Photon Factory Activity Report 2016 #34 (2017)

BL-6A/2015G620

Growth of Microvoids in Fluorine Elastomer Composites during Stretching
Kenta Kubo, Shinya Maruta, and Masatoshi Shioya*
Tokyo Institute of Technology, 2-12-1-S8-34 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
1 Introduction
The fluorine elastomers are used for coatings, O-ringsand valves due to their excellent thermal and chemical
resistance. However, their high chargeability causes dust
deposit and their mechanical strength is low. Formodifying their properties, attempts have been made todisperse conductive and high strength fillers into fluorine
elastomers. This study compares the influences of carbon
nanotubes (CNTs) and graphene oxide nanoribbons(GONRs) on the mechanical properties and the growth of
microvoids during stretching for the fluorine elastomer
composites containing these fillers. [1]was 2 m and the scattering intensity was measured with
Pilatus 3. The tensile tests and the wear tests were
performed on the elastomer composites.

2 Experimental
A copolymer of tetrafluoroethylene with perfluorovinylether (FFKM, Daikin Industries, Ltd.) was used for thematrix elastomer. Multi-walled carbon nanotubes(MWCNTs, Showa Denko K.K., VGCF-H), withdiameters of 150 nm and lengths of 10–20 μm, were usedfor the fillers and the parent MWCNTs used for
producing the GONRs via the unzipping method. [2]
The FFKM was swollen with a solvent, added with theCNTs or GONRs and mixed using a planetary centrifugal
mixer. After the solvent was evaporated, the mixture waspressed into films 500 μm thick using a hot press. During
the hot pressing, Si3N4 and urea were placed around thefilms for producing crosslinking by the formation oftriazine rings.
The
small-angle
X-ray
scattering(SAXS)
measurements during stretching of the elastomer
composites were performed at BL-6A in PF. The X-ray
wavelength was 0.15 nm, the sample-to-detector distance3 Results and Discussion
Fig.1 shows the tensile modulus, the tensile strength,
the tensile strain at break and the wear resistance for theelastomer composites relative to these values for theelastomer without containing fillers where the wear
resistance is defined as the inverse of the wear rate. The
elastomer without containing fillers had the tensile
modulus of 1.1 MPa, the tensile strength of 3.3 MPa, thetensile strain at break of 2.1 and the wear rates of 7.6×
-11-1
10 Pa . As compared with CNTs, GONRs more
effectively increase the tensile strength and the wear
resistance without causing larger increase in the tensile
modulus.
In Fig.2, the integrated intensity of SAXS is plottedagainst the tensile strain for the elastomer composites.
The integration was carried out by weighting the intensity
at individual pixels with 2π|s| where s is the separation,measured perpendicularly to the stretching direction,
between each pixel and the center beam position. This
integrated intensity is proportional to the total volume of
the microvoids formed at the filler-matrix interfaces. This
figure shows that the growth of microvoids during
stretching is markedly suppressed by dispersing GONRs
in place of CNTs. This result can be attributed to thelarger surface area and the larger amount of functionalgroups for the GONRs as compared with the CNTs.
In some application fields of fluorine elastomers, it isdesired to increase mechanical strength withoutFig. 1: Comparison of tensile and wear properties offluorine elastomer composites containing 1 wt% ofCNTs and GONRs shown by relative values.

Fig. 2: Integrated intensity of SAXS versus tensile
strain for fluorine elastomer composites containing
CNTs and GONRs by the weight fractions shown inthe figure.

Photon Factory Activity Report 2016 #34 (2017)

increasing the tensile modulus and the GONR-dispersion
is more suitable than the CNT-dispersion for suchapplications.
Acknowledgement
The authors are indebted to Profs. N. Igarashi, N. Shimizu
and T. Mori at PF for their experimental support.
References[1] K. Kubo, S. Maruta, M. Shioya, T. Noguchi, Fiber
preprints, Japan, 72, No. 1, 1H09 (2017).
[2] D. V. Kosynkin, et al., Nature, 458, 872 (2009).
* shioya.m.aa@m.titech.ac.jp