Self-Healing Plastic Changes Color When Damaged

A new type of thermoplastic can heal itself when exposed to light, temperature changes, or changes in pH, after first turning red to show that it's been damaged. The research was presented at a press conference at the 2012 National Meeting and Exposition of the American Chemical Society.

Marek W. Urban, professor at the University of Southern Mississippi, who led the research team that has made the discovery and reported its findings, said that the new co-polymer mimics the human skin's ability to heal scratches and cuts, and could offer the ability of self-repairing surfaces to cellphones, laptops, and cars.

Plastics can be difficult or impossible to repair once they've been scratched or cracked, yet they are now prevalent in many different products. The search for self-healing plastics has become more urgent as plastics have become ubiquitous in critical structures such as automobiles and aircraft, since damage can change a plastic's electrical, acoustical, and thermal characteristics.

Many types of self-repairing plastics mimic the abilities of biological systems. One method implants capsules into a plastic. When the plastic is scratched or cut, the capsules break open and release repair compounds that fix the damage. Another method depends on plastics that repair themselves by responding to specific outside stimuli, such as heat, light, or chemical agents.

While self-repairing plastics that depend on embedded healing compounds can only repair themselves once, Urban's plastic can repair itself many times. The process for producing the plastic is also water-based, making it more environmentally friendly and less expensive.

Other approaches include smart coatings, paint, or adhesives. These can be applied to the material and reveal damage when viewed at certain wavelengths, or signal damage by changes in electric current.