Tech Briefs Magazine - October 2021 - 12

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Tech Briefs: What is upcycling of
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Professor Aaron Sadow: Once the lifetime
for materials' intended application
has been exhausted, you have to decide
what to do with them - in this case,
plastics. One approach might be to recycle
them, which in principle could be
done mechanically. In most instances,
though, the plastics that you would get
are of lower quality or almost no value
compared to the original material. Our
idea is to instead use chemistry and
transform them into equal or better
higher-value materials - that's upcycling.
If you could pay for this with the
higher value of the product you're making,
that would incentivize the process.
Tech Briefs: Could you describe the
process?
Sadow: The plastics we're targeting
are polyolefin-based polyethylene. An ex -
ample is the high-density polyethylene
used in milk containers and grocery
bags because it's strong and has a high
melting point. These plastics are all
composed of hydrogen and carbon -
long carbon chains. We use a catalyst to
break selected bonds holding those
chains together so that the carbons are
no longer thousands of carbon atoms
linked together in a long sequence but
instead, 20 to 40 carbons. The key is figuring
out how to turn those very long
chains into carbons that can be used for
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Who's Who
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Plastics Could See Second Life as
Biodegradable Surfactants
Professor Aaron Sadow
of Ames Laboratory in
Iowa is director of the In -
stitute for Cooperative
Up cycling of Plastics
(iCOUP). The Institute
has developed a chemical
process that produces valuable bio -
degradable chemicals from discarded
plastics, which are then used as surfactants
and detergents in a range of applications.
other
applications. Chains 40 carbons
long might be a lubricant, for example.
Tech Briefs: Do you add heat or
pressure?
Sadow: We melt the plastic and add a
catalyst. We've been studying platinum
nanoparticle-based catalysts but there
are other catalysts you can use. That's
really the basic research question: what's
the nature of the catalyst? How does the
catalyst function to do this kind of
process in an efficient manner at the
lowest temperature possible, under the
mildest conditions, so that it's efficient
and low cost?
So, we take the catalyst and melted
polymer and add hydrogen - around
100 psi or so. This mixture is allowed to
react for between six hours and a few
days. When you're done, if the catalyst
has worked, you end up with waxy or liquid-like
hydrocarbon products.
Tech Briefs: In addition to the
economic benefits, there is a huge
environmental benefit, correct?
Sadow: Yes. We take a large amount of
our petroleum resources and make them
into fuels and then 10% goes to chemicals
- probably half of that goes into
plastic. That's a lot of petroleum. So,
using that resource more efficiently is
important for us for the future.
Plastics upcycling is a great first step to
thinking about how to make use of our
petroleum resources in a circular kind
of way. That's why I think there's really a
lot of discussion about a circular economy
for plastic.
There has long been interest in learning
how to recycle plastics more efficiently
than we currently do. Recently,
China stopped accepting American plastic
waste and it again became a visible
problem in the United States. I think
that that's the big change.
Read the full transcript of this Q&A at
www.techbriefs.com.
Tech Briefs, October 2021
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Tech Briefs Magazine - October 2021

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