Wednesday, April 15, 2009

Self-Healing Polymers

Self Healing Polymers and Coatings are beginning to pick up speed. Not only are there a number of papers (this one by Braun being the latest) , but there are multiple academic groups (1, 2, 3, 4, and 5) specializing in the research, a couple of patents (1 and 2) using the materials.

The most common thread in all these materials is that there is a reactive system encapsulated within a microbead, and these beads are spread throughout the rest of the polymer matrix. When the matrix is fractured, the beads adjacent to the break are fractured, leaking out their reactive material which then (ideally) fills the void and sets up as a solid.

The real challenge behind the hype is achieving a good bond between the matrix and the reacted material. Given the extremely uncommon compatibility of binary polymers systems, such a bond is unlikely. And even in systems that are compatible, obtained an interdiffused interface is impossible given the solid nature of the matrix.

If all you seek is a protective coating, that might be enough for a while, but eventually the environment will succeed in finding the weak spot and exploiting it. That's just the way that Mother Nature works.

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