Thermogravimetric Properties Of Electromagnetic
Shielding Plain Knitted Composites Using Hybrid Yarn
Devrim Demiray Soyaslan1, İ.İskender Soyaslan2
University of Mehmet Akif Ersoy, Department of Textile Engineering, Turkey
2
University of Mehmet Akif Ersoy, Department of Civil Engineering, Turkey
dsoyaslan@mehmetakif.edu.tr
1
KEYWORDS Composite, yarn, aramid, polypropylene, electromagnetic, shielding.
_____________________________________________________________
OBJECTIVE
Thermogravimetric
properties
of
an
electromagnetic absorbing plain knitted
structure composed of aramıd /polypropylene
/copper blended yarn is investigated in this
study. The composite structure is fabricated by
weft knitting technique on a 7 gauge flat
knitting machine and the composite form is
fabricated under a hot press. The polypropylene
fibers in the yarn melted under heath and
composed the matrix phase. Finally, a knitted
fabric reinforced composite is developed that
has 15 dB EMS (Electromagnetic Shielding)
value in the frequency range of 27-500 Mhz and
good thermogravimetric properties.
INTRODUCTION
Conductive fabrics and their composites are still
in great interest in the electromagnetic
interference (EMI) shielding research area due
to their interesting physical and thermal
properties. There is an increasing need to limit
the EMI with the well development of wireless
communications, electrical and electronic
devices. [1-5]
Most of the shielding materials consist of
metals. Scientific literature indicates that fiberfiled plastics, coated plastics, conductive
laminates, composites, some fabrics and fabric
reinforced composites have been developed to
replace metals for many applications, which
have advantages such as light weight, physical
flexibility and good electrical properties. [6,7]
EXPERIMENTAL APPROACH
Materials
Aramid/polypropylene/copper blended yarn is
formed by a yarn-folding machine. Plain knitted
structure is produced by a 7G flat knitting
machine and the composite form is developed
by a hot laboratory press. So plain knitted fabric
reinforced composites that have 15 dB EM
shielding effectiveness in the frequency range of
27-500 Mhz and 1.5 mm thickness are
developed. The microstructure of the composite
is shown in Figure 1. The yarn properties used
in the knitted fabric are summarized in Table.1.
Table.1. Yarn Properties in Plain Knitted Structure
Yarn Properties in Plain Knitted Structure
Aramid yarn
PP yarn
Copper wire
17/1 Nm
300/72 denier
0.15 mm
Methods
The composites are tested in thermal
gravimetric analyzer (TGA) and differensial
thermal analyzer (DTA) up to 6000C.
RESULTS AND DISCUSSION
As seen in Figure. 2, the composite structure has
decomposed at two stages. Fist decomposition is
occurred at 290-4780C and the second
decomposition is occurred at 478-5850C. %15.5
mass loss is observed after the first
decomposition and %11.5 mass loss is observed
after the second decomposition. So that total
loss in mass is obtained %26.5. The
decomposed material in the composite was
polypropylene. The polypropylene yarn melted
and vaporized after 2900C and this situation
explains the mass loss in the composite
material.
The copper wire and the aramid yarns didn’t
decompose during heating until 6000C.
Figure 1: Photomicrograph of composite by SEM
8.000
212.8Cel
9.313mg
300.0
0.350
289.8Cel
9.280mg
250.0
9.000
1.377mg
7.000
0.300
6.000
0.250
8.500
5.000
4.000
478.2Cel
7.903mg
150.0
3.000
8.000
0.150
1.009mg
100.0
2.000
7.500
0.100
1.000
50.0
0.050
0.000
7.000
587.9Cel
6.883mg
100.0
200.0
300.0
Temp Cel
400.0
500.0
Figure 2: TGA and DTA graphics of plain knitted composite
CONCLUSIONS
A fabric reinforced composite material is
developed in this study. The composite material
that has 15 dB EM shielding value in the
frequency range of 27-500 Mhz showed good
thermal properties. In TGA analysis the material
didn’t decompose until 290 0C .This means PP
fibers are melted at 160-164 0C which is the
melting degree of polypropylene but didn’t
vaporized until 290 0C so that any mass loss
didn’t occure up to this temperature. After
290 0C, two stage decomposition is occurred
and total loss in mass is obtained as %26.5.
The composite developed in this study is
suitable for many electromagnetic shielding
applications due to its thermal properties.
FUTURE WORK
Two or multi-layered composites are planning
to be developed in future studies.
ACKNOWLEDGMENTS
The EMSE results in this study were obtained
from PhD thesis of Devrim Demiray Soyaslan
and thanks to The Scientific and Technological
Research Council of Turkey funding thesis.
REFERENCES
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.
DTG %/Cel
0.200
TG mg
DTA uV
DTG ug/min
200.0