Proc. XIVth Int. Congr. on Rheology

August 22-27, 2004Seoul, Korea

Edited by:Copyright 2004 – The Korean Society of RheologyLinear and Nonlinear Viscoelastic Properties ofEthylene Ionomer Melts
Mihoko Nishio, Akihiro Nishioka, Masataka Sugimoto, Takashi Taniguchi, Kiyohito Koyama
Department of Polymer Science and Engineering, Yamagata University
4-3-16 Jonan, Yonezawa, JapanABSTRACT
The effects of ionic interaction on linear and nonlinear viscoelastic properties of poly –(ethylene-comethacrylic acid) (EMAA) ionomers were investigated. We have measured zero shear viscosity andsteady shear viscosity of EMAA ionomers. The samples used in this study were partially neutralized byNa and Zn ions, and the neutralization of each samples were changed various. Ionomer neutralized withbinary metal ion (Na and Zn ions) were also measured. The zero shear viscosity is affected hardly
neutralization. In the steady shear, ionomer which neutralized a little caion is fitted by K-BKZ model. For
high neutralization ionomer, K-BKZ model is smaller than in step shear stress relation.

INTRODUCTION
Ionomers are polym ers including a smal l amount of metal ionic salt groups. Above al l, poly(ethylene-co-methacrylic acid)(EMAA) neutra
lized with met al cations are the most wi delyused as ionomers for various industrial applica
tions. The struct ure and mechanical propertiesof ethylene ionomers were extensively investi
gated in both the solid and m elt state. Ionicgroups t end to form ionic aggregates in thehydrophobic polymer matrix. It has been inves
tigated that the microphase separation of ionicaggregates and t he hydrocarbon matrix takeplace according to the neutralization degree by the dielectric and dynamic mechanical relax
ation studies. It is known that ionic aggregate
s were formed more than the neutralization degree of 35% in EMAA- Na ionom er and t hatof 80% in EMAA-Zn. It has been reported that physi cal properties of ionomers depend on
the kind of added metal (e.g., alkaline and transition metal) due to the difference in their io
nic strength and the number of carboxyl grou

ps associated with one metal cation. Since themetal cation dependent characteri stics of iono
mers are essenti al in mechanical and rheologic
al properties , under solid and melt state of ethylene ionomers have been studied. To clarify the role s of ionic bondings and its aggregat
es in ionomers under melts are very importantresearch subj ect. In t his study, linear and nonlinear viscoelastic properties of ethylene iono
mer.

Experimental
We have measured m elt viscos ity of ethylenem ethacrylic acid (EMAA) ionomers by meansof steady flow and step shear. The base poly
mer is EMAA which methac rylic contents 5.4
mol%, the samples used in this study were neutralized by Na salts and metal cation content
s were changed various.

August 22-27, 2004
Seoul, Korea

Proc. XIVth Int. Congr. on Rheol
ogy
Edited by:Copyright 2004 – The Korean Society of Rheology

Results and Discussion

REFERENCES
1. Bernstein B.,E.A.Kearsly, L.J.Zapas, Trans.S
co.Rheol.,7,391-410(1963)
2.Papanastasiou A.C., L.E.Scriven, C.W.Maco
sko,J.Rheol.,27,387-410(1983)

Zero shear viscosity(Pas)105104
Na ionomer
Zn ionomer

01020 30 40 50 60
Neutralization(%)

70

Fig.1 The dependence of η0 on theneutralization level on η0 for Zn and Natype ionomer.
)γ106・γ(s-1)(a) EMAA-28%Na
140oC

0.5
0.1
0.05
0.01

510η s (Pa s)

Figure 2 (a) and (b) show the start up ofsteady shear viscosities for EMAA-28%Na andEMAA-54%Na, respectively. And these results
fitted by K-BKZ Model[1][2]with damping
parameter obtained from step shear were shown.
For EMAA-28%Na, the experimental values
agreed well with the prediction from theparameter. It is, however, quite unexpected that
the K-BKZ calculation under predicted theexperimental data in EMAA-54%Na. The bestfitted parameter for EMAA-54%Na from thetransient shear viscosity was more large value. It
should be noted that larger damping parameterrequired in the start-up of shear rather than instep-shear stress relation in EMAA-54%Na. Thismeans that the characteristics of zinc-ionicaggregate in two types of measurements arecompletely different.

106103104

K-BKZ Calc.

3

10-1

0

10

10

1

102t(s)

103

4

10

10

6

10

α=13.7

E/MAA-54%Na(b) 140
EMAA-54%NaC140oCo5ηs (Pa s)

Weperformeddynamic
shear
experiments under the linear region. the dynamic
shear properties revealed that the time-material
superposition was applicable to blend ionomers
from 140oC to 200oC. The value of η0 for Na
increased with increasing neutralization degree,which was found for time-material superposition.
The other hand, for Zn ionomers, until
neutralization of 40% similar tendency wereoccurred phenomena, however the viscosities
unexpectedly increased above 40%.

10710.

γ (s-1)

4

10

0.5
0.1
0.05
K-BKZ Calc.

310-1
101001102t(s)10103Fig.2 Tran sient shear viscosity under constant shear rate con ditions f or EMA
A-28%Na(a) and EMAA-54%Na at 140 oC. The solid line means calculation resul
ts of BK Z model (PSM type) with the dumping paramet er listed in each figures.

104