Plastics & Rubber World - November/December 2019 - 16

graphene

›› Continued from page 14

With sustainability in mind, does
graphene require virgin polymer as the
material base? "We get really good results with virgin, as you would expect, but
there's a lot of development around reclaimed material. The problem with that is
that it never performs as well as the virgin
polymer."
Should reclaimed material be the material of choice, it is possible that graphene
can help restore the mechanical properties of that material to where it has the
same performance as virgin. "It's the same
for biopolymers, they don't have the same
performance as more traditional materials. Again, the argument is whether adding

graphene to a starch-based polymer can
make them behave like a more traditional
polymer," says Ricketts.
Asked whether a plastic product which
has graphene as part of its material mix
can be recycled, Ricketts has a surprising answer: "We don't really know. The
volumes have not been high enough to
where we need to have a conversation
about that. What we do know is that the
loadings we're using are really low, anywhere from .25% by weight, up to 3.0%.
We know they can be reused, but we don't
know is how many times they can be reused - that would be an interesting research project."

performance figures

Work boots produced using graphene supplied by Australian
company First Graphene

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First Graphene, with headquarters
in Henderson, Western Australia and
UK offices in Manchester, is another
leading supplier of graphene. Dr. Andy
Goodwin (pictured), chief technology
officer, agrees that the material can
boost the performance of most polymers.
"Graphene can be used as an additive in a wide range of materials, including elastomers, thermosets and
fibre-reinforced composites. Its addition has been shown to
deliver a range of desirable characteristics, including improvements to mechanical strength, stiffness and fire resistance,
wear and chemical resistance. Graphene additives can also enhance the ability of materials to act as a barrier to liquids and
gases and increase their electrical and thermal conductivity."
Dr. Goodwin puts forward some figures to go along with the
demonstrated benefits. Specifically, adding 0.1% of graphene
nanoplatelets by weight to ultra-high molecular weight polyethylene can increase tensile strength by 71% and fracture
resistance toughness by 54%.
Looking at polypropylene, adding 0.42% of graphene material delivers a 75% increase in yield strength and a 74% increase in Young's modulus (the ability of a material to withstand changes in length when under lengthwise tension or
compression).
Finally, in a polyurethane elastomer, the addition of 1.0%
of graphene platelets increased the limiting oxygen index, an
important measure of fire resistance, from 22.85% to 31.6%.
Dr. Goodwin continues: "The mechanical performance
of graphene platelets is closely related to their aspect ratio,
which describes the width and length of the platelets in comparison with their thickness.
"This means that, where graphene is used as a polymer additive, fewer layers do not necessarily equate to higher performance. These applications benefit most from the use of large
platelets with a length and width greater than 3mm and a minimum thickness of six layers."
Of the three different sourcing types, chemical, mechanical and electromechanical, he puts forward that the latter is
the preferred option. Using applied voltage to force apart the
graphite layers creates a source of high-quality feedstock for
volume exfoliation of graphene platelets. These are suitable
for use in many commercial applications, including plastics
and elastomers.
First Graphene has delivered materials for a series of
commercial projects, including wear liners used in mining
operations and industrial safety boots. In both instances, the
graphene has delivered a stronger, more durable product,
helping to improve performance and worker safety.

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Plastics & Rubber World - November/December 2019

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