JEC COMPOSITES MAGAZINE - Issue #95 - Special JEC Europe - March 2015 - 96

graphene

Fig. 1: Rotating plasma reactor drum:
the central point is the electrode that emits the
plasma, nanomaterials are introduced into the
chamber and the plasma functionalises the
surface of the particles

Geim and Novoselov in 2004, potential
applications have been appearing in a
wide range of industries including highperformance composites, packaging,
electronics, sensors and energy storage.
By using graphene, which is inherently cheap, abundant and renewable,
manufacturers can also begin to reduce
the environmental impact of obtaining
rare materials while also significantly
lowering the cost of the manufacturing
process.
Nanocarbons - like graphene nanoplatelets (GNPs) and carbon nanotubes
- are ideal for composite reinforcement
as they exhibit incredible properties
and are extremely lightweight. Due to
their size, they are unlikely to be used
to manufacture pure graphene applications, however they have considerable
potential as an additive. By combining
small quantities of GNPs with a host
matrix, it is possible to significantly improve the properties of the end product.
However, nanomaterials such as these
are naturally inert and have low surface
energy, increasing the difficulty in forging strong chemical bonds with the host
material. As a result, it is difficult to
engineer a solution that displays the full
capability of graphene's advantageous
properties in order to realise its true
potential and it is first necessary to find
a suitable method of functionalisation.

Functionalising graphene
for material reinforcement
The key to achieving optimal mechanical properties in any composite material

Fig. 2: Rotating plasma reactor nanomaterial, the second stage is to choose a functionalising group and
the final stage is to specify the desired amount of chemical functionalisation to achieve optimal properties
in the end product

is a uniform dispersion of the additive
within the host matrix. This ensures
that there are no structural weaknesses
that can cause fractures or deformation
by providing uniform reinforcement
throughout the composite. There are
several existing technologies that attempt to harness graphene's properties
through functionalisation, however the
benefits of using these techniques are
often outweighed by the costs, both
financially and environmentally. Many
of these existing processes employ
chemical and thermal treatment agents
in order to successfully functionalise
the nanomaterials and facilitate better
dispersion within the host matrix.
However, chemical treatments, which
require aggressive acid groups, can
cause extensive damage to the graphene
and deteriorate the quality of the end
product. The use of such compounds
also generates additional costs in terms
of post-processing disposal and implicates serious environmental concerns.

Low-temperature
plasma functionalisation
In composites manufacturing, the
most important factor is the interface
between the GNPs and the host matrix.
This can significantly affect the properties of the composite end product; it is
therefore of paramount importance to
achieve effective chemical bonding. As
graphene requires surface chemicals in

96 jec composites magazine / No95 March 2015

order to increase its ability to bond with
other materials, it is important to be
able to control the amount of chemicals
present on the surface of the graphene
particles. With the optimal level of
chemical functionalisation, the possibility of successfully achieving chemical
bonding with the matrix increases and
is more likely to facilitate homogeneous dispersion of the GNPs. Lowtemperature plasma functionalisation
is a recently developed technology that
can achieve the full commercialisation
of graphene for composite solutions
(Fig. 1).
This scalable process is capable of
functionalising a wide range of nanomaterials including graphene, providing
application manufacturers with a choice
of raw materials that best suit the end
product. It is also able to functionalise
with a wide range of chemical groups,
which can be tailored to specification,
satisfying the needs of the intended
application (Fig. 2). Because the process does not utilise wet chemistry or
functionalising acids, it does not cause
damage to the graphene nanoparticles.
In addition, the low-temperature aspect
means it requires considerably less energy than other methods, further reducing production costs and the absence
of a waste stream is environmentally
beneficial.
JEC COMPOSITES MAGAZINE - Issue #95 - Special JEC Europe - March 2015

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