Self-repairing mechanism of plastics

The protection mechanism of a living body and man-made materials can be classified into two categories. One is a passive protection by which the body and materials are guarded by simple chemicals such as light absorbents, and the other is an active protection that repairs with metabolic reactions the internal injury suffered by many kinds of deterioration factors from the outside. Polyphenylene-ether was selected as a man-made material in which the metabolic reaction can be achieved in the atmosphere (21% of oxygen) and at room temperature (20-40 degrees C). The polymer introduces oxygen as an energy source, transports it with copper-complex and repairs the scission point of the chain. Such active protections were attempted for several polymers and some advantages and problems were elucidated. In this paper, the mechanisms of active protections in some plastics are reviewed and are also compared with protection systems of a living body, which provide us with very useful information on the development of advanced materials. (C) 2003 Elsevier Ltd. All rights reserved.