What follows is a more technical explanation than just about anyone could ever need, but here at Joint Specialists, we believe in teaching whenever possible, so here goes:
Once upon a time, it was discovered that the exposure of some plastic materials to high energy penetrating radiation can, in some cases, cause the permanent crosslinking, or intermolecular joining, of adjacent molecules. This crosslinking results in the chemical bonding of the plastic structure into a new three dimensional network. In addition, those plastics also no longer 'melt' as a typical plastic will AND those plastics gain a superior level of abrasion resistance over non-crosslinked materials.
|Thermoplastic materials on a molecular level|
|Thermoplastic material on a molecular level after crosslinking|
The unique heat-shrinkable properties of Covalence (and Raychem) products result from the exposure of a special thermoplastic formulations to radiation. Because of the resulting crosslinking, Covalence products have perfect elastic memory. These products are supplied in a deformed or expanded condition. When heated, they will shrink and tightly cover the object over which they have been placed. They are ideal for covering a variety of pipeline, electrical, and electronics components.
|Enlarged schematic view of a very small crosslinked section of extremely long molecules|
|Molecule currently heated above its crystalline melt point|
|Tubing is expanded / stretched|
|Shrink sleeve molecular structure as supplied|
|Shrink sleeve molecular structure 'in melt' or - during installation|
|Upon cooling, crystals reform|
And now, whether you are coating the field joint of a pipeline; sealing some some kind of electrical splice or coating ten miles of pipeline at a factory; thanks to radiation chemistry your substrate is now confidently "Sealed for Life!"