Application of atmospheric pressure plasma for comfort properties and imparting functional properties to PP and PET fabrics
By
Pooja M. Shah,
Iceland
Guide Name :
Dr. H. D. Joshi
When
a sufficiently large voltage is applied across a gap containing a gas or a
gaseous mixture, it will break down and conduct electricity. The electrically
neutral atoms or molecules of the gas split into negatively charged electrons
and positively charged ions. The nature of the break down and the voltage at
which this occurs varies with the gaseous species, gas pressure, gas flow rate,
nature of the materials, separation distance of the electrodes, voltage supply
and electrical circuitry. The resulting ionized gas is often called a discharge
or plasma. Plasma used in textiles processing vary considerably but are usually
only partially ionized gases containing electrons, ions and neutral atoms and
or molecules. The inter-actions of the electrically charged particles with each
other, with the neutral gas and with contact surfaces produce the unique
physical and chemical properties of the plasma environment. The environment is
distinct from that found in solids, liquids or gases; hence plasmas are
sometimes called the fourth state of matter. A gas becomes plasma when the
kinetic energy of the gas particles rises to equal the ionization energy of the
gas. When this level is reached collisions of the gas particles cause a rapid
cascading ionization resulting in plasma. When the neutral molecules of a gas
are energized e.g. by exposing to high electric field, to a point when some
electrons become free and the gas turns into a mixture of electrons, ionized
atoms and molecules, photons and residual neutral species. In this state it
behaves as a chemically active species and there is likelihood of surface
interaction with organic substrates.
Atmospheric
pressure plasma (APP) treatment of a textile surface can be employed to impart functional properties to the textile surface.
Plasma treatment with non-polymerizing gases results
in better wettability, hydrophilicity and adhesion. Some of the Polypropylene
(4 varieties) and Polyester (Polyethylene
terephthalate – 4 varieties) were treated with air, oxygen and
helium – APP. The plasma treated fabrics were observed under the SEM to gauge the effect
of plasma treatment. It was found that oxygen-APP did not show significant
surface modifications. Hence all
the fabrics were given air and helium – APP treatment. This initial plasma treatment was carried out at WRA
on small samples (20 cm x 15 cm). After the Continuous
Plasma Treatment machine was installed at MANTRA, 2 varieties each of PP and
PET were given air-APP treatment to continuous length of fabric (10m). The time
duration of plasma treatment was varied
(5 min, 10 min and 15 min).
Maximum
effective plasma treatment was observed for continuous air-APP for 15 min (SEM
images).
The
air APP and helium-APP treated samples were tested for certain properties to
evaluate the effect of plasma treatment. These properties indicate the changes
in surface properties such as wettability, hydrophilicity, adhesion. APP
treatment affects not only the mechanical properties but also the air
permeability, thermal properties and water vapor permeability of PP and PET
fabrics.
The
contact angle values of PP and PET fabrics decreased after plasma treatment
while the capillary rise (LAC, Liquid absorption) also increased. This is an
indicator of increased hydrophilicity of PP and PET fabrics. There is a slight
decrease in air permeability of the APP treated samples which means that plasma
treated fabrics have poorer air permeability as compared to untreated
The
atmospheric pressure plasma treatment (air) given to polypropylene and
polyester fabrics has resulted in changes in surface morphology which has also
affected, some comfort related fabric properties. The changes in liquid
absorption and transfer properties (increased liquid absorption) will
definitely enhance comfort properties. Continuous Air APP treatment at 3-5 kV
for 15 mins gives optimum results with respect to liquid transfer properties.
The decreased air permeability of plasma treated fabrics and thermal insulation clo-values indicate
that the plasma treated fabrics have good insulation properties. Air plasma
treatment reduces the contact angle which also gives improves wettability of
the treated fabrics.
Printing
properties of APP treated fabrics were studied and it was found that plasma treatment
improves the uptake of colour of printed fabrics. The uptake of colour in the
dyeing process is not significantly affected by plasma treatment. Visual
observation and comparison of the printed shades (plasma treated and untreated)
shows the significant difference in uptake of colour. This is supported by K/S
data.
Cost
economic study of plasma treatment process also shows its viability for
industrial application i.e. from initial investment, operational costs are at
par with other textile processes. This makes it a viable option for large-scale
application to improve fabric functional properties.
Plasma
treatment of textile fabrics is a clean, green process which does not involve
the use of chemicals and water. Plasma treatment thus has great potential for
application to textiles.