Application of graphene from exfoliation in kitchen mixer allows mechanical reinforcement of PVA/graphene film
Appl Nanosci
Application of graphene from exfoliation in kitchen mixer allows mechanical reinforcement of PVA/graphene film
Zulhelmi Ismail 0 1 2
Abu Hannifa Abdullah 0 1 2
Anis Sakinah Zainal Abidin 0 1 2
Kamal Yusoh 0 1 2
0 & Zulhelmi Ismail
1 Faculty of Chemical Engineering and Natural Resources , Universiti Malaysia Pahang, 26300 Kuantan, Pahang , Malaysia
2 Faculty of Manufacturing Engineering , Universiti Malaysia Pahang, 26600 Pekan, Pahang , Malaysia
Mechanical properties of polyvinyl alcohol (PVA) can be reinforced from the addition of graphene into its matrix. However, pristine graphene lacks solubility in water and thus makes dispersion a challenging task. Notably, functionalisation of graphene is required to accommodate graphene presence in the water. In this work, we have used a kitchen mixer to produce gum Arabicgraphene (GGA) for the first time as filler for mechanical reinforcement of PVA. For the characterisation of exfoliated graphene, mean lateral size of GGA was measured from the imaging by transmission electron microscopy while the mean thickness of graphene was predicted from the obtained spectra by Raman spectroscopy. During the preparation of PVA/graphene film by solution casting, GGA was varied between 0, 0.05, 0.075, 0.10 and 0.15 wt% in concentration. We found that the presence of GGA in PVA improves the tensile stress and elastic modulus about 72-200 and 19-187% from the original values. The data from Halpin-Tsai meanwhile suggested that the mechanical reinforcement of PVA/graphene film is due to the random distribution network of GGA in PVA.
Graphene; Gum Arabic; Exfoliation; Kitchen mixer; Mechanical reinforcement; PVA/graphene
Introduction
Polyvinyl alcohol (PVA) is a synthetic polymer that is
produced from the chemical conversion of polymerised
vinyl acetate in a hydrous methanol
(Cline et al. 1952)
. In
addition to zero toxicity, the presence of high number of
OH bonds in PVA is also allowing high solubility of PVA
in water. Despite these advantages, the reported values of
tensile strength, r (15.7?74 MPa) for pristine PVA
(Chen
et al. 2005; Liang et al. 2009; Liu et al. 2005)
are
remarkably lower than that of industrial polymer such as
nylon 6
(Cho and Paul 2001; Zhang et al. 2004)
. To
improve the mechanical characteristic of PVA,
reinforcement by filler is very important as the selected filler must
not only enhance the tensile strength of PVA, but also have
good interfacial interactions with PVA.
Due to the excellent mechanical properties of graphene,
it is the most suitable candidate for mechanical
improvement of PVA. However, pristine graphene is hydrophobic
in nature and this makes the dispersion of graphene in a
hydrophilic polymer like PVA unfeasible. To overcome
this challenge, graphene oxide (GO) was commonly used
as a filler for PVA due to high solubility of GO in water
(Liang et al. 2009)
. The H-bonding between PVA and GO
was suggested as a major mechanism in homogeneous
distribution of GO in the matrix of PVA. Moreover, the
pre-dispersion of GO in PVA would allow reduction of GO
to graphene, as been demonstrated by the change from a
brownish film of PVA to opaque black after the reduction
stage of the PVA/GO film
(Kashyap et al. 2016; Zhou et al.
2011)
. Currently, functionalisation of graphene with PVA
has even been reported for better distribution of graphene
in the matrix
(Arao et al. 2016)
. In their work, sonication
and pressure homogeniser were used in the exfoliation of
graphite to graphene.
While better mechanical performance was observed for
PVA with the incorporation of PVA?graphene synthesised
by pressure homogeniser, the application of kitchen mixer
as a tool for preparation of gum Arabic-graphene (GGA) in
the mechanical reinforcement of PVA until now has never
been discussed. A majority of works on PVA/graphene
composite used sonication as a method for production of
graphene
(Al Islam et al. 2016; Jan et al. 2016)
. It is
expected that the presence of biocompatible GGA in the
matrix would allow the future usage of PVA as material for
biomedical and biological application. Therefore, it is
important to show that the mechanical reinforcement of
PVA can still be achieved from the incorporation of GGA
by a kitchen mixer as an exfoliating device.
Herein, we report the application of shear exfoliated
GGA as filler for the mechanical reinforcement of PVA.
The graphene was prepared from the mixing of graphite
and gum Arabic in a kitchen mixer of 800 W. We found
that GGA was easily dispersed in the solution of PVA and
the resulting PVA/graphene film performed mechanically
better than original PVA. In addition, the developed
PVA/graphene film also has higher thermal stability than
that of pure PVA.
Results and discussion
Characterisations of graphene
To establish that the graphene indeed was produced during
the exfoliation in a kitchen mixer, the imaging of graphene
in the supernatant was carried out by transmission electron
microsc (...truncated)