Page 46 - Plastics News May 2017

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that heat is evenly and non-abrasively dispersed and injection nozzles and die disks. At slightly longer cleaning
simultaneously decomposes the polymers adhering to times, it can remove plastics from spin nozzles and
the tool all while oxidizing the remaining carbon to leave assembled spin packs, static mixers, assembled pumps,
the tool free of residues. The parts are thereby cleansed back-flow preventers, hot runner components and many
of carbon and plastic with no mechanical or thermal other parts. InnovaClean INB-HT functions without any
deterioration and at polymer-dependent temperatures waste water and refuse. The generated carbonization
of up to 620 degrees Celsius. gases are cleaned with an integrated thermal afterburner
which can be optionally delivered with a waste-air washer
Within just one to two hours, the system is capable of for pyrolysis gases from PVC and PTFE.
the residue-free carbonizing of any polymer, e.g. from

Polymers with simple technique that cuts down on loops that

weaken plastics

lastic, rubber, and many other useful materials are “Just by changing how fast you add one component to the
Pmade of polymers — long chains arranged in a cross- other, you can improve the mechanical properties,” says
linked network. At the molecular level, these polymer Jeremiah A. Johnson, the Firmenich Career Development
networks contain structural flaws that weaken them. Associate Professor of Chemistry at MIT and the senior
Several years ago, MIT researchers were the first to author of the paper. MIT graduate student Yuwei Gu is the
measure certain types of these defects, called “loops,” first author of the paper, which appears in the Proceedings
which are caused when a chain in the polymer network of the National Academy of Science the week of April 24.
binds to itself instead of another chain. Now, the same Other authors are MIT associate professor of chemical
researchers have found a simple way to reduce the engineering Bradley Olsen; MIT graduate student Ken
number of loops in a polymer network and thus strengthen Kawamoto; former MIT postdocs Mingjiang Zhong and Mao
materials made from polymers. To achieve this, the Chen; Case Western Reserve University Assistant Professor
researchers simply add one of the components of the Michael Hore; Case Western Reserve graduate student Alex
polymer network very slowly to a large quantity of the Jordan; and former MIT visiting professor and Case Western
second component. Using this approach, they were able Reserve Associate Professor LaShanda Korley.
to cut the number of loops in half, in a variety of different In 2012, Johnson’s group devised the first way to measure
polymer network structures. This could offer an easy way the number of loops in a polymer network and validated
for manufacturers of industrially useful materials such as those results with theoretical predictions from Olsen. The
plastics or gels to strengthen their materials.
researchers found that the loops can make up about 9
percent to nearly 100 percent of the network, depending
on the concentration of polymer chains in the starting
material and other factors. A few years later, Johnson
and Olsen developed a way to calculate how much these
loops weaken a material. In their latest work, they set
out to reduce loop formation, and to achieve this without
changing the composition of the materials. “The goal we
set for ourselves was to take the same set of precursors
for a material that one would normally use, and, using
the exact same precursors under the same conditions and
at the same concentration, make a material with fewer
loops,” Johnson says.

Plastics News | May 2017 46