Michael Kessler (left) and former Iowa State doctoral
student Will Goertzen use a dynamic mechanical analyzer to
measure the mechanical properties of polymers (Photo: Michael
Kessler)
Materials that can repair themselves are generally a good
thing, as they increase the lifespan of products created from
them, and reduce the need for maintenance. Biorenewable polymers
are also pretty likable, as they reduce or even eliminate the
need for petroleum products in plastic production, replacing
them with plant-derived substances. Michael Kessler, an Iowa
State University associate professor of materials science and
engineering, and an associate of the U.S. Department of Energy’s
Ames Laboratory, is now attempting to combine the two.
Self-healing materials generally incorporate microcapsules
containing a liquid healing agent, and catalyst elements, which
are embedded within the material’s matrix. As cracks form within
the matrix, the microcapsules rupture, releasing the healing
agent. As soon as that agent encounters the catalyst, it hardens
into three-dimensional polymer chains, thus filling and securing
the cracks. Such technology has been used not only to create
self-healing plastics, but also
self-healing concrete.
Since 2005, Kessler has been working with
Iowa State’s
Prof. Richard Larock on the development of biorenewable polymers
made from vegetable oils. Larock is the inventor of a process
wherein bioplastics can be created that consist of 40 to 80
percent inexpensive natural oils – these plastics reportedly
have very good thermal and mechanical properties, are good at
dampening noises and vibrations, and are also very good at
returning to their original shape when heated.
Kessler is now trying to create self-healing versions of
these same plastics.
One thing he has deduced so far is that a healing agent for a
tung oil-based polymer works too fast. Kessler and his
colleagues are now working on slowing down the reactive process
of that agent, while also developing biopolymer-friendly
encapsulating techniques, and bio-based healing agents.
The big challenge, he says, is to match the 90 percent
healing efficiency of standard synthetic composites.
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