Page 44 - Plastics News July 2020

University of Wisconsin plans to recycle plastic through pyrolysis

US-based University of Wisconsin Madison professor m o l e c u l a r - l e v e l
George Huber has announced plans to recycle plastic information about the
using pyrolysis process. Pyrolysis is a process that chemicals that you can
involves heating up the biomass in a low-oxygen make from pyrolysis.
environment in the presence of a catalyst. The process That gives us ideas
can break the plastic down into chemical feedstocks, about how we can more
and then recycle it into fuel or develop new virgin efficiently go back to
plastic. Huber said: “We started thinking about whether the original plastics.
we could pyrolyse those plastics and what we could The professor believes
make if we did that “We literally took our reactor, where that pyrolysis can be
we were pyrolysing biomass, and instead of adding wood used in recycling large
into the feed, we added plastic and made liquid oil. And bales of mixed plastics.
then we analysed the chemistry.” To study the possibility Recently, Huber and
of recycling plastics through this process, the research several colleagues
team melted down polyethylene, a plastic present in proposed a new multi-
shampoo bottles and grocery bags, at a temperature university research
ranging from 500 to 600 degrees Celsius. Huber, with the project called the
assistance of his graduate student Dongting Zhao, then Centre for Chemical Upcycling of Plastic Waste. The
analysed the liquid and gas products of that pyrolysis. centre will be used for studying and refining the plastic
Huber further added: “We're trying to provide more recycling process.

Making Plastic more transparent
In an effort to improve large touchscreens, LED light between them. "We developed a way to make coatings
panels and window-mounted infrared solar cells, with high transparency and conductivity, low haze,
researchers at the University of Michigan have made excellent flexibility, easy fabrication and great
plastic conductive while also making it more compatibility with different surfaces," said Jay Guo, U-M
transparent. They provide a recipe to help other professor of electrical engineering and computer
science, who led the work. Previously, Guo's team had
shown that it was possible to add a layer of metal onto a
plastic sheet to make it conductive -- a very thin layer of
silver that, by itself, reduced the transmission of light by
roughly 10%. Light transmission through plastic is a little
lower than through glass, but its transparency can be
improved with anti-reflection coatings. Guo and his
colleague Dong Liu, a visiting professor at U-M from
Nanjing University of Science and Technology, realized
that they could make an anti-reflection coating that was
also conductive. "It was taken for granted that the
transmittance of the conductor is lower than that of the
researchers find the best balance between conductivity substrate, but we show that this is not the case," said
and transparency by creating a three-layer anti- Chengang Ji, first author of the study in Nature
reflection surface. The conductive metal layer is Communications, who worked on the project as a Ph.D.
sandwiched between two "dielectric" materials that student in electrical and computer engineering. Ji
allow light to pass through easily. The dielectrics reduce received his doctorate from U-M in 2019.
the reflection from both the plastic and metal layer

July 2020 44 Plastics News