How exactly do vinyl "static" clings work?

Question

My son asked me this question today, and for the life of me, I can't come up with a good answer that even convinces myself.

Vinyl "static" clings are those decorative pieces of vinyl that you can stick onto the inside surface of car windshields, windows etc. They require no adhesive (nor are they made with adhesive on their surface).

One website states they work by static electricity, which sounds plausible until you come upon another website that asks the question: if they worked by static, how is it that the vinyl can easily be folded over itself and get stuck in that position? Surely the charges on that surface of the vinyl are like and should repel? Also, these vinyl clings will stick just fine to conductive metal, which shouldn't happen if the effect is mediated by static electricity.

The problem is that no site actually seems to provide an explanation that satisfies us both. Some talk about the smooth vinyl causing "cohesive forces", and others talk about imagining thousands of "suction cups" on the surface, but clearly neither of these are adequate or precise enough to explain what's going on.

One of the sites likened the vinyl clings to plastic cling wrap, which also sticks to itself, so I guess the same mechanism also causes adhesion in this situation. Similar situations that might be explained by the same phenomenon include the way smooth glass tiles tend to stick together, but I don't know if these are all governed by the same principle.

Could someone please tell me what exactly is causing the stickiness in these instances? - vinyl on glass, plastic cling wrap on glass and other things and smooth glass on smooth glass.

At a microscopic level, I believe some form of electrical force is definitely at play. But it doesn't seem to behave like I have come to expect of "static electricity" on the macroscopic scale. Please help. Thank you.

Answer 1

Finding "how it works" pages turns out to be rather difficult indeed. Here is one explanation from a college physics dept Q&A page.

"Surface-to-surface adhesion" is just a fancy name for things sticking together, so it doesn't tell you much beyond what you were asking. The main mechanism is probably vanderWaals forces between the surfaces. These are the sort of forces that tend to make all sorts of different materials stick to themselves and each other. They involve the electric charges in the material doing a sort of coordinated dance, so that even though both pieces are neutral the positives in one tend to be close to the negatives in the other at any time. This generic mechanism is sure to be present.