Melt Rheology of Sodium and Zinc Ethylene Ionomer
Kiyohito Koyama, Mihoko Nishio, Akihiro Nishioka, Tatsuhiro Takahashi andDepartment of Polymer Science and Engineering,
Yamagata University
4-3-16, Jonan,Yonezawa 992-8510, JapanAbstract
The ionic bonding is one of parameters to control melt rheology. Ethylene
poly-(ethyleneco-methacrylic acid)(5.4mol% of MAA, EMAA) which is partially neutralizezinc. There have been several reports about melt rheological properties of sodiu
However, few reports have been published to examine the melt rheological propertie
spite of their some industrial commercial applications.
Rheological characterizations were carried out under shear in terms of li
oscillatory shear. The ionomer blends here have 60% of neutralization and variou
Time-material superposition was applicable among sodium, zinc ionomers, and their iviscosity as a function of blend composition unexpectedly showed that the zero she
80% is almost constant with that of sodium ionomer. However, ionomer blends surpri
damping than each ionomer, depending on the composition. The unexpected zero shear
from acid-cation exchange mechanism, which is observed only in sodium ionomers, not

1. Introduction
Poly(ethyleneco-methacrylic acid) (EMAA) partially neutraliions such as sodium or zinc is one of the most widely used
and mechanical properties in the solid state of these eth1)
been extensively investigated.
Ionic cross-links and the aggregatiogroups impart a dramatic increase in mechanical propertie
properties are essential for sodium and zinc of EMAA tovariety of industrial applications viscoelastic properties oionomer melts have also been studied to clarify the role o2-4)
5)state.
Especially, Vanhoorne andstudiedRegisterthe effect of theof unneutralized acid groups on the melt rheology of partialionomers. By removing the protons by esterification of thhave found that the role of the protons in sodium ionomers5)
in zinc ionomers.
In this paper, in order to get deeper insight into therheology, we have studied dynamic shear properties for blend
and zinc ionomers as a function of the blend ratio. In thblends, the zero shear viscosity as a function of composit
additively rule, while a strong negative deviation from th
was observed in the latter blends. A possible explanation ogiven.
2.

Experimental

Poly(ethyleneco-methacrylic acid)(EMAA,Mw=94,500 Mn=19,200)
a methacrylic acid content of 5.4mol% was used. Ethylene ba

EMAA partially neutralized by zinc or sodium ion, that i(EMAA-59Zn, EMAA-54Na). The samples were mixtures of theseoionomers. The blends were prepared by double-screw
C. Theknead
blend ratio of two cation ionomers were written in Tabl
abbreviations are designated as EMAA-Zn(x)/Na(y), where x
blend ratios of two cations. All of these samples wereoC for these
Mitsui-DuPont Polychemicals. The melting temperature
waso
C for ovenat leastsamples. All samples were treated with vacuum
at 80onweek to eliminate water before measurements.
Dynamic shear measurements were conducted using a rotati(Rheometrics, ARES) under nitrogen atmosphere. These expo
conducted in the range from 0.01 to 100 oC
rad/sand 200
betweenC, which140
are substantibially above their melting point.
3.

Results and Discussion

Oscillatory shear experiments for samples shown in Tstrain (less than Hencky strain 0.04) were performed. Storloss modulus G" were obtained as a function ofw angularin the fr
range from 0.01 to 100 (rad/s). Firstly it was comfirmed thasuperposition principle is applicable for EMAA-Zn(33)/Na(67in measured conditions. Secondly the resulting master curvoEMAA-Zn(33)/Na(67) at temperature
C wereof 140
horizontally shiftedoC. 140
It was shown in Figure 1 that the successfu
master curve at3)
(i.e. Super master) ofcurve
G’ and G’’ for EMAA-Zn(30)/Na(67) wasat the G’ and G’’ of EMAA as the refference. For the other3)
time-material
superposition principle was also applicable.
construction of super master curve can be interpreted as thmust have the same shape of relaxation spectrum with differ3)
expressed by material shift. Thisfactorsshift factor value is importa
it is well satisfied following relation to hthezero-shear vo.

h o(EMAA-X) =aT* ho (EMAA).

(1)

HereaT* is the time-material shift factor for EMAA-X reland ho(EMAA) andho(EMAA-X) are the zero-shear viscosity of E
EMAA-X, respectively. Figure 2, it shows foraT asvariousa function
blendsoEMAA-59Zn content These blends are miscible, but a large nfrom the linear blending rule was observed. In the case oacid-cation exchange mechanism is effective because COOH gr
aggregates, resulting in lower viscosity. In EMAA-59Zn, onacid-cation exchange does not occur because no acid groupaggregates, and the viscosity is relatively high. When EMAA

59Zn were blended, it can be explained by the idea that socoexisted in the same ion6)whereaggregates,
the acid-cation exchange is oTable 1

The samples for binary blends of EMAA-Na and EMAA-Zn
Zn : Naion ratio(mol)Sampleabbreviation

EMAA-Zn : EMAA-Na
weight ratio(wt%)

EMAA-Na(100)

0:10 : 100

EMAA-Zn(20)/Na(80)

1:4

31.4 : 68.6

EMAA-Zn(33)/Na(67)1:2

47.8 : 52.2

EMAA-Zn(50)/Na(50)1:1

64.7 : 35.3

EMAA-Zn(67)/Na(33)

2:1

78.6 : 21.4

EMAA-Zn(80)/Na(20)4:1

88.0 : 12.0

EMAA-Zn(95)/Na(5)95 : 597.2 : 2.8

EMAA-Zn (100)1:0

100 : 0104

106

Material shift factor, aG',G''(Pa)10TSuper-Master CurveRef) EMAA 140℃

5104103102103

101
100 -21010210-1010110210w(rad/s)

10310410

5020

4060
EMAA-59Zn(wt%)

80

100Fig.1 Time-material superposition ofG’(squareFigure
2 Time-material shift fasymbols) and G"(circle symbols) fromatthe
140℃masteras the reference) as
curves of EMAA(closed symbols) and thoseofcompositionin the blend of EMA
EMAA-Zn(33)/EMAA-Na(67) (open symbols).
and EMAA-59Zn.
The reference is the master curves of EMAA℃
at 1404.

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