Whats makes glue stick

Answer 1

Oddly enough, glue only sticks due to the effects of friction. Friction is simply a function of the normal force of the object against another surface and a frictional force constant, m. m (greek, actually "mu") is determined by the way that the two surfaces interact when they touch. Imagine sliding two smooth boards past each other. Now imagine sliding two pieces of sandpaper past each other. It's a function of the bumps, because the bumps get in the way. Having glue in between two surfaces links the bumps together like puzzle pieces link together, thus creating an "infinite" frictional force constant. You can only separate the two by overcoming the shear force necessary to break the "links" between the "puzzle pieces".