66
3 PVA/BC Bionancomposite Films with Particle Size Effect
However, such lowest strength levels still appear to be above that of neat PVA.
Overall, both tensile moduli and tensile strengths of PVA/NBC bionanocomposites
are consistently superior to those of PVA/MBC bionanocomposites, as illustrated
in Fig. 3.7a. This phenomenon suggests the importance of particle size effect that
smaller particles with larger surface areas on nanoscaled levels and good particle
dispersion can yield better mechanical properties of bionanocomposites. As a matter
of fact, when compared with MBCs, NBCs have relatively large surface areas,
Table 3.2. Accordingly, more uniform particle dispersion of NBCs induces stronger
interfacial bonding between NBCs and PVA matrices for effective load transfer from
nanofillers to matrices, which may be the major reason for a further strength increase
in PVA/NBC bionanocomposites.
In addition, both elongation at break and tensile toughness are decreased significantly by maximum 66 and 58% for PVA/NBC bionanocomposites, as well as
66.8 and 66.4% for PVA/MBC bionanocomposites, respectively, when increasing
the BC content from 0 to 10 wt%, as opposed to those of PVA, Fig. 3.7b. The addition of MBCs gives rise to a more remarkable decreasing trend for elongation at
break relative to the inclusion of NBCs. Such a trend becomes less pronounced as
far as tensile toughness is concerned. Generally, the inclusion of more rigid fillers
inevitably improves elastic moduli and enhances the brittle nature (as reflected from
smaller elongation at break) relative to those of neat polymers so that nanocomposites
become much stiffer than corresponding unfilled polymers. The other point worth
mentioning is that the decreases in tensile strength and tensile toughness of PVA/BC
bionanocomposites at higher BC contents up to 10 wt% are most likely to be associated with BC particle agglomeration due to weak particle–particle van der Waals
interactions, thus resulting in high stress concentration zones prone to mechanical
failure.
Figure 3.7c demonstrates the comparison of tensile strengths of PVA/NBC
bionanocomposites and PVA/MBC bionanocomposites with other PVA nanocomposites available in previous literatures [32–39]. Xu et al. [32] reported that the
tensile strength of PVA was increased by 70% with the inclusion of 3 wt% GOs due
to strong interfacial bonding between PVA and GOs according to their XRD analysis. Arao et al. [33] stated that the incorporation of 0.25 wt% of few-layer-graphene
(FLG) into PVA matrices enhanced tensile strength of PVA/FLG nanocomposites by
15% because uniform FLG dispersion enabled to form stronger interfacial bonding
with PVA matrices. Furthermore, Liu et al. [34] functionalised SWNT surfaces with
multiple hydrogen bonding groups to improve SWNT dispersion in PVA/SWNT
nanocomposites. Their tensile strength was found to be improved by 44.6% at the
SWNT content of 0.8 wt%, when compared to that of neat PVA. The use of hybrid
nanofillers was also presented by Li et al. [35] to achieve increases in tensile strengths
of PVA nanocomposites by 57.5 and 75.6% when embedded with 1 wt% MWNTs and
2 wt% GOs, as well as 2 wt% MWNTs and 4 wt% GOs, respectively. This is because
hybrid MWNT/GO reinforcements can achieve much stronger interfacial interactions with PVA matrices leading to higher tensile strengths of their corresponding
nanocomposites. On the other hand, Morimune et al. [36] mentioned that with the
3 PVA/BC Bionancomposite Films with Particle Size Effect
However, such lowest strength levels still appear to be above that of neat PVA.
Overall, both tensile moduli and tensile strengths of PVA/NBC bionanocomposites
are consistently superior to those of PVA/MBC bionanocomposites, as illustrated
in Fig. 3.7a. This phenomenon suggests the importance of particle size effect that
smaller particles with larger surface areas on nanoscaled levels and good particle
dispersion can yield better mechanical properties of bionanocomposites. As a matter
of fact, when compared with MBCs, NBCs have relatively large surface areas,
Table 3.2. Accordingly, more uniform particle dispersion of NBCs induces stronger
interfacial bonding between NBCs and PVA matrices for effective load transfer from
nanofillers to matrices, which may be the major reason for a further strength increase
in PVA/NBC bionanocomposites.
In addition, both elongation at break and tensile toughness are decreased significantly by maximum 66 and 58% for PVA/NBC bionanocomposites, as well as
66.8 and 66.4% for PVA/MBC bionanocomposites, respectively, when increasing
the BC content from 0 to 10 wt%, as opposed to those of PVA, Fig. 3.7b. The addition of MBCs gives rise to a more remarkable decreasing trend for elongation at
break relative to the inclusion of NBCs. Such a trend becomes less pronounced as
far as tensile toughness is concerned. Generally, the inclusion of more rigid fillers
inevitably improves elastic moduli and enhances the brittle nature (as reflected from
smaller elongation at break) relative to those of neat polymers so that nanocomposites
become much stiffer than corresponding unfilled polymers. The other point worth
mentioning is that the decreases in tensile strength and tensile toughness of PVA/BC
bionanocomposites at higher BC contents up to 10 wt% are most likely to be associated with BC particle agglomeration due to weak particle–particle van der Waals
interactions, thus resulting in high stress concentration zones prone to mechanical
failure.
Figure 3.7c demonstrates the comparison of tensile strengths of PVA/NBC
bionanocomposites and PVA/MBC bionanocomposites with other PVA nanocomposites available in previous literatures [32–39]. Xu et al. [32] reported that the
tensile strength of PVA was increased by 70% with the inclusion of 3 wt% GOs due
to strong interfacial bonding between PVA and GOs according to their XRD analysis. Arao et al. [33] stated that the incorporation of 0.25 wt% of few-layer-graphene
(FLG) into PVA matrices enhanced tensile strength of PVA/FLG nanocomposites by
15% because uniform FLG dispersion enabled to form stronger interfacial bonding
with PVA matrices. Furthermore, Liu et al. [34] functionalised SWNT surfaces with
multiple hydrogen bonding groups to improve SWNT dispersion in PVA/SWNT
nanocomposites. Their tensile strength was found to be improved by 44.6% at the
SWNT content of 0.8 wt%, when compared to that of neat PVA. The use of hybrid
nanofillers was also presented by Li et al. [35] to achieve increases in tensile strengths
of PVA nanocomposites by 57.5 and 75.6% when embedded with 1 wt% MWNTs and
2 wt% GOs, as well as 2 wt% MWNTs and 4 wt% GOs, respectively. This is because
hybrid MWNT/GO reinforcements can achieve much stronger interfacial interactions with PVA matrices leading to higher tensile strengths of their corresponding
nanocomposites. On the other hand, Morimune et al. [36] mentioned that with the