| MadSci Network: Chemistry |
Methinks you are confusing adhesive "bonding" with chemical bonding.
There is no chemical bond formed. What happens is that (in the case of
Elmer's glue and similar latex glues) the polymer + solvent fills in the
surface pores (which is why they work best with porous materials). Then the
solvent evaporates, leaving behind a polymer film which adheres to itself
in the same way that strands of cooked spaghetti adhere to each other. The
whole thing acts as a glue because the polymer has penetrated pores in
the surface of each object, and when it hardens it doesn't want to come out!
Think about paint, which has the same sort of polymer in it: have you
ever "glued" something together with paint? painted a door or window
shut? doesn't paint get "tacky" as it dries?
(Incidentally, that's how they get teflon to stick to frying pans: they
sandblast the metal surface, then coat it with they polymer. When it dries,
the polymer has penetrated the surface and doesn't want to come out.)
Other types of adhesives (epoxies and cyanoacrylates, for example) form
the polymer in situ; this gives them greater penetrating power, because
the small molecules can penetrate smaller pores before they link up
into the polymer network.
But in no case do you ever get a chemical bond between glue and
substrate.
Dan Berger, Admin MadSci Network
Try the links in the MadSci Library for more information on Chemistry.