Page 58 - Plastics News June 2018

teChnoLogy

'Infinitely' recyclable polymer shows practical properties of plastics

olorado State University chemists have announced in gained from that study was invaluable, Chen said. It led
Cthe journal Science another major step toward waste- to a design principle for developing future-generation
free, sustainable materials that could one day compete polymers that not only are chemically recyclable, but also
with conventional plastics. Led by Eugene Chen, professor exhibit robust practical properties.
in the Department of Chemistry, they have discovered The new, much-improved polymer structure resolves the
a polymer with many of the same characteristics we issues of the first-generation material. The monomer
enjoy in plastics, such as light weight, heat resistance, can be conveniently polymerized under environmentally
strength and durability. But the new polymer, unlike friendly, industrially realistic conditions: solvent-free, at
typical petroleum plastics, can be converted back to
room temperature, with just a few minutes of reaction
time and only a trace amount of catalyst. The
resulting material has a high molecular weight,
thermal stability and crystallinity, and mechanical
properties that perform very much like a plastic.
Most importantly, the polymer can be recycled back
to its original, monomeric state under mild lab
conditions, using a catalyst. Without need for further
purification, the monomer can be re-polymerized,
thus establishing what Chen calls a circular materials
life cycle. This piece of innovative chemistry has Chen
and his colleagues excited for a future in which new,
green plastics, rather than surviving in landfills and
oceans for millions of years, can be simply placed in
a reactor and, in chemical parlance, de-polymerized
to recover their value -- not possible for today's
petroleum plastics. Back at its chemical starting
point, the material could be used over and over again
-- completely redefining what it means to "recycle."

"The polymers can be chemically recycled and reused,
in principle, infinitely," Chen said.Chen stresses that
the new polymer technology has only been demonstrated
its original small-molecule state for complete chemical at the academic lab scale. There is still much work to be
recyclability. This can be accomplished without the use of
toxic chemicals or intensive lab procedures.Polymers are done to perfect the patent-pending monomer and polymer
production processes he and colleagues have invented.
a broad class of materials characterized by long chains
of chemically bonded, repeating molecular units called With the help of a seed grant from CSU Ventures, the
chemists are optimizing their monomer synthesis process
monomers. Synthetic polymers today include plastics,
as well as fibers, ceramics, rubbers, coatings, and many and developing, new, even more cost-effective routes to
other commercial products.The work builds on a previous such polymers.
generation of a chemically recyclable polymer Chen's lab They're also working on scalability issues on their
first demonstrated in 2015. Making the old version required monomer-polymer-monomer recycling setup, while
extremely cold conditions that would have limited its further researching new chemical structures for even
industrial potential. The previous polymer also had low better recyclable materials."It would be our dream to see
heat resistance and molecular weight, and, while plastic- this chemically recyclable polymer technology materialize
like, was relatively soft.But the fundamental knowledge in the marketplace," Chen said.

Plastics News June 2018 58