There are a lot of forces at work but mostly chemical, both covalent and
ionic.

Mechanical is also important as glue might penetrate when it is liquid.

The mechanical properties of the glue are also important particularly
when bonding materials with considerably different mechanical properties.

Not a simple subject and I worked in the area in R&D for several years.

On 9/17/2017 3:21 PM, Mad Roger wrote:
What is the chemical force that makes common household glues work

Very few are solvents such as the pipe-fitting "glues" which actually melt
(weld) the plastic together.

Most are some kind of "bonding", where some glues are strong themselves,
like Elmers Glue but while others are extremely weak in and of themelves,
like Cyanacrylate crazy glue - but what kind of bonding is glue?

Looking at the Shoe Goo MSDS, it's toluene based but that's all I can get
out of the MSDS. The toluene is the solvent which seems to vaporize,
leaving the "glue" behind mechanically wedged into all the molecular
crevices. http://www.bild.me/bild.php?file=6713513goop02.jpg

I know about covalent and ionic bonding and the nuclear strong and weak
forces, but common household glue doesn't seem to be any of those forces.

Common household glues seem to be some kind of strange "mechanical"
molecular cantilevered arm that "solidifies" and somehow mechanically holds
things together.

Do any chemists out there know what "force" is what holds most common glues
to their substrates?

I call it the "velcro force" because it's none of the common forces.
But what is it really?