Page 611 - Polymer-based Nanocomposites for Energy and Environmental Applications

564 Polymer-based Nanocomposites for Energy and Environmental Applications

splitting [17]. Due to the constrictions of electospinning, several studies were also per-
formed using those nonelectrofiber spinning techniques. Jackiewicz and Werner [18]
used a modified melt-blowing device that is able to produce nanofibrous nonwoven
filters at industrial scale. Polypropylene granules with an MFI value of 1800 MFI
were preferred due to its lower viscosity. Nanoscale KCl solid particles (in cubic
shape) and diethylhexyl sebacate (DEHS) liquid particles (in spherical shape) were
used for filtration efficiency measurements, which are recommended for
EN779:2012 and EN1822:2009 filtration efficiency test standards. It was seen that
the shape of nanoparticle does not have any effect on filtration efficiency. Besides,
the effect of aerosol face velocity and the filter media morphology over filtration effi-
ciency and pressure drop were examined. According to the test results, the filtration
efficiency increases with a decrease in fiber diameter. Moreover, aerosol flow velocity
affects the filtration efficiency adversely. Three different filter samples were produced
with names F0.5 (average fiber diameter is nearly 0.5 μm), F5 (average fiber diameter
is nearly 5 μm), and F10 (average fiber diameter is nearly 10 μm). The highest effi-
ciency was obtained from F0.5 filter sample, which exhibited a capture performance
of 91.19% at 0.05 m/s face velocity, while it was 83.13% for F5 filter sample and
68.76% for F10 filter sample [18].
Sinha-Ray et al. [19] studied filtration properties of nanoparticles via producing
nanofibers by solution blowing as a nonelectrospinning nanofiber production tech-
nique. Nanofibers were produced with diameter of 20–50 nm range. The aim of the
study is to increase the filtration performance of commercial filter media by incorpo-
rating a nanofibrous layer. Researchers modified three different filters with three
different fibers: (a) electrospun fibers, (b) electrically assisted solution-blown
nanofibers, and (c) dual coating with electrospun nanofibers and solution-blown nano-
fibers. Electrically assisted solution-blown nanofibers (in the range of 20–50 nm)
were significantly thinner than electrospun nanofibers (300 nm). Dual coating
includes base filter as electrospun nanofibers, and then, solution-blown nanofibers
were deposited on top of them. Formation of ultrafine nanofibers proposes an effective
mechanism of nanoparticle inception, and attractive van der Waals forces should
greatly increase the filtration efficiency. Thinner solution-blown nanofibers have
more efficient barrier properties compared with larger electrospun nanofibers. Also,
results show that filters modified with dual coating were most effective to remove
Cu nanoparticles from aqueous suspensions. It is predicted that nanoparticles should
accumulate on the smallest nanofiber surfaces [19].
Another nonelectrospinning technique is the centrifugal spinning to produce
ultrafine nanofibers. Krifa and Yuan fabricated nanofiber membranes using two diffe-
rent methods: electrospinning and centrifugal spinning. Barrier properties of these
membranes were compared. The results showed that fiber diameter increases with
higher concentrations in both spinning methods. At an expense of larger productivity,
centrifugally spun nanofibers have broader diameter distributions than electrospun
nanofibers, which causes larger particle penetration [20].
Liu et al. [21] produced bimodal polyamide-56 (PA-56) nanofiber/nets (NFN)
consisting of interconnected ultrathin nanowires (about 20 nm) and steady cavity
constructed with bonded fibers by using one-step electrospinning/netting. First of