Tuneable bioplastics
Plastics pose a problem for the planet – from the fossil fuels used to produce them to the harmful
chemicals released during their slow degradation. But plastic is so ubiquitous that giving it up
presents a complex challenge.
Winter 2019 www.materialsforengineering.co.uk
PLASTICS
Plastic has become such an integral part of
life in the Western world that it’s often
easy to forget that the material was only
invented in the 19th century. This is just as well,
as many of the durable plastics in single-use
products, such as bottled water and six-pack
rings, can take up to 450 years to degrade.
Today, we could probably nd remnants of the
rst plastics ever manufactured still laying in
land ll or oating in our oceans.
The longevity of plastics wouldn’t be as acute
a problem if it weren’t for the scale of their use.
Polymers are remarkably versatile materials,
boasting wide-ranging characteristics from
durability and sti ness to tensile strength and
exibility, depending on the speci c polymer
used. This versatility means plastics feature
everywhere from structural reinforcement to
disposable packaging.
In March 2019, the Ellen MacArthur
Foundation published its New Plastics
Economy report, which noted that 8 million
tonnes of plastic packaging is produced every
year by 30 global brands. Almost 50% of
this packaging was produced by Coca Cola,
totalling three million tonnes. Much of this
packaging will be single use, so the majority of
the eight million tonnes produced this year will
be plastic pollution next year.
The problem goes
much further than just a
build-up of waste plastic
cluttering the land and
sea. Because plastic is a
man-made material, it
is generally di cult to
break down naturally.
For most naturally
occurring materials,
decomposition occurs
According to
fi gures published
in Science in 2015,
anywhere between
4.8 and 12.7 million
tonnes of plastic fi nds
larger material and break it down into
smaller, useful compounds.
Breaking the chain
Unless they are recycled or incinerated, plastic
products that are discarded end up in one of
two places. They are either disposed of with
general waste and destined to reside in land ll,
or are thrown away as litter, which can then
wind up in the oceans. According to gures
published in Science in 2015, anywhere between
4.8 and 12.7 million tonnes of plastic nds its
way to sea every year.
“For the tonnes of plastic that are washed
away into the ocean, ultraviolet radiation
from the sun is the main factor in uencing
degradation,” explains Dr Ashlee Jahnke,
“The decomposition
process of plastic
involves the long,
the linkages holding the atoms of the
material together break.”
Although it can take
more than 450 years for
plastic to fully degrade,
the process of chain
scission happens at a
much faster rate, with
the rst chains breaking
in under one year.
In our oceans,
this poses two
fundamental
problems. The
rst is that the
smaller the
polymer
because bacteria consume the
director of research at
renewable polymer
producer Teysha
Technologies (pictured).
complex polymer chains
of the material being
separated into smaller
chains through a process
known as chain scission, whereby
its way to sea
every year
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