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Pressure variation and flow birefringence of polymer melts in flows through straight ducts with approaching channel

  • Teikichi Ami

Abstract

In 1962, the author and Aoyama put forward a paper on the interrelation between Barus effect and tube length correction term coefficient (1). Here the cause of the die swell was attributed to the mechanical energy. The principal defect of the paper is that the effect was conclusively directed to the shear strain of the polymer melt flowing through a nozzle. In 1966, at the International Symposium on Macromolecular Chemistry held in Kyoto, a paper on the revision of the forgoing concept was presented where the cause of the die swell was attributed mainly to tensile strains of the flowing melt from a new experimental result on the die exit pressure (2, 3). In 1967, at the 5th International Congress on Rheology in Kyoto, the author presented further experimental results on the interrelations between die swell and die exit pressure (4, 5). The present paper deals with the experimental results so-far obtained in his laboratory within the last 4 years on the elastic responses of melts in steady and in pulsatile flow conditions. For the clarification of the responses, experiments were carried out by the following three different resorts:
  1. (1)

    Investigations on the interrelation between the pressure distribution along the length of circular duct with a contraction portion and the Barus Effect Index ᾱ given by the ratio of the cross-sectional area of the extrudate to that of the nozzle.

     
  2. (2)

    Measurements of the pressure propagation along the length of flow direction in the pulsatile flow through a circular duct with an approaching channel.

     
  3. (3)

    Measurements on the flow birefringence of polymer melt passing through a slit duct, and the application of photoelasticity analysis for the elastic solid to the flow of the liquid.

     

Notation

Dnoz

nozzle diameter L

Dres

reservoir diameter L

H

slit clearance L

Lnoz

nozzle length L

P

pressure ML −1 T −2

Pent

driving pressure calculated by ML −1 T −2 linear extrapolation of the pressure gradient curve in the reservoir to the nozzle inlet plane

ΔPent

pressure drop at the nozzle inlet ML −1 T −2

ΔPent

residual pressure at the nozzle ML −1 T −2 exit

Q

volumetric flow rate L 3 T −1

Rent

nozzle radius L

T

slit width L

z

coordinate parallel to the axis of L nozzle or slit in flow direction

Barus Effect Index dimensionless

y h/2

apparent shear rate at the slit T −1 wall

γ ̇′ R-noz

apparent shear rate at the wall T −1 of nozzle

θ

temperature (degree in Centi- θ grade)

v

nozzle length correction term dimensionless coefficient

vent

coefficient of the entrance cor- dimensionless rection term

vexit

coefficient of the exit correction dimensionless term

ξ

pressure gradient ML −2 T −2

ξη

pressure gradient due to viscos- ML −2 T −2 ity resistance

ξnoz

duct contraction ratio at the dimensionless nozzle entrance

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References

  1. 1).
    Aral, T. and H. Aoyama, Trans. Soc. Rheology 7, 333 (1963).ADSCrossRefGoogle Scholar
  2. 2).
    Aral, T., I. Suzuki, and N. Akino, “Pressure Determinations along Die Axis in a Round Tube Extrusion”, paper presented at the International Symposium on Macromolecular Chemistry, Sept. 28, 1966, Kyoto.Google Scholar
  3. 3).
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Copyright information

© Springer-Verlag Berlin Heidelberg 1975

Authors and Affiliations

  • Teikichi Ami
    • 1
    • 2
  1. 1.Division of Mechanical EngineeringKeio UniversityHiyoshi-cho, Yokohama 223Japan
  2. 2.Bunkyo-Ku, Tokyo 113Japan

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