Thank you Banbocan, Sweeney,
The mentioned article of Wikipedia is not very informative, I am afraid.
Depending on the material used, there are two ways that heat shrink may work.
1. If the material contains many monomers, the monomers polymerise when the tubing is heated. This increases the density of the material as the monomers become bonded together, therefore taking up less space. Accordingly, the volume of the material shrinks.[citation needed]
2. Heat shrink can also be expansion-based. This process involves producing normal tubing, then heating it to just above the polymer's crystalline melting point and mechanically stretching the tubing (often by inflating it with a gas); finally, it is rapidly cooled. Later, when heated, the tubing relaxes back to its un-expanded size. The second process is what I had in mind : It involves melting, mechanical expansion, rapid cooling that stabilizes the molecular structure of the material at the expanded size / stage, and then heating to "revitalize" the stress "memory" of the material, and so allow it to retain to its original size. It works like a one-piece hose clamp.
The first process is also a kind of melting, at a molecular scale. Heat is used to induce a chemical transformation of the molecular structure of the material, the polymerization, which changes the shape of the molecules, and thus their size. I believe this is a one-off process, because I do not see how those polymerized polymers can possibly return to their initial form. Citation needed !
With all respect, I think that both procedures are not very different from
gluing !
I belong to an other era, where when one needed to join two pieces of material together, he used nuts and bolts, dovetails, mortices and tenons, and all that. So, I guess I will never characterize the method of joining two things together by using glue, as "elegant ".
Most knots, if not all of them, will become permanent and super-strong, if we immerse them in a contemporary strong glue... I am not ready to propose
this to a knot tyer ! Also, if the cost of rope becomes more negligible, one would possibly prefer to glue the ropes together, and then just to cut-off the joined segments, or buy new ropes. "
Gluing and cutting-off" would become the method of choice, and the word "
knot" will be forgotten. Fortunately, I will not live to see this day !