217 CHAPTER 9 NANO SILVER FINISHING OF COPPER CORE YARN FABRIC TO IMPROVE THE EMSE 9.1 INTRODUCTION Nanotechnology protective treatment is the latest trend in textile finishing and has been proved to be a useful technology in improving the performance of textiles. In this present work, the electromagnetic shielding effectiveness of silver nanofinish copper core yarn fabrics were studied and explained in this chapter. The silver nanoparticles were applied on woven plain fabric by pad-dry process. Silver nanoparticles were applied on copper core yarn woven plain fabric using three different variables namely concentration, application temperature and curing time. Sixteen samples were taken for application of silver nanoparticles and testing by using Factorial Design method of analysis. The electromagnetic shielding effectiveness values for different applying conditions were measured, tabulated and discussed in this chapter. 9.2 RESULT AND DISCUSSION 9.2.1 Surface morphology of Silver Nano-particles - SEM Lower levels of magnification (2500 X) of copper core yarn cotton fabric samples, treated with nano-silver (20 ml/l), showed clear images of fibres with surface level cracks associated with them, in the middle of the fibre and, the inherent convolutions of the cotton fibres (Figures 9.1 and 9.2).
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217
CHAPTER 9
NANO SILVER FINISHING OF COPPER CORE YARN
FABRIC TO IMPROVE THE EMSE
9.1 INTRODUCTION
Nanotechnology protective treatment is the latest trend in textile
finishing and has been proved to be a useful technology in improving the
performance of textiles. In this present work, the electromagnetic shielding
effectiveness of silver nanofinish copper core yarn fabrics were studied and
explained in this chapter. The silver nanoparticles were applied on woven
plain fabric by pad-dry process. Silver nanoparticles were applied on copper
core yarn woven plain fabric using three different variables namely
concentration, application temperature and curing time. Sixteen samples were
taken for application of silver nanoparticles and testing by using Factorial
Design method of analysis. The electromagnetic shielding effectiveness
values for different applying conditions were measured, tabulated and
discussed in this chapter.
9.2 RESULT AND DISCUSSION
9.2.1 Surface morphology of Silver Nano-particles - SEM
Lower levels of magnification (2500 X) of copper core yarn cotton
fabric samples, treated with nano-silver (20 ml/l), showed clear images of
fibres with surface level cracks associated with them, in the middle of the
fibre and, the inherent convolutions of the cotton fibres (Figures 9.1 and 9.2).
218
Treatment with the suspensions of nano-silver resulted in the deposition and
firm attachment of silver particles over the surface of the fabrics. However,
such deposits appeared to be concentrated in certain places, which obviously
could result in agglomeration of the particles. Surface deposits of nano-
particles, concentrated in the localized way, over the fabric surface can be
expected to scatter the electromagnetic interference rays rather than resulting
a uniform reflection. The samples treated with higher concentration levels of
silver nano-particles showed higher deposits on to the surface of fibres than
the samples treated with low concentration levels (Figure 9.2). The difference
in concentration levels are expected to have different levels of influence on
the electromagnetic shielding effectiveness against electromagnetic
interference.
Magnification at higher levels (15000 X), for the samples treated
with low and high concentration levels of nano-particles, revealed the surface
deposits of that were mainly aggregated to an extent of ~ 500 nm (Figure 9.3).
Also, the deposits were found to be high near the asperities, surface cracks
and cross-over points between the fibres, which could exercise additional
holding by trapping the nano-particles, compared to the smooth surfaces of
the fibres. The significant amounts of nano-particles that appeared to be
present throughout the fibre surface, are expected to have considerable
influence on the electromagnetic shielding properties of the fabrics. When
such depositions are present in the fabric samples with the yarns made of
conductive core yarns, more attenuation can be expected from those samples.
219
Figure 9.1 Samples treated with low concentration of silver nano-
particles - SEM
Figure 9.2 Samples treated with high concentration of silver nano-
particles- SEM
220
Figure 9.3 Deposits of Silver Nano-particles at higher magnification
levels (15000 X) - SEM
9.2.2 Antibacterial Effects of Silver Nano Finished Fabric
Nanosized silver particles in colloidal solution had excellent
antibacterial effect on all specimens against gram-positive and gram-negative
bacteria. Table 5.4 shows the antibacterial effect of nanosized silver colloidal
solution on processed fabric. It is found that the bacterial reductions of all
samples were very excellent against E-coli.
In this study, the applications of silver Nanoparticles were
investigated by growing E.coli on agar plates. When Nanoparticles were
present on agar plates, they could completely inhibit the bacterial growth.
However, inhibition depends upon concentration of silver Nanoparticles.
In contrast, silver Nano particles in liquid medium, even at higher
concentration, caused only delayed growth of E.coli. The concentration of
nano particles decreases, allowing resumed growth of bacterial cells.
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It is well known that outer membrane of E.coli cells is
predominantly constructed from tightly packed lipopolysaccharides
molecules, which provide an effective permeability barrier. It is clear that
treated bacteria also showed significant changes in and damages in the
membranes. The fabrics padded through 30 ml/l silver colloidal solution also
had better bacterial activity than the samples treated with 20 ml/l and 10 ml/l
solution at 22°C as shown in the Table 9.1. Results obtained in the
antimicrobial test shows that, silver concentration at 10 ml/l and temperature
at 22°C the antimicrobial activity increases with increase in curing time. The
higher bacterial inhibition also obtained at 30 ml/l and 22°C with the increase
in curing time. The bacterial inhibition at 20°C is very less when compared to
22°C and 24°C with increase in curing time as shown in the Table 9.1.
Table 9.1 Antimicrobial Activity of Nano Silver finished Fabrics
S.No. X1 in ml/l X2 in °C X3 in min Antimicrobial activity Diameter of clearance