Page 24 - Plastics News March 2021

FeAtures

Researchers Combine Mechanical and Chemical Recycling

Researcher’s team is working on developing a novel hybrid chemical-mechanical technology for recycling
and upcycling of laminated and multilayered plastics.

hen there’s talk of team plans to develop a hybrid model, taking the low-cost
Wmechanical and chemical investment of mechanical recycling, but breaking down the
recycling, it’s usually an either- plastics through a new lower-temperature (about 350 C),
or situation. But researchers lower-pressure method.
at Case Western Reserve According to Maia, an important aspect is the use of
University, the private research a new twin-screw extrusion technology for continuous
university in Ohio U.S. are separation of materials in the melt and the modification
looking at combining aspects of current recycling technologies—catalytic cracking for
of both technologies into one PE and glycolysis and hydrolysis for PET—to extrusion.
hybrid chemical-mechanical Multi-scale computational modeling will be integrated
solution. with the chemical and processing studies to determine
With help from government and optimal catalytic and degradation routes, microstructure
industrial partners, the CWRU-led team are working to development and rheological behavior, and process kinetics
develop and test a technique that blends the high-efficacy and optimization.
chemical method of plastic recycling with the typically Maia says their process takes mixed waste, whether post-
high-output but low-efficacy mechanical recycling. industrial or post-consumer, after it’s been washed, and
puts it into an extruder and separates the materials in the
melt—such as polyolefins and polyesters each of which gets
upcycled separately.“The advantages are that it takes the
burden of sorting and separation away from the consumer,”
Maia says. “And hopefully we’ll be able to get the type of
scale from mechanical recycling and the type of quality of
upcycling from chemical recycling.”
Besides CWRU researchers and Braskem, partners in the
project include Procter & Gamble, Resource Material and
Recycling of Middlefield, Ohio, the Lawrence Livermore
National Laboratory, and Sandia National Laboratory. Grant
Goodrich, executive director of the Great Lakes Energy
“Mechanical is great for the volume that you need, but Institute at CWRU, which helped facilitate the research,
there are limitations on the end-value of the recyclate,” says the project could create novel solutions for two issues:
says the project’s lead researcher, João Maia, a professor addressing the difficult process of removing contaminants
in Macromolecular Science and Engineering. “Chemical (scraps of food, labels, etc.) from sorted plastic waste,
recycling helps to retain the value of the polymer, but the and recycling those plastics that have so far been difficult
problem is with scale.” The CWRU-led team will study how to recycle, such as laminated and multi-layered films and
to separate various polymers in the melt state, so that bottles.
each can then by upcycled by itself. One of the partners Maia said the initial research will be done at CWRU and then
in this work, Braskem, was able to separate about 20% of tested at a larger scale off-site. If this works, this can be
the PS from the plastic in trial runs. “But they did that an game changer. The team also will study how to separate
without optimizing the process,” Maia says. “We believe various polymers in the melt state, so that each can then
we can do that even better and achieve 80% separation. by upcycled by itself. The project was among a dozen
That would really move things forward, and it could be DOE-awarded grants totaling $27 million, a list that also
scalable so it could be handled by individual communities includes a $2 million award to the University of Akron, giving
with an investment as low as $3 million to $4 million.” The
Northeast Ohio nearly 17% of the total program funding.

Plastics News March 2021 24