Page 73 - Plastics News October 2024
P. 73
PRODUCT NEWS
Researchers break down and rebuild PET and PP
packs in new chemical process
value plastic, the university says.
“We have an enormous amount of polyethylene
and polypropylene in everyday objects, from
lunch bags to laundry soap bottles to milk jugs
— so much of what’s around us is made of these
polyolefins,” said research leader and UC Berke-
ley professor of chemistry John Hartwig. “What
we can now do, in principle, is take those objects
and bring them back to the starting monomer
by chemical reactions we’ve devised that cleave
the typically stable carbon-carbon bonds.
“By doing so, we’ve come closer than anyone to
give the same kind of circularity to polyethylene
and polypropylene that you have for polyesters
At the University of California, Berke- in water bottles.”
ley, a new chemical process claims to
Hartwig and his team previously conceptual-
‘essentially vaporize’ polyethylene,
ized a depolymerization process for plastic bags
polypropylene, and mixed-plastic
made of polyethylene. This broke them down
waste into building blocks for repo-
into propylene (or propene) monomers, which
lymerization into new plastics.
could then be reconstructed into polypropylene
plastics.
f scaled up, this catalytic process is set to re-
Three different heavy metal catalysts were uti-
duce the fossil fuels required to make new
lized. Onen added a carbon-carbon double bond
Iplastics and unlock circularity for various sin-
to the polyethylene monomer, at which point the
gle-use plastics – including clear PET water bot-
other two would break the chain and cut off a
tles, which the university says were designed for
carbon atom. This atom would react with ethyl-
circular recycling processes.
ene to produce propylene in a repeated process
Around two-thirds of post-consumer plastic that continued until the polymer disappeared.
generated worldwide is thought to be made of
However, because the catalysts were soluble
polyethylene and polypropylene. Approximately
and would dissolve in the liquid reaction, it was
80% of it is believed to end up in landfills, incin-
difficult to recover them in an active form. The
eration, or the natural environment, leading to
new process implements cheaper solid catalysts
the leakage of microplastics into streams and
that are commonly used in the chemical industry
oceans. The remainder is downcycled into low-
for continuous flow processes; this means they
October 2024 PLASTICS NEWS 73
