摘要:

In this article, the rectilinear pipe flow of a polymeric liquid under a time‐dependent pressure drop is considered. The fluctuating component of the pressure drop is assumed to be of small amplitude and can adequately be represented by a weakly stationary stochastic process. Perturbation solutions are developed for two integral constitutive equations; both have strain‐dependent memory kernels. The first is the recently proposed nonaffine network model and the second is a simplified version of the B‐KBZ constitutive equation. It is shown that both models predict a positive flow rate enhancement. This flow enhancement is a decreasing function of the frequency of the fluctuating pressure drop when the latter is represented by a sinusoidal function of time. Based on the limited data published by Barnes, Townsend, and Walters, it is concluded that both models considered here cannot describe the frequency dependence of the flow enhancement. In this regard, it would appear that an integral model with a strain‐rate dependence memory kernel is best suited for this flow field despite a number of theoretical defects that can be leveled against it.

ISSN:0148-6055    

DOI:10.1122/1.549618

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

摘要:

If one monitors the performance of an adhesive with a 180° peel test, then the flow‐field to a good approximation is uniaxial extension at a decreasing rate. In our work a polyester adhesive was subjected to careful rheological characterization, including measurement of its extensional flow response. The response to extensional flow was used, in turn, to predict peel force using the early concepts of Gent and Petrich with excellent results. A form of the BKZ constitutive equation was also used to predict the stretching response and, in turn, the peel force. Again, very good agreement with experimental peel‐force results was obtained. The applications of extensional rheometry to the selection of adhesives are discussed.

ISSN:0148-6055    

DOI:10.1122/1.549619

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

摘要:

Scaling in terms of temperature, composition, and molecular weight variables has practical and fundamental significance. The hydrodynamics of hard sphere systems suggest the scaling of the dimensionless ratioηsp/(c[η])in terms of a concentration parameterγ(M,T)=1/[η].Solutions of flexible chains indicate the appropriateness of this equation at θ and sub θ conditions, but otherwise a molecular weight dependence of γ differing from that of[η]−1.It is possible however to define a corresponding states principle through an empirical relation between γ andM.In this case1/γ∝kH[η],withkHthe Huggins parameter. This scheme extends in some cases up to the melt. One of us (L.A.U.) has previously considered melt viscosities of low and high molecular weight systems in terms of free volume concepts, combined with theoretical liquid state results, and withTgscaling the temperature. An extension to solutions yields an explicit viscosity‐concentration‐temperature function. Gratifying agreement with experiment can be seen. Structural changes, generated by temperature, concentration, and pressure changes, are reflected in the scaling parameters.

ISSN:0148-6055    

DOI:10.1122/1.549646

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549647

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549620

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549621

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549615

出版商:The Society of Rheology    

年代:1981

数据来源: AIP

ISSN:0148-6055    

DOI:10.1122/1.549654

出版商:The Society of Rheology    

年代:1981

数据来源: AIP