ISSN:0148-6055    

DOI:10.1122/1.549134

出版商:The Society of Rheology    

年代:1969

数据来源: AIP

摘要:

The melt viscosity of narrow distribution, linear, random copolymers of butadiene (75%) and styrene (25%) prepared by anionic polymerization was investigated in both the Newtonian and non‐Newtonian regimes of flow. The Newtonian viscosity is shown to obey the usual 3.4th power dependence onMwThe temperature dependence is represented satisfactorily by the Vogel equation, as modified by Berry and Fox. Non‐Newtonian viscosities are reduced to a single master curve for all polymers, temperatures, and shear rates, using the Newtonian viscosity as the sole shift factor (η/η0vs.η0γ̇). Comparison of this master curve with those of two narrow distribution polybutadienes of different microstructure produces agreement within 0.2 of a logarithmic unit on theη0γ̇‐scale. All three master curves lie one to two decades toward higher reduced shear rates than various “universal” curves reported in the literature for polymers of broader molecular weight distribution.

ISSN:0148-6055    

DOI:10.1122/1.549142

出版商:The Society of Rheology    

年代:1969

数据来源: AIP

摘要:

The mechanical properties of a salt‐filled polyurethane elastomer have been investigated at high rates of strain and at several temperatures. Constant strain‐rate tests up to 27 in./in./sec at temperatures from 40 to 160°F have been performed to determine the relaxation modulus in tension and the effects of strain and temperature on this modulus. The effects of time, strain, and temperature have been found to be separable for this highly filled material even after de‐wetting has occurred and the stress‐strain curve becomes highly nonlinear. The relaxation modulus has been evaluated over a time range from10−4to102sec at 70°F.

ISSN:0148-6055    

DOI:10.1122/1.549135

出版商:The Society of Rheology    

年代:1969

数据来源: AIP

摘要:

The steady‐state capillary flow data for several commercial polystyrene melts have been analyzed, and the shear‐dependency of viscosity for these melts has been compared with theoretical results from Pao’s nonlinear hydrodynamic theory. Pao’s theory allows one to calculate the shear‐dependent viscosity in terms of viscoelastic constants, such as retardation times and shear compliances which can be obtained from tensile creep experiments. Using the viscoelastic data obtained in Part II of this series in Pao’s equation, a semiquantitative agreement has been obtained. In most cases, the agreement was within a factor of two in the range where experimental data were available. Introducing a modifying factor common to several commercial polystyrene melts in calculating the retardation spectrum has improved the agreement between experimental data and theoretical results.

ISSN:0148-6055    

DOI:10.1122/1.549143

出版商:The Society of Rheology    

年代:1969

数据来源: AIP

摘要:

Steady flow in the metering section of relatively narrow channel extruders can be regarded as a special case of curvilineal viscometric flow (as defined by Coleman, Markovitz, and Noll). It is shown that under these conditions the behavior of simple fluids can be adequately described from knowledge of a single shear stress function. To specify this function an extended form of the power‐law relationship is used, as it agrees well with viscometric measurements on polymer melts over a range of shear rates. The equations of motion and energy are solved taking into account the effect of transverse flow in the channel and of a superposed steady temperature profile. Results of the numerical computations are presented in terms of dimensionless parameters, and comparison is made with experimental results. The marked effect on non‐Newtonian fluid behavior on extruder output at low back pressures and on the shape of the screw characteristics is emphasized. The importance of temperature effects is measured by the magnitude of the (dimensionless) Brinkman number. Output versus pressure characteristics are calculated for a range of Brinkman numbers, and it is shown that the predicted temperature profiles in the channel approximate experimentally observed profiles. The results provide a rational basis for extruder design and for predicting the effect of geometrical parameters, operating conditions, and melt rheology on extruder performance.

ISSN:0148-6055    

DOI:10.1122/1.549136

出版商:The Society of Rheology    

年代:1969

数据来源: AIP

摘要:

The problem considered is that of steady laminar flow of an incompressible polar fluid between two parallel plates, one of which is in motion relative to the second. It is shown that the effective viscosity, defined as the shear stress applied to the plates times the distance between the plates divided by the relative velocity of the plates, depends upon the distance between the plates. That is to say, if the applied shear stress is held constant, then as the plates are moved closer together their relative velocity will become slower. The velocity distribution in the polar fluid will change accordingly. It is also shown that at the two extremes of closely spaced plates and widely spaced plates the Couette flow of a polar fluid coincides with the Couette flow of Newtonian fluids, but the Newtonian fluids are of different viscosities. Experimental evidence for the increased viscosity of real fluids between narrowly spaced parallel plates is cited.

ISSN:0148-6055    

DOI:10.1122/1.549137

出版商:The Society of Rheology    

年代:1969

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549144

出版商:The Society of Rheology    

年代:1969

数据来源: AIP