2018 International Symposium on Dry Process

P-115

Surface Modification of Polytetrafluoroethylene by Line
Shaped Ar/Ethanol Atmospheric Pressure Plasma Jet
H. Yajima1, I. Serizawa1, H. Furuta2, and A. Hatta2
ORC Manufacturing Co. Ltd., 4896 Tamagawa, Chino, Nagano 391-0011, Japan
Kochi University of Technology, 185 Miyanokuchi, Tosayamada, Kami, Kochi 782-8502, Japan
Email: h-yajima@orc.co.jp
12

By using line shaped atmospheric pressure plasma jet (APPJ) of Ar with ethanol vapor, thewettability of polytetrafluoroethylene (PTFE) surface was improved. After plasma treatment for 10
minutes, hydrophilic surface of 42 water contact angle was achieved while the original surface
showed 113. It was found that Hydrogen molecules were produced from ethanol in the APPJ.

1Introduction

For
varietyof
industrial
applicationofpolytetrafluoroethylene (PTFE), it is required toimprove the surface property of poor adhesion withother materials. Plasma surface treatments have been
expected to modify the PTFE surface and somesuccessful results have been reported. Atmosphericpressure plasma techniques have many advantages fortreatment of polymer surface; no usage of vacuum
system, simple configuration of apparatus, high density
plasma for rapid treatment, small environmental impact,and so on.
We previously reported surface modification of PTFE
by atmospheric pressure plasma using mixture gas of
Ar and ethanol vapor with parallel plate electrodes
configuration [1]. Due to the configuration, however,
the treatment is limited for thin sheet of PTFE set
between the electrodes for dielectric barrier discharge(DBD). For treatment of thick material with variety ofshapes, irradiation to atmospheric pressure plasma jet(APPJ) will be effective. For such the surface treatment,
we have been developing a line shaped DBD-APPJ
device which can eject line shaped plasma plumeinstead of the pencil type APPJ [2].
In this study, we examined surface modification ofPTFE by the line shaped Ar/ethanol DBD-APPJ. The
hydrophilicity of treated PTFE was evaluated and thechemical component in gas jet was analyzed using
quadrupole mass spectroscopy (QMS).

2

outsides of the glass plates, and a 25 kHz sinusoidal
wave voltage at 10kVp-p was applied to the electrodes.
The sample of PTFE sheet was located at the exit ofAPPJ. Before plasma treatment, the samples werewashed in an ultrasonic cleaning instrument by using
acetone for 5 min., and then, rinsed in ethanol andultrapure water for each 5 min. Treated PTFE samples
were characterized by the static water contact angle 30
seconds after dropping distilled water. The volume ofwater drop was around 1 PL.
Figure 2 shows experimental setup of QMS
measurements. The tip of glass capillary was locatedjust below 1 mm flow the exit of APPJ apparatus.

Fig. 1 Experimental setup of PTFE surface
modification by APPJ.

Experimental setup

Figure 1 shows experimental setup of PTFE surface
modification and APPJ configuration. Ar gas wasbubbled in ethanol in a bottle for supplying the ethanol
vaper and the mixture gas was fed into the discharge
gap. Ar gas was supplied at a flow rate of 500 sccm andthe mixing ratio of ethanol vapor to Ar gas was 5.7 %by controlling the ethanol temperature at 20 C. A DBD
was operated in a small gap between a pair of glass
plates with a pair of electrodes stuck on both theFig. 2 Experimental setup of QMS for APPJ.

3Results and Discussion

Figure 3 shows water drop images on PTFE untreatedand treated with Ar or Ar/ethanol APPJ for 10 minutes277

at 1 mm irradiation distance. By using Ar/ethanol APPJ,
hydrophilic surface of 42 water contact angle wasachieved while the original surface showed 113. As it
has been reported that Ar plasma was effective forhydrophilic PTFE [3], the Ar APPJ treated PTFE also
showed slightly decreased water contact angle 91.
Figure 4 shows H2+ (m/z = 2) current of QMS
measurements at 1 mm distance from the APPJ exit
with Ar or Ar/ethanol with plasma on and off. In thecase of Ar/ethanol APPJ, hydrogen molecules weregenerated from decomposition of ethanol (C2H5OH).
The production of hydrogen molecules implies possible
existence of hydrogen radicals in the plasma jet. It canbe assumed that C-F bonds of PTFE surface wasdecreased by attack of hydrogen radicals with resulting
in the highly improved wettability [4].
UntreatedT = 113

ArT = 91

Fig. 5 Treatment time dependency ofstatic water contact angle on PTFE
treated with Ar/ethanol APPJ .

Ar/ethanol (5.7%)
T = 42Fig. 3 Water drop images on PTFE untreated andtreated with Ar or Ar/ethanol APPJ for 10minutes at 1 mm irradiation distance.
Fig. 6 Irradiation distance dependency ofstatic water contact angle on PTFE
treated with Ar/ethanol APPJ.

4Fig. 4 H2+ (m/z = 2) current of mass spectra at 1mm irradiation distance generated by Ar orAr/ethanol APPJ.

Figure 5 shows dependency on the treatment time of thestatic water contact angle of treated PTFE surface withAr/ethanol APPJ at 1 mm irradiation distance. Thedecrease of contact angle was saturated at around 42
in 10 minutes.
Figure 6 shows dependency of the static water contact
angle on the irradiation distance from the exit of APPJ
with Ar/ethanol for 10 minutes. It was confirmed thatthe irradiation was effective to improve the wettability
below 5 mm distance.
The resulting improvement of wettability was not
sufficient for a practical use, it is necessary to optimize
the operation conditions of APPJ.

278Conclusion

The hydrophilicity of PTFE treated by the line shaped
DBD-APPJ device using Ar/ethanol gas was examined.
After plasma treatment for 10 minutes, hydrophilic
surface of 42 water contact angle was achieved while
the original surface showed 113. It can be assumed thatC-F bonds of PTFE decreased by attack of hydrogenradicals generated from ethanol with resulting in the
improved wettability.

References[1] H. Yajima, T. Hayakawa, I. Serizawa, K. Ogawa, H.
Furuta and A. Hatta, in Proc. The 65th JSAP Spring
Meeting, Tokyo, Japan, 2018, 07-126.
[2] H. Yajima, I. Serizawa, H. Furuta and A. Hatta, in
Proc. Plasma Conf. 2017, Hyogo, Japan, 2017,21P-119.
[3] X.-J. Shao, G.-J. Zhang, J.-Y. Zhan and G.-M. Xu,IEEE Trans. Plasma Sci. vol. 39, no. 11, pp. 30953102, 2011.
[4] N. Inagaki, S. Tasaka, K. Narushima and K.
Teranishi, J. Appl. Polym. Sci. vol. 83, pp. 340-348,2002.