Page 64 - Plastics News November 2019

teChnoLogy

What makes it now feasible to use collected and sorted quality plastics. The Chalmers researchers therefore see an
plastics in large-scale petrochemical plants is that a opportunity to create a circular use of plastic in society,
sufficient volume of material is collected, meaning that the as well as free us from the need for oil and fossil gas to
plants can theoretically maintain the same output. These produce various high-quality plastics. "Circular use would
plants require around 1-2 million tonnes of sorted plastic help give used plastics a true value, and thus an economic
waste per year to convert to match the production levels impetus for collecting it anywhere on earth. In turn, this
they currently derive from oil and fossil gas. Sweden's total would help minimise release of plastic into nature, and
amount of plastic waste in 2017 was around 1.6 million create a market for collection of plastic that has already
tonnes. Only around 8 percent of that was recycled to lower polluted the natural environment, says Henrik Thunman.

Tubulanes inspire ultrahard polymers

esearchers at Rice University's Brown School of in the solid block, cracks propagated through the whole
REngineering and their colleagues are testing polymers structure."Tests in a lab press showed how the porous
based on tubulanes, theoretical structures of crosslinked polymer lattice lets tubulane blocks collapse in upon
carbon nanotubes predicted to have extraordinary themselves without cracking, Sajadi said.The Ajayan group
strength. The Rice lab of materials scientist Pulickel made similar structures two years ago when it converted
Ajayan found tubulanes can be mimicked as scaled-up, theoretical models of schwarzites into 3D-printed blocks.
3D-printed polymer blocks that prove to be better at But the new work is a step toward what materials scientists
deflecting projectiles than the same material without consider a holy grail, Sajadi said. "There are plenty of
holes. The blocks are also highly compressible without theoretical systems people cannot synthesize," he said.
breaking apart. A lightweight material full of holes "They've remained impractical and elusive. But with 3D
is nearly as hard as diamond. The mere dents left by printing, we can still take advantage of the predicted
speeding bullets prove it. Rice graduate student and lead mechanical properties because they're the result of the
author Seyed Mohammad Sajadi and his colleagues built topology, not the size." Sajadi said tubulane-like structures
computer simulations of various tubulane blocks, printed of metal, ceramic and polymer are only limited by the
the designs as macroscale polymers and subjected them size of the printer. Optimizing the lattice design could
to crushing forces and speeding bullets. The best proved lead to better materials for civil, aerospace, automotive,
10 times better at stopping a bullet than a solid block of sports, packaging and biomedical applications, he said.
"The unique properties of such structures comes from their
complex topology, which is scale-independent," said Rice
alumnus Chandra Sekhar Tiwary, co-principal investigator
on the project and now an assistant professor at the Indian
Institute of Technology, Kharagpur. "Topology-controlled
strengthening or improving load-bearing capability
can be useful for other structural designs as well."
According to co-authors Peter Boul and Carl Thaemlitz
of Aramco Services Co., a sponsor of the research,
potential applications span many industries, but oil and
gas will find tubulane structures particularly valuable
as tough and durable materials for well construction.
the same material. The Rice team fired projectiles into Such materials must withstand impacts, particularly in
patterned and solid cubes at 5.8 kilometers per second. hydraulic fracturing, that can rubblize standard cements.
Sajadi said the results were impressive. "The bullet was "The impact resistance of these 3D-printed structures puts
stuck in the second layer of the structure," he said. "But them in a class of their own," Boul said.

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