摘要:

The steady‐state melt flow behavior covering six decades of shear rate was studied for various types of polyethylene and their blends. Two instruments were used. The Kepe's cone and plate consistometer measures viscosities at low shear rate at the range from10−2to1 sec−1.A gas‐driven capillary viscometer gives high shear data. The shear stress at the capillary wall was calculated by the method proposed by Bagley and the shear rate at the wall was obtained after Robinowitsch. A special effort was made to observe the change in low shear flow behavior of a resin due to an addition of gels, high ends or low ends of molecular weight distribution. Addition of low ends up to 20% does not alter the “shape” of the viscosity shear rate flow curve appreciably. But with an addition of high ends, the “shape” of the flow curve changes considerably. With an addition of gels, the flow curve at low shear rises rapidly as shear rate decreases. An inflection was observed followed by a “tail‐up” at the low shear range.

ISSN:0148-6055    

DOI:10.1122/1.548977

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

Melt flow data, obtained from capillaries having constant length‐to‐diameter ratios, but different diameters, do not lie on a single curve. At constant shear rate the apparent viscosity decreases with capillary diameter. This diameter effect has been interpreted by some investigators as an indication of slippage along the capillary wall. This paper presents data which demonstrate that, if corrections are made for pressure drop in the rheometer barrel, the flow curves coincide. Although it has been recognized that pressure losses in the barrel can have a significant influence on melt index values, it has usually been assumed that they are negligible in high shear measurements. However, if reliable flow curves are to be obtained, the barrel losses cannot be ignored. Furthermore, the value of losses can be used to calculate the shear stress in the barrel and thus extend the range of the measurements.

ISSN:0148-6055    

DOI:10.1122/1.549007

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

The theory of perfect elastic fluids deals with the non‐equilibrium thermodynamics of finite viscoelastic deformation. The thermodynamics of finite elastic strain and of perfect elastic fluids are discussed. It is shown that the stress‐strain relations for perfect elastic fluids may be written in a way which appears formally identical to those in elasticity theory, but the form of this dependence depends on past history.

ISSN:0148-6055    

DOI:10.1122/1.548978

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

A method has been developed for measuring three orthogonal forces in a polymer melt subjected to shear. Data are presented showing the relationship of these forces to shear rate for linear polyethylene. It has been found possible to measure the elastic and viscous forces while varying the shear rate in two different independent manners: (1) by varying the time scale of applying a given magnitude of shear deformation; (2) by varying the magnitude of shear deformation for a given time scale of application. Method number one results in the usual nonlinear relationship between shear stress and shear rate for polymer melts. Method number two results in a linear relationship between shear stress and shear rate thus making it possible to determine a single value of the coefficient of viscosity for any given time scale of application of shear strain. By varying the time scale of strain application, it has been found possible to measure polymer melt viscosities from essentially the zero shear rate viscosity to the disentangled viscosity.

ISSN:0148-6055    

DOI:10.1122/1.548979

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

The steady‐state melt viscosities of both high density and low density polyethylene have been investigated for a series of samples over four decades of shear rate and a range of temperatures from 120°C (150°C for high density samples) to 300°C. In the case of low density polyethylene a broad range of molecular weight distributions was covered. Melt viscosity measurements were made using a capillary extrusion rheometer and a capillary withL/D=66.7for which it was demonstrated that end‐corrections were negligible. Using arbitrary reference temperatures, a superposition‐temperature method was found to be applicable over the entire region of shear rates and of temperatures. A single set of superposition shift factors (for a given reference temperature) was found to be general for all low density polyethylene samples regardless of molecular weight distribution, and a second set was applicable to all of the high density samples. The dependence of the shift factors on temperature was described by a simple exponential, or Arrhenius, equation with activation energies of 11.3 kcal/mole and 6.3 kcal/mole for low density and high density polyethylene, respectively.

ISSN:0148-6055    

DOI:10.1122/1.549006

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

Yield stress master curves are presented for poly(methyl methacrylate), polystyrene, polyvinyl chloride, and polyethylene terephthalate. Tensile yield stress was measured at strain rates varying from 0.003 in./in./min to 300 in./in./min and at temperatures varying from approximately 15°C above the glass transition temperatureT0to at least 100°C belowT0.The resultant yield, or in the brittle temperature range, failure stress, when plotted as a function of logarithm of strain rate, has been shifted laterally to construct a yield stress master curve similar in concept to the well‐known stress relaxation master curve. These master curves cover from 12 to 18 decades of shifted strain rate. The master curve for each material has a characteristic slope which leads, in each case, to a simple equation relating yield stress to strain rate and temperature and is applicable for temperatures fromT0to approximately 100°C belowT0.The temperature‐dependent shift factorsaTof each material were determined for both yield stress and stress relaxation over the temperature range. Comparison of theseaTcurves shows that in both the ductile and brittle temperature ranges of each material, the shape of the yield stress and stress relaxationaTcurves are very similar. However, the absolute magnitude of the change with temperature can be substantially different. Two possible explanations for this difference are offered.

ISSN:0148-6055    

DOI:10.1122/1.549008

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

The equations governing pressure flow and drag flow of the power law fluid in channels of rectangular cross‐section have been solved. Application is made to the calculation of wall effects and die characteristics for screw extrudes. It is shown that the Newtonian wall corrections usually used in extruder calculations can lead to considerable error for markedly non‐Newtonian melts in deep flighted screws.

ISSN:0148-6055    

DOI:10.1122/1.549009

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

The theoretical analysis of mandrel processes has been extended to cases involving viscous materials. An exact solution is obtained for the Newtonian fluid. The results show that a wide range of biaxial stretching patterns can be obtained by controlling the surface friction, input and take‐off velocity and the temperature gradient. Conditions necessary for uniform biaxial stretching are shown.

ISSN:0148-6055    

DOI:10.1122/1.548980

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

The investigation of the torsional creep and recovery behavior of a coordination polymerZn[OP(Ph)(Me)O]2at five temperatures from 100 to 200°C has revealed an unusual rheological behavior. A high temperature aging effect which appears at least partially reversible is observed. Observed creep deformation which is linear in time, followed by a delayed recovery, is explained as a consequence of a void in the retardation spectrum. Temperature reduction is achieved and the temperature shift factors are analyzed in the light of the WLF equation. The measurements were made with a recently developed creep instrument which employs a magnetically levitated rotor and a drag cup motor for precision torque production.

ISSN:0148-6055    

DOI:10.1122/1.549010

出版商:The Society of Rheology    

年代:1965

数据来源: AIP

摘要:

Diseases of the respiratory tract may be related to the altered rheological properties of the respiratory tract mucus and to the altered ciliary shearing capabilities. Flow curves are presented showing that mucus has thixotropic properties and has discrete yield points. Mechanical models of cilia constructed to perform oscillatory motions comparable to thosein vivohave been studied as shearing elements in a modification of the Hoppmann‐Miller Rotational Fluid Flow Generator. A description of those modifications is presented with special attention being given to the design of special cams needed to carry out the proper oscillation of the simulated cilia. Flow trends and particle path lines are described for the mechanical cilia oscillating in and out of phase. Linear velocity of small particles injected into the flow is measured as a function of frequency of oscillation. Finally, some interesting questions are raised pertaining toin vivociliated activity in light of experience gained with the apparatus.

ISSN:0148-6055    

DOI:10.1122/1.549011

出版商:The Society of Rheology    

年代:1965

数据来源: AIP