90
4 PVA Bionanocomposite Films with Different Particle …
4.5 Topographic Surface Morphology and Surface
Roughness
To assess the nanofiller dispersion within PVA matrices, 3D height mapping images of
PVA and PVA bionanocomposites are exhibited in Fig. 4.4. As illustrated in Fig. 4.4b,
one can see that HNT nanoparticles are separated from one another with better HNT
dispersion in PVA bionanocomposites reinforced with 3 wt% HNTs, as opposed
to typical clay agglomeration and clustering issues beyond 3 wt% HNTs shown in
Fig. 4.4c, d. An excessive amount of HNTs results in decreasing intraparticle spacing
along with higher intramolecular bonding of HNTs leading to particle agglomeration [31]. Besides, the average root-mean-square (R q ) value as an indicator of surface
roughness of PVA bionanocomposites is reported to be 2.4 ± 0.13 nm at the HNT
content of 3 wt% relative to 1.9 ± 0.17 nm for neat PVA, as shown in Fig. 4.4a. It
is suggested that smooth surfaces of PVA/HNT bionanocomposites remain with the
incorporation of HNTs at relatively low HNT contents owing to their uniform dispersion. Such a phenomenon is consistent with PVA/HNT composite hydrogels reported
elsewhere [32]. At the low HNT content of 3 wt%, smooth surfaces of PVA/HNT
bionanocomposites can also be ascribed to the combination of strong interactions
and good compatibility between HNTs and PVA matrices. Nonetheless, increasing
the HNT content up to 5 and 10 wt% induces much higher surface roughness (i.e. R q
= 4.54 ± 0.18 and 13.1 ± 0.23 nm, respectively) owing to the presence of prevalent
HNT aggregates [33].
On the other hand, PVA/Cloisite 30B clay bionanocomposites and PVA/NBC
bionanocomposites reveal different dispersibilities, as compared with PVA/HNT
bionanocomposites. When nanofiller contents were below 10 wt%, spiky nanoparticles appeared to be separated from one another resulting in the homogeneous dispersion of Cloisite 30B clays and NBCs within PVA matrices, Fig. 4.4e, f, as well as
Fig. 4.4h, i, respectively. In particular, as the nanofiller content increased from 3
to 5 wt%, R q values increased moderately from 2.04 ± 0.12 to 2.84 ± 0.18 nm
for PVA/Cloisite 30B clay bionanocomposites, as well as from 2.1 ± 0.11 to 2.5
± 0.16 nm for PVA/NBC bionanocomposite, as opposed to 1.9 ± 0.17 nm for
neat PVA. This finding suggested that smooth surfaces for PVA bionanocomposites were evident at the low nanofiller contents of Cloisite 30B clays and NBCs,
which was in good agreement with previous study in PVA/nanocellulose composite
films [34]. On the contrary, the inclusion of 10 wt% Cloisite 30B clays and NBCs
in PVA bionanocomposites consistently gave rise to increasing R q values up to 6.05
± 0.23 and 4.1 ± 0.19 nm, respectively, which seemed also far higher than that of
neat PVA at 1.9 ± 0.17 nm. Such results signified that the presence of aggregated
Cloisite 30B clays and NBCs resulted in much higher surface roughness on PVA
surfaces as expected. In comparison, the R q value of 4.1 ± 0.19 nm for PVA/NBC
bionanocomposites appeared to be relatively low, as compared with those of other
PVA nanocomposites reinforced with carbon-based fillers such as PVA/reduced GO
(rGO) nanocomposites with a R q value of 4.6 ± 0.55 nm based on deposition layers
[35].
4 PVA Bionanocomposite Films with Different Particle …
4.5 Topographic Surface Morphology and Surface
Roughness
To assess the nanofiller dispersion within PVA matrices, 3D height mapping images of
PVA and PVA bionanocomposites are exhibited in Fig. 4.4. As illustrated in Fig. 4.4b,
one can see that HNT nanoparticles are separated from one another with better HNT
dispersion in PVA bionanocomposites reinforced with 3 wt% HNTs, as opposed
to typical clay agglomeration and clustering issues beyond 3 wt% HNTs shown in
Fig. 4.4c, d. An excessive amount of HNTs results in decreasing intraparticle spacing
along with higher intramolecular bonding of HNTs leading to particle agglomeration [31]. Besides, the average root-mean-square (R q ) value as an indicator of surface
roughness of PVA bionanocomposites is reported to be 2.4 ± 0.13 nm at the HNT
content of 3 wt% relative to 1.9 ± 0.17 nm for neat PVA, as shown in Fig. 4.4a. It
is suggested that smooth surfaces of PVA/HNT bionanocomposites remain with the
incorporation of HNTs at relatively low HNT contents owing to their uniform dispersion. Such a phenomenon is consistent with PVA/HNT composite hydrogels reported
elsewhere [32]. At the low HNT content of 3 wt%, smooth surfaces of PVA/HNT
bionanocomposites can also be ascribed to the combination of strong interactions
and good compatibility between HNTs and PVA matrices. Nonetheless, increasing
the HNT content up to 5 and 10 wt% induces much higher surface roughness (i.e. R q
= 4.54 ± 0.18 and 13.1 ± 0.23 nm, respectively) owing to the presence of prevalent
HNT aggregates [33].
On the other hand, PVA/Cloisite 30B clay bionanocomposites and PVA/NBC
bionanocomposites reveal different dispersibilities, as compared with PVA/HNT
bionanocomposites. When nanofiller contents were below 10 wt%, spiky nanoparticles appeared to be separated from one another resulting in the homogeneous dispersion of Cloisite 30B clays and NBCs within PVA matrices, Fig. 4.4e, f, as well as
Fig. 4.4h, i, respectively. In particular, as the nanofiller content increased from 3
to 5 wt%, R q values increased moderately from 2.04 ± 0.12 to 2.84 ± 0.18 nm
for PVA/Cloisite 30B clay bionanocomposites, as well as from 2.1 ± 0.11 to 2.5
± 0.16 nm for PVA/NBC bionanocomposite, as opposed to 1.9 ± 0.17 nm for
neat PVA. This finding suggested that smooth surfaces for PVA bionanocomposites were evident at the low nanofiller contents of Cloisite 30B clays and NBCs,
which was in good agreement with previous study in PVA/nanocellulose composite
films [34]. On the contrary, the inclusion of 10 wt% Cloisite 30B clays and NBCs
in PVA bionanocomposites consistently gave rise to increasing R q values up to 6.05
± 0.23 and 4.1 ± 0.19 nm, respectively, which seemed also far higher than that of
neat PVA at 1.9 ± 0.17 nm. Such results signified that the presence of aggregated
Cloisite 30B clays and NBCs resulted in much higher surface roughness on PVA
surfaces as expected. In comparison, the R q value of 4.1 ± 0.19 nm for PVA/NBC
bionanocomposites appeared to be relatively low, as compared with those of other
PVA nanocomposites reinforced with carbon-based fillers such as PVA/reduced GO
(rGO) nanocomposites with a R q value of 4.6 ± 0.55 nm based on deposition layers
[35].