A TECHNICAL PAPER ON THE IRRADIATION INDUCED ELASTIC MEMORY OF POLYMERS.
RAYCHEM CORP REDWOOD CITY CALIF
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One of the most interesting and novel applications has resulted from a study of the irradiation induced elastic memory of polymers. A typical example is the work that has been done with polyethylene. A most interesting feature of irradiated cross-linked polyethylene is that it behaves as a semi-crystalline polymer below its crystalline melting point, and as a rubber above its crystalline melting point, due to the irradiation induced three-dimensional gel network. It is possible to irradiate cross-link polyethylene in the solid state to form a three-dimensional gel network and then deform i.e. expand or contract polyethylene parts in the molten state. The deformation is accomplished because of the rubber-like extensibility and strength of the polymer when molten. It is then possible to freeze the particular part in the deformed state resulting in a stable configuration due to recrystallization of the polymer. This stable configuration will persist until the polymer is reheated to a temperature above its crystalline melting point, whereupon the polyethylene part will return to its original predetermined dimension. The unique combination of plastic-rubber-like properties permits one to use irradiated polyethylene in many and varied forms where crystalline melting through heat causes the polymer part to return precisely to its original cross-linked geometry. Author
- Radioactivity, Radioactive Wastes and Fission Products