We> 100 using various values of model parameters. It was concluded that the streamline-upwind finite element method with the stress sub-elements was very useful to simulate the contraction flow up to high values of We.
In order to clarify the relation between the enhanced erythrocyte sedimentation rate in an inclined vessel and the medium upflow underneath the downward-facing wall of the vessel, we have measured the upflow velocity V along the vessel length y and the width δ of the upflow layer at tilt angles θ of 10°,20°,40°and 60°.Sample was a swine erythrocyte suspension at non-aggregated state at the volume fraction of 0.2. Polystyrene latex particles with 1 μm diameter were mixed in the suspension to visualize the motion in the upflow layer. Observations were made with a video system under an invert microscope at room temperature. The upflow layer began to be formed immediately after the sample injection, and reached to the steady state within 10 min, while keeping a thin layer. The time for reaching the steady state decreased with increasing θ. The upflow velocity was much higher by two to three orders of magnitude than the sedimentation rate. Both V and δ increased with increasing θ. The observed velocity profiles were represented by the reduced equation 1-V/Vmax=(1-χ/δ)2 as predicted by the Acrivos and Herbolzheimer theory. Here, χ is a coordinate taken along the end line at the bottom of the vessel.
The second normal stress is measured for aqueous solutions of Separan with polymer weight fraction from 1% to 3% and for 10-2 mol/l aqueous cetyltrimethylammonium bromide (CTAB) solution containing 1.5×10-2 mol/l of sodium salicylate (NaSal) as an added salt. The measuring device is a newly developed one composed of two parallel plates vertically set and opened to the atmosphere at the sides, and the solution is made to flow down through the slit between the two parallel plates by the gravity.The torque on one of the plates induced by the flow is measured and the second normal stress difference is estimated. The second normal stress difference obtained is negative for Separan solutions, and its absolute value is found to be of the same magnitude as the shear stress. For the CTAB: NaSal aqueous solution, the second normal stress difference is negative and the magnitude is larger than the values for Separan solutions. Its absolute value is 1-10% of the first normal stress difference.
This paper describes a detailed study on effects of moisture and solid phase polymerization on melt viscoelastic properties of poly (ethylene terephthalate) (PET). We found a drying condition and an experimental procedure which did not induce any variation of either molecular weight or molecular weight distribution in samples during periods of sample preparation and a short time run of viscoelastic measurements. For a long time run, η′ and G′ increased with time and especially the increase of the latter was remarkable. The similar behaviour was observed for nylon-66 but not for poly (butylene terephthalate) (PBT). It is suggested that highly branched and/or cross-linked substances were produced in the samples besides linearly polymerized ones.
The concentration dependence of characteristic time τr for self-diffusion coefficient Ds of linear polymers in good solvents was discussed in comparison with that of the weightaverage relaxation time τw for viscoelastic properties. Similarities were found for the concentration regions of τr, and τw, and also for the concentration dependences of τ's in the respective regions. On the basis of the similarities, it is pointed out that almost all the Ds data of polymers at finite concentrations so far published should not be discussed in terms of the reputation model since the solutions are not regarded as those in the well entangled regions.