Annual Report 2012 - Latvijas Universitātes Cietvielu fizikas institūts

Flax and Hemp Fiber Functionalization Studies
A. Lusis, E. Pentjuss, J.Gabrusenoks , R.Janeliukštis, L.Veļķere, J.Zandersons,
J. Balodis
Impedance spectroscopy of metal coated fabrics
Sustainable development of technical textiles is associated with natural fibers to replace
the oil-producing fibers. In this context, it is
necessary to carry out studies on the flax and hemp
fiber and fabric functionalization for technical
applications. The natural fibers (NF) as well as
fabrics (FF) themselves are porous media. The
porous media usually adsorbs some chemicals from
environment. One of them is water and content of
moisture in fabrics have to be controled.
Metal coatings are widely used for functionalization
of fabrics for different technical applications. To
characterize the metal coating is a problem in itself.
First of all, to functionalize fibers or fabrics is to
examine the content of moisture and its role on
mechanical and physical properties. The impedance
spectroscopy (IS) has been used to study moisture in
1
4
10 7
2
10 6
10 5
5
3
10 4
10 3
6
7
10 2
10 2 10 3 10 4 10 5 10 6 10 7
10 8 Frequency (Hz)
FF and metal coated fabrics (M/FF/M). The impedance spectra of such samples are
complicate due to heterogeneous and nonhomogeneous constitution.
|Z|
1- HF from store
2- HF 1 day in 100% RH
3- HF 27 days in 100% RH
4- FF from store
5- FF 1 day in 100% RH
6- FF 27 days in 100% RH
7- Al/FF/Al wet
Fig.1.Impedance spectra of flax
and hemp fabrics
The water content has strong
influence on impedance modulus
|Z| spectra (Fig.2). Analyses of |Z|
spectra with simulation of
equivalent circuit models, the best
fit have been obtained with CPE
for wet samples (Fig.2) and RC
elements for dry samples. The
value of capacitance C depends on
water content and can be used for
controle of moisture content in flax
and hemp fabrics.
Thermomechanical properties of metal coated hemp yarns
TGA shows two weight loss temperature areas of 30-110 O C (moisture retention) and
200-300 O C (hemp fiber carbonization). The thermo-mechanical strength of unmodified
and modified hemp yarns is presented on Fig.3.
TGA
%
100.00
80.00
60.00
40.00
20.00
Cu
Cu2O
Non treated yarn
-3.700 %
-3.930 %
-5.416 %
-61.650 %
-77.121 %
-79.752 %
0.00 100.00 200.00 300.00 400.00 500.00
Temp [C]
Fig.2. Equivalent circuit models for wet samples
M/NF/M
R1= 0-2 Ohm R2≈R3=1-10 Ohm,
CPE1=0,1-100 μF
CPE3=5-1000 nF
127
DTA
uV
400.00
200.00
0.00
Cu
Cu2O
Non treated yar
97.36 C
CPE2= 50-1000 pF
L1=10-100 nH
394.55 C
367.89 C
372.13 409.01 C C
435.38 C
380.10 C
357.19 C
431.21 C
-200.00
98.65 C
94.56 C
0.00 100.00 200.00 300.00 400.00 500.00
Temp [C]
Fig. 3. TGA shows two weight loss temperature areas of 30-110 O C (moisture retention) and 200-300 O C (hemp fiber
carbonization).