Eli5: What makes things “sticky” like tape or any kind of adhesive? How do they stick on to smooth surfaces instead of coming off?
In: Chemistry
So adhesive on tape sort of turns into a liquid, then it flows into the nooks and crannies of the thing you’re sticking it to, then it sort of turns back solid again and then hangs on to the thing you’re sticking it to like legos.
There’s two primary forces going on here. The first is pretty easy to visualize. The adhesive on tape is what you call viscoelastic, meaning it behaves sort of like a liquid even though it’s solid, and it’s stretchy. So it “flows” into all the oils and crannies of a surface then hangs on tight. A surface may look smooth to you, but chances are it has many pits and pores and mountains under a microscope.
The second is a little harder to visualize. All molecules are made of atoms which have electrons, which are negatively charged, and protons, which are positively charged. If an atom has the same number of electrons and protons, it is neutrally charged overall. Some neutral molecules still are negatively charged on one side and positively charged on another side, because some atoms in the molecule are greedy for electrons and pull the electrons in tight. So in these molecules, like the ones in tape adhesive, you get positive parts where the electrons went away and negative parts where the electrons got pulled in tight. Positive likes negative and sticks to it like legos, and the adhesive on tape similarly behaves almost like legos like with the surface of the material you stick it to.
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