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.