Why do Plastic Layers Stick Together?
Most recent answer: 01/10/2015
- Michael Dawson-Bowman (age 20)
Static electricity is simple enough. Things can pick up a little electrical charge, usual by rubbing against some other surface, and if they pick up opposite charges they'll attract. This doesn't sound like a particularly likely reason for similar pieces of plastc to stick, since they'd typically pick up the same sign of charge, and thus repel. If somehow the plastic picked up patches of positive and of negative charge, then oppositely charged patches would find each other and stick. One way to test whether this sort of effect is important is to get a little hand-held piezo-electric ion gun and see whether spritzing ions at the plastic makes much difference for the stickiness.
"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.
I just grabbed one of those bags that tends to stick together off the roll at the store and rubbed it on my robe to give it some static charge. It now sticks to me like crazy, but once I shook it off the bag tends to stay open. The similarly charged sides do repel each other.
This may be a ridiculously complicated way to do things, but maybe using one of those piezo guns (they used to be sold to remove static from vinyl records) could be used to charge up the plastic sheets and help separate them. Or any little device that spits out ions might work.
(published on 01/10/2015)