Michael Kessler, left, and former Iowa State doctoral student Will Goertzen use a dynamic mechanical analyzer to measure the mechanical properties of polymers.
Michael Kessler has worked with polymers that repair
themselves when they crack. And he’s worked with polymers made from vegetable
oils. Now he’s working to combine the two technologies.
Kessler, an Iowa State Univ. associate professor of
materials science and engineering and an associate of the U.S. Department of
Energy’s Ames Laboratory, is researching and developing biorenewable polymers
capable of healing themselves as they degrade and crack.
“If successful, the results of this research will
provide biorenewable alternatives to petroleum-based resins,” says a
summary of Kessler’s research project. Successfully developing the concept
“should have a huge impact economically and environmentally.”
Kessler’s research project is supported by a five-year,
$400,000 grant from the National Science Foundation’s Faculty Early Career
Kessler started working with self-healing materials as a doctoral
student at the Univ.
of Illinois at
Urbana-Champaign. He was part of a research team that in February 2001
published an article in the journal Nature that helped launch the field.
The technology has evolved into a system that embeds
catalysts and microcapsules containing a liquid healing agent within a composite.
As cracks develop in the composite, they rupture the microcapsules and release
the healing agent. The healing agent contacts the catalyst and reacts by
forming 3D polymer chains that fill the cracks. That increases material lifetimes
and reduces maintenance.
Visit his office, and Kessler will pull out a little
container half filled with what looks like fine yellow powder. Those are the
hollow microcapsules that make the self-healing process work, he said. (They’re
also the same technology behind scratch-and-sniff perfume ads.)
When Kessler joined Iowa State
and the Ames Laboratory in 2005, he started working with Richard Larock, a
Distinguished Professor of Chemistry and associate of the Ames Laboratory, to
develop biorenewable polymers from vegetable oils.
Larock has invented and patented a process for producing
various bioplastics from inexpensive natural oils, which make up 40% to 80% of
the plastics. Larock has said the plastics have excellent thermal and
mechanical properties and are very good at dampening noises and vibrations.
They’re also very good at returning to their original shapes when they’re
But can they be developed into a self-healing material?
Early results show there’s laboratory work to do. Kessler’s
research has found that a healing agent for a polymer based on tung oil works
too fast. Kessler and Peter Hondred, an Iowa State
graduate student in materials science and engineering, are working to slow the
agent for better healing.
The researchers are also working to develop encapsulating
techniques that work with biorenewable polymers. And they’re working to develop
bio-based healing agents.
Despite the challenges, Kessler thinks there is potential to
develop self-healing, biorenewable materials. He said the big question is whether
researchers can push the healing efficiency of biorenewable polymers close to
the 90% of standard composites.