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50
Journal of Science and Technology in the Tropics (2010) 6: 49-52
Digital
Oscilloscope
N2
In order to evaluate the effectiveness of the plasma
jet in modifying the PE surface, hydrophilicity test
was performed. The contact angle of water droplets
at the surface of the PE film was measured using a
rame’-hart Contact Angle Goniometer. This unit
was equipped with standard software to analyze the
drop image for the calculation of surface energy.
The system offered a high level of computer aided
precision in measuring contact angle and therewith
facilitating the calculation of surface energy using
different model equation.
The water droplet contact angles on the surface
of PE films treated at different distances from the
nozzle of the jet and for different exposure times were
measured. Each contact angle presented in this paper
was an average of at least four measurements made
on different positions on the surface of PE.
RESULTS AND DISCUSSION
PC.
DAQ.
Voltage
Probe
Current
Probe
An example of the plasma jet obtained is shown in
Figure 2. A discharge between the centre electrode
and the steel cap containing the orifice is expected to
be produced and the jet is formed due to the flowing
nitrogen stream. The electron temperature of the
plasma near to the orifice is expected to be several
electron-volts. However, the temperature of the ions
and the neutral atoms/molecules is relatively cold and
was measured by using an IR thermometer to be in
the range of 28°C to 30°C. The length of the jet was
found to be dependent on the gas flow rate (Fig. 3).
The flow rate of nitrogen was varied from 1 to 5
litres per minute. To measure the length of the jet,
a scale was placed behind the jet while taking the
Arc
Plasma
Jet
Emission
Spectrometer
Figure 1. Experimental setup of the plasma jet.
Figure
1.
Experimental
setup
of
the
plasma
jet.
High
Frequency
Power
Supply
image of the jet by a digital camera. The lengths were
then determined from the photograph. It is clear that
the length of the jet increases proportionally with the
gas flow rate at the beginning and then levels off after
4 litres per minute (Fig. 3).
Length of visible jet [mm]
Figure 2. A picture of the non-thermal plasma jet.
75
70
65
60
55
1 2 3 4 5
Gas flow rate [l/min]
Figure 3. Dependence of the jet length of APPJ on
the flow rate of nitrogen.
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