摘要:

Diverging radial flow between parallel plates was studied under isothermal steady‐state conditions. Flow ratesQand radial pressure distributionsp(r)were measured for one Newtonian liquid and three non‐Newtonian polymer solutions. The powerlaw viscosity model, with parameters evaluated from cone‐and‐plate viscometry, was remarkably good in fittingQ(Δp)data and, in most cases, also for describingp(r).Thus, for these polymer fluids with only moderate viscoelasticity (Weissenberg number<1), more sophisticated rheological modeling is not needed for predicting flow rate and pressure distributions. However, tracer experiments hinted at the presence of instabilities and/or secondary flows.

ISSN:0148-6055    

DOI:10.1122/1.549339

出版商:The Society of Rheology    

年代:1974

数据来源: AIP

摘要:

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.

ISSN:0148-6055    

DOI:10.1122/1.549358

出版商:The Society of Rheology    

年代:1974

数据来源: AIP

摘要:

Stress relaxation of a reinforced vulcanized styrene‐butadiene (SBR) elastomer after simple elongation has been investigated over a range of strains and at several filler levels. Carbon blacks and starch xanthide were the reinforcing agents studied. Double logarithmic plots of load versus time at constant strain were linear over five decades in time, the slope being relatively insensitive to either filler type or loading level, except at low extensions or near the ultimate elongation level. The apparent relaxation time, given as the ratio of a viscosity, η, to a modulus,E, is thus independent of filler. Ratios(ηf/ηu)and(Ef/Eu),where the subscriptsfandurefer to filled and unfilled material, respectively, must show the same functional dependence on filler loading level. The usual two constant Mooney plots of[load/(λ−λ−2)]versusλ−1,where λ is the extension ratio, were highly nonlinear, rising steeply asλ−1approached unity, particularly for starch xanthide reinforced elastomers. Modulus ratio versus volume fraction plots suggest that the rigid phase, mechanically, is the continuous phase in starch xanthide reinforced elastomers.

ISSN:0148-6055    

DOI:10.1122/1.549340

出版商:The Society of Rheology    

年代:1974

数据来源: AIP

摘要:

The viscoelastic properties of dilute solutions of comb‐shaped branched polymers have been calculated from the bead‐spring model, following the Zimm and Zimm‐Kilb theories, with exact numerical evaluation of eigenvalues by the method of Lodge and Wu. Eigenvalues, relaxation times, and frequency dependence of the reduced intrinsic shear moduli[G′]Rand[G″]Rhave been obtained for various combinations of number of branch points(f)1 to 10, beads per branch(Nb)1 to 37, backbone beads between branches(Na)1 to 22, and the reduced hydrodynamic interaction parameter(h*)0 to 0.25. Since the total number of beads(f+1) Na+fNa+fNb−1is restricted to an unrealistically small value of 111 by computer limitations, attention is focused on the low‐frequency behavior where this restriction will have the least influence. Here, the behavior is characterized by the reduced steady‐state shear compliance. This quantity is quite sensitive tofwhen the mass backbone fraction λ is small (approaching starshaped geometry); and for larger λ, it can detect the presence of a small number of branches.

ISSN:0148-6055    

DOI:10.1122/1.549359

出版商:The Society of Rheology    

年代:1974

数据来源: AIP

摘要:

Reported herein are a theoretical treatment and an experimental investigation that deal with the interpretation of data from a pulse propagation test on a frequency‐dependent clay soil. A transfer function, which considers the superposition of an instantaneous response and the various modes of vibration, is obtained to relate the stress at the fixed end of a specimen to that at the input end, and the modulus of elasticity and viscosity are deduced from analyses of the fundamental resonant frequency of the specimen. Experimental data from shock tube tests on a clay soil provide a means for comparing the analytical predictions with the actual response. It is shown that use of the intuitively defined arrival time of a pulse yields values far too high for the modulus of elasticity, and higher values of damping and shorter lengths of specimen both contribute to making the results more unpredictable. Both the modulus of elasticity and the viscosity of the clay are found to be strongly dependent on frequency, the former increasing and the latter decreasing with increasing frequency.

ISSN:0148-6055    

DOI:10.1122/1.549341

出版商:The Society of Rheology    

年代:1974

数据来源: AIP

摘要:

A modified capillary rheometer and a motion‐picture camera are used to simultaneously record the pressure at the inlet to the tube, the flow rate through the tube, and the flow patterns in the barrel prior to the entry to the tube. Measured flow curves, employing tubes in the range14.7⩽L/D⩽36.7for a medicinal grade liquid paraffin in the range200⩽γ⩽4000 sec−1and a highly elastic solution of Separan AP 30 in the range100⩽γ⩽1500 sec−1,agreed well with the data obtained using a Haake Rotovisco cup and bob viscometer. Motion pictures of the flow patterns in the barrel for the Separan solution showed that the stable converging flow field at low flow rates developed a spiraling instability whose intensity increased with increasing flow rates until a complete breakdown of the flow field occurred at high flow rates prior to a second stage stability. Representative flow patterns in the range40⩽4Q/ΠR3⩽5154 sec−1are presented forL/D=36.7which show the behavior over the entire spectrum of shear rates including the second‐stage stability. The similarities of the flow patterns to those observed for polymer melts during extrusion are discussed in detail.

ISSN:0148-6055    

DOI:10.1122/1.549342

出版商:The Society of Rheology    

年代:1974

数据来源: AIP

摘要:

The viscosity behavior of colloidal asbestos fibril dispersions, in the presence of a polystyrene copolymer latex, was investigated over a range of shear rates using a Ferranti‐Shirely cone‐and‐plate viscometer. Flow of the asbestos suspensions was highly dependent on shear rate and time; the apparent viscosity was reduced when aluminum trichloride, an effective agent for separating the fibrils, was added. This effect was not seen when poly(acrylic acid) (PAA) was added instead. The complex dispersions containing a relatively low fraction of latex had a high apparent viscosity and were markedly thixotropic. As the fraction of latex increased, the behavior approached that of the unmodified latex. This had a small yield stress, but was otherwise nearly Newtonian. At high shear rates, the increase in viscosity due to addition of asbestos fibrils to the latex was relatively small.

ISSN:0148-6055    

DOI:10.1122/1.549343

出版商:The Society of Rheology    

年代:1974

数据来源: AIP

摘要:

The stress state of four rheologically characterized polymer melts—low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polystyrene (PS), and poly(methyl methacrylate) (PMMA)—in laminar shearing flow was completely determined by measuring the non‐Newtonian viscosity μ and the first and second normal stress differencesN1andN2.The meanN2function was negative and about 0.1–0.3 the value ofN1.The measurements were made in a Weissenberg rheogoniometer using cone‐ and parallel‐plate geometries. Additional viscosity measurements were made in a capillary rheometer. An experimental study of interface distortion in the stratified two‐phase flow has been carried out using these melts. It was found in the stratified flow experiments that the lower viscosity melts exhibited concave interfaces and encapsulated the higher viscosity melts irrespective of the relative values ofN1andN2.The rate of interface distortion and encapsulation increases with increasing viscosity differences. The pressure losses for stratified flow tended to be close to the values for the lower viscosity phase, especially for long dies. The problem of instabilities at the interface between the two melts is briefly discussed.

ISSN:0148-6055    

DOI:10.1122/1.549344

出版商:The Society of Rheology    

年代:1974

数据来源: AIP