Rheological behavior and foam morphology of linear andmodified ETFEs
Masataka Sugimotoa, Eiichi Nishib, Tahashi Katoa, Takashi Satoub, Sathish K.
Sukumarana, Kiyohito Koyamaa
a Yamagata University, Yonezawa 992-8510, Japanb Asahi Glass, Ichihara 290-8566, Japan

Abstract. We studied the modification of rheological behavior and foam morphology of alternating ethylenetetrafluoroethylene copolymer (ETFE). ETFE copolymerized with vinyl compound showed high G’ and G” at low
angular frequencies, while the linear ETFE showed terminal relaxation behavior as well as other linear flexible polymers.
Although linear ETFE indicated the strain rate independent elongational behavior, the modified ETFE showed the strong
deviation of elongational viscosity from linear viscoelastic regime. We will also report the change of the foam
morphology of the modified ETFE.
Keywords: ETFE, fluoropolymer, rheology, dynamic viscoelasticity, elongational viscosity.
PACS: 83.50.Jf

INTRODUCTION
Ethylene-tetrafluoroethylene copolymer (ETFE) is widely used in many fields such as automobile, modernconstruction, airplane, solar battery panel areas due to the high chemical and thermal resistant, flame retardancy,weathering, an electric insulation properties. Therefore ETFE is intensively explored on the mol e cul a r pa r ame ter s , microstructures, crystallization behaviors, flow behaviors under steady shear, flow instabilities. However, ETFE
is one of typical linear polymers and the improvement of the rheological behavior by introducing the long chain
branch has not been reported.
Now more advanced control of rheological behavior of ETFE is required for the wider applications and precise
processings in which ETFE has not be utilized owing to the limited rheological properties so far. In this paper wetried to introduce the long chain branch into ETFE and the shear and elongational flow behaviors are reported.
Furthermore, we will report the batch foaming behaviors of neat ETFE and the modified ETFE.

EXPERIMENTAL
We used conventional ETFE (C88AX, Asahi Glass Co., LTD, Japan) and ETFE copolymerized with divinyl
compound, which is indicated as ETFE-B. ETFE-B of weight percentages of 5, 10 and 30 was blended with ETFE
by twin-screw extruder, indicated by notations of ETFE5, 10, 30, respectively.

RESULTS AND DISCUSSION
ETFE-B synthesized with divinyl compound showed much elastic viscoelastic behavior in low frequency range,
which neat ETFE indicated terminal flow behavior. Within the measured frequency for ETFE-B G’ was always
higher than G”. G’ is parallel to G” at high frequency and the slope of G’ leveled off with decreasing with frequency.
This means an existence of very long time relaxation component. By blending ETFE-B with ETFE G’ of the blends
at low frequency increased with increasing the weight ratio of ETFE-B. This is due to introduction of long relaxation
time component of ETFE-B which dispersed in ETFE. We carried out the elongational viscosity measurement.
Linear ETFE mere showed smooth increase of elongational viscosity. The curves were independent of strain rate andmerged into one curve. The elongational viscosity of ETFE blended with ETFE-B exhibited steep increase at acertain time, depended on the strain rate.
We carried out batch-foaming by using CO2 as a foaming agent. ETFE blended with ETFE-B showed the smaller cell size andhigher cell number density comparing with those of ETFE.