Page 608 - Polymer-based Nanocomposites for Energy and Environmental Applications

Nanofibrous composite air filters 561

They also introduced PU within PAN nanofibers using simultaneously working
needles, which was schematically shown in Fig. 20.6 with PAN-11 and PU. The
aim of the PU was to increase bonding of fibers, hence improving the mechanical per-
formance of the membrane. Interestingly, the incorporation of PU caused an increase
in the air permeability. The final effort in improving filtration efficiency and making
membrane superamphiphobic has been to incorporate FPU to PAN-11/PU during
nanofiber production. The FPU content makes the surface energy of filter media lower
2
as 18.08 mJ/m and thus makes functional filter structures. According to the filtration
efficiency test results, the composite filter media can capture the oil aerosol particles
with >99.9% (HEPA) due to the effect of surface roughness and the fiber diameter [1].
In another study, Liu et al. [5] aimed to produce nanofibrous air filter samples to be
used as HEPA filter medium. For that, poly(acrylic acid) (PAA) was blended with
PAN to increase the mechanical properties of filter sample. PAN/PAA solution with
weight ratios 3:7, 4:6, 5:5, 6:4, 7:3, and 10:0 was used for the production of nanofibers.
For the 100% PAN samples, the samples exhibited the highest tensile strength as
shown in Fig. 20.8, while samples produced using 7 wt% polymer concentration
were the most rigid. Though 13% PAN solution exhibited the lowest filtration
efficiency, due to lower pressure drop, the highest QF was obtained from that sample.
Sodium chloride aerosol particles with 300–500 nm size were used for the filtration
performance test. Tests were conducted at a face velocity of 5.3 cm/s through
filter medium. PAN/PAA solution with 6:4 weight ratio performed the best efficiency
value of 99.994% at an expense of 160 Pa pressure drop value, which is the lowest one
compared with other ratios of PAN/PAA as clearly seen in Fig. 20.8. PAN/PAA
(6:4)-based nanofibrous webs also showed the largest average pore size with a value
of 44.4 nm, which showed the pore size effect on efficiency clearly. The QF also
showed that PAN/PAA with 6/4 weight has the highest filtration performance with
1
highest QF of 0.032 Pa .
Zhang et al. [15] produced antideformed polyethylene oxide (PEO)@polyacrylo-
nitrile (PAN)/polysulfone (PSU) fiber membranes with smaller pore sizes and low

0.035
380
100.00
360
99.99 0.030
340
99.98 320 0.025
Filtration efficiency (%) 99.96 280 Pressure drop (pa) Quality factor (Pa −1 ) 0.020
300
99.97
260
99.95
240
99.94
0.015
220
99.93
200
99.92
180 0.010
99.91 160
99.90 140 0.005
3/7 4/6 5/5 6/4 7/3 10/0 3/7 4/6 5/5 6/4 7/3 10/0
(A) PAN/PAA (w/w) (B) PAN/PAA (w/w)
Fig. 20.8 (A) The filtration efficiency and the pressure drop, (B) the quality factor of
samples [5].