Biomedical Engineering Reference
In-Depth Information
2.5
2.0
1.5
1.0
0.5
0.0
0
3
6
9
12
CNXL Content (wt%)
Figure 10.8
Tensile modulus of polysulfone film filled with CNXLs formed via phase
inversion.Thefilmswere
∼
20
µ
mthick(Nooranietal.2006).
It has been observed an increase in modulus in the system polysulfone (PSf)-CNXL
(Figure 10.8) up to
7% CNXL weight %. At higher concentrations the modulus
decreased. It was concluded that this was due to agglomeration of the CNXLs, as
confirmed by SEM images of the fracture surfaces of the films. Since these PSf/CNXL
films were prepared by phase inversion, i.e. taking a PSf solution dissolved in N-methyl
pyrrolidone (NMP) and submerging it in warm water, the films are porous. However,
the pores were small since the resulting films were clear and as confimed by SEM
images. This explains the observed moduli being lower than that reported for pure PSf
(2.48 GPa) (Solvay 2006). However, the addition of CNXLs increased the modulus
significantly, with the modulus of the 7%-load sample 2.8 times that of the unfilled
PSf. The large variability in the data is typical for phase inversion samples fabricated
in a laboratory. SEM indicated that the size of the pores did not change greatly with
CNXL content, although this may also be a source of variability in the samples.
∼
10.6
Transport Properties
In addition to the reinforcing effect, it is well known that CNXLs affect the performance
of nanocomposites, from example, by improving the barrier properties and thus the mem-
brane performance, depending upon the filler particle type and its interfacial interactions.
Indeed, the permeability has been seen to increase without sacrificing selectivity (Aerts
et al
. 2000a; Aerts
et al
. 2000b; Merkel
et al
. 2002; Naidu
et al
. 2005; Sacca
et al
.
2005; Yan
et al
. 2005). The effect can be especially pronounced in the case of nanopar-
ticle fillers (Aerts
et al
. 2000a; Aerts
et al
. 2000b; Aminabhavi and Mallikarjuna 2004).
The mechanism of this effect of nano-sized filler particles is perhaps not entirely under-
stood, but it is generally accepted that the effect of the interphase between filler and
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