摘要:

The birefringence in injection molds of noncrystalline linear polymers arises from two different kinds of deformation; one incorporated with the change of intersegmental distance and one with the deformation of molecular conformation. Their contributions to birefringence were separately observed in injection‐molded polystyrene. The birefringence originating from the molecular‐conformational deformation was compared with computer simulation results, in which the rheology constitutive equation of Leonov was employed to calculate the shear and the normal stresses.

ISSN:0148-6055    

DOI:10.1122/1.550426

出版商:The Society of Rheology    

年代:1993

数据来源: AIP

摘要:

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 was 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.

ISSN:0148-6055    

DOI:10.1122/1.550428

出版商:The Society of Rheology    

年代:1993

数据来源: AIP

摘要:

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 thicknesses. When surface roughness of dies was 0.1 μm, 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 2 to 10 μm. Over 10 μm of the roughness the apparent slip velocity became zero. Therefore the thickness of the slip layer was supposed to be within several microns.

ISSN:0148-6055    

DOI:10.1122/1.550430

出版商:The Society of Rheology    

年代:1993

数据来源: AIP

摘要:

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 velocityValong the vessel lengthyand the width δ of the upflow layer at tilt angles θ of 10°, 20°, 40°, and 60°. Sample was a swine erythrocyte suspension at nonaggregated 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. BothVand δ increased with increasing θ. The observed velocity profiles were represented by the reduced equation 1−V/Vmax=(1−x/δ)2as predicted by the Acrivos and Herbolzheimer theory. Here,xis a coordinate taken along the end line at the bottom of the vessel.

ISSN:0148-6055    

DOI:10.1122/1.550432

出版商:The Society of Rheology    

年代:1993

数据来源: AIP

摘要:

The second normal stress is measured for aqueous solutions of Separan with polymer weight fraction from 1% to 3% and for 10−2mol/laqueous cetyltrimethylammonium bromide (CTAB) solution containing 1.5×10−2mol/lof 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.

ISSN:0148-6055    

DOI:10.1122/1.550433

出版商:The Society of Rheology    

年代:1993

数据来源: AIP

摘要:

The concentration dependence of characteristic time τrfor self‐diffusion coefficientDsof linear polymers in good solvents was discussed in comparison with that of the weight average relaxation time τwfor viscoelastic properties. Similarities were found for the concentration regions of τrand 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 theDsdata of polymers at finite concentrations so far published should not be discussed in terms of the reptation model since the solutions are not regarded as those in the well entangled regions.

ISSN:0148-6055    

DOI:10.1122/1.550382

出版商:The Society of Rheology    

年代:1993

数据来源: AIP