2C11
Effect of Viscosity Ratio on the Polymer/Polymer Interfacial Slip
○Ryohei Komuro, Sathish K. Sukumaran*, Masataka Sugimoto, Kiyohito Koyama
Graduate School of Science and Engineering, Yamagata University

ABSTRACT: We investigated the effect of themolecular weight of individual layer andtemperature on the polymer/polymer interfacialslip. As seen from this study, it is found that thepolymer/polymer interfacial slip does not sensitive
to the molecular weight, the polymer/polymer
interfacial slippage has similar temperaturedependence even when the concentric core-sheathsamples has different viscosity ratio of individuallayer.
1.

Introduction
Any polymeric products were made using

varioustypesofpolymericmaterials(e.g.

molecular structure, molecular weight, molecularweight distribution etc…) under various condition(e.g. temperature, pressure, flow rate, etc…). These
factors influence the viscoelastic properties ofpolymeric material. As a result, the flow behavior
is affected by these factors. In case of multi-layer
polymer processing, the multi-layer flow behavior
and the interfacial properties would be affected bythese factors as well, because two or more materials

core-sheathsampleshasdifferent

shear-rate

dependent viscosities. This method is an adaptationof the Mooney method [3] used to measure the wall
slip velocity.
In this study, we investigated the effect of themolecularweightofindividual

layerandtemperature on the polymer/polymer interfacial slip
using the modified Mooney method [2].
2.

Experiments
The experimental samples were chosen three

types of PP (PP1-3) and three types of PS (PS1-3)
with the different molecular weights. PPs werekindlysuppliedbySumitomo

ChemicalCorporation and Japan Polypropylene Corporation.
PSs were kindly supplied by PS Japan Corporation.
The interfacial slip velocity was evaluated using
capillary dies of three different diameters D=1.0,
1.5 and 2.0 mm.

are extruded through a single die.
In addition, in case of immiscible polymersystems,

theexistenceofslippage

at

thepolymer/polymer interface might be expected,
because the different polymer chains are weakly
entangled leading to poor interfacial adhesion.
Actually, some scientists [1] pointed out theexistence of polymer/polymer interfacial slip inmulti-layer flow. However, the determination of thepolymer/polymer

interfacial

slipvelocity

incoextrusion is not straightforward when two or
more polymers with different shear-rate dependent
viscosities. Accordingly, nobody knows that theeffect of the molecular weight of individual layer
and temperature on the polymer/polymer interfacialslip in coextrusion.
Recently, Komuro et al. [2] proposed a novel
method (the modified Mooney method) to estimate
the slip velocity at a polymer/polymer interface in
two-phase coaxial flow even when the concentricFig. 1 (a) Cross section of PP coated with PS sample and(b) the boundary condition of flow velocity distribution
in two-phase coaxial flow.

Fig. 1 shows the schematic illustration of thecross section of PP coated with PS sample and theboundary condition of flow velocity distribution in
two-phase coaxial flow. The polymer/polymer
interfacial slip velocity was evaluated using eq. (1).
The detail of experimental procedure was written inref. [2].

⎡R 3 σ i ⎛ dV ⎞R3 σ w⎛ dV ⎞ ⎤QPP/PS = π ⎢ Ri2Vs − i + i3 ∫ σ 2 ⎜ − PP ⎟dσ + 3 ∫ σ 2 ⎜ − PS ⎟ dσ ⎥.
σi 0σ w σi
⎝ dr ⎠⎝ dr ⎠ ⎦⎣(1)

Fig. 3 Vs-i as function of σi for PP1/PS3 at 230oC, 208oC,and 187oC.

PP/PS and PP3/PS3, it is found that thepolymer/polymer interfacial slip does not sensitive
to the molecular weight even if the concentricFig. 2 (a) |η*| and ηs of PP1-3 and PS3 at 230oC. and (b)Vs-i as function of σi for PP1-3/PS3 at 230oC.
3.

Effect of the molecular weight on thepolymer/polymer interfacial slip:
PP1-3/PS3. The Vs-i exhibits the power-law
dependence on σi (Vs-i =Kσim), and the power-law
dependence falls displays two distinct regimes withthe power-law exponent at an critical interfacial
shear stress (≈2×104Pa). From the Fig. 2(b), theofinterfacial

slip

transition

atapproximately 2×104Pa, the power-law exponent at
the region A and B, the actual value of Vs-i forseveral σi were almost same for PP1-3/PS3. These
resultssuggested

thattheEffectoftemperatureon

thepolymer/polymer interfacial slip:
Fig. 3 shows Vs-i as function of σi for PP1/PS3 at
230 C, 208oC, and 187oC.. As seen from these results,oFig. 2(b) shows the log Vs-i versus log σi forexistenceover a range of shear rates.
3.2

Results and discussions

3.1

core-sheath samples has almost identical viscosities

polymer/polymer

interfacial slip does not sensitive to the molecularweight.
In addition, the polymer/polymer interfacialoslip velocity at 230 C using PP and PS with thequite similar viscoelastic properties over a range ofshear rates were also shown in Fig. 2(b) [2]. Here,
we focused on the PP/PS [2] and the PP3/PS3.
Alghough the both of the PP/PS and the PP3/PS3
are the almost identical viscosities pair over a rangeof shear rates ((ηPP ≈ ηPS) > (ηPP3 ≈ ηPS3)), themoleculer weight of PP/PS are higher than
PP3/PS3. From the comparison between the Vs-i for

it is found that the polymer/polymer interfacialslippage has similar temperature dependence evenwhen the concentric core-sheath samples has
different viscosity ratio of individual layer.
4.

Summary[1] The polymer/polymer interfacial slip does notsensitive to the molecular weight.
[2] The polymer/polymer interfacial slippage has
similar temperature dependence even when theconcentric core-sheath samples has different
viscosity ratio of individual layer.
Acknowledgment:
The authors gratefully acknowledge financial support
from the Japan Society for Promotion of Science (JSPS)
through Kakenhi (24350114) and the Dissemination ofTenure Tracking System Program of the Ministry ofEducation, Culture, Sports, Science and Technology -Japan.
References:[1] e.g. Lee PC, Park HE, Morse DC, Macosko CW, J.
Rheol., 53:893-915, 2009 etc…
[2] Komuro R, Sukumaran SK, Sugimoto M, Koyama K,
Slip at the Interface between Immiscible Polymer Melts
I: Method to Measure Slip, under review, 2013[3] Mooney M, J. Rheol., 2:210-222 1931.