there is a technical treat ment named cross linking, the process of cross-linking is exposing a polymer to radiation in order to create covalent bonds between that polymer's atoms. it was discovered that radiation was capable of altering the molecular structure of certain plastics so that they wouldn't melt or develop a flowing consistency, no matter what temperatures they were exposed to. Covalent bonds also give polymers plastic memory, which means that once a polymer has been cross-linked and stretched into an expanded shape, it will automatically shrink back to its original dimensions when a certain amount of heat is applied.
Where to find heat shrink tubing
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