The stretchable cling film is particularly practical for storing opened food or fruit. Where does its ability to stick to its surroundings come from, and why do some surfaces stick better than others?
By packaging the food hermetically, the cling film helps to protect and protect itstarted. One of the phenomena associated with its adhesive power is related to it of the same kind as the brush that “attracts” the hair, or the discharge that we sometimes feel when we take off a sweater.
When unrolling the hoseare torn from the surface of the which is therefore positively charged, lost negative charges. Stretch film is relatively good , it holds the charge for some time. Some materials such as glass are negatively charged, the two opposite charges attract each other, causing the film to stick.
Cling film doesn’t really stick… but it stretches
However, static electricity is not enough to explain adhesion, especially since theAlso “sticks” to conductive materials such as or wet surfaces that are designed to distribute electrical charges and thus eliminate the charge difference. This adhesive force results in particular from the molecular structure of the .
thatis made of polychloride ( ), polyvinylidene chloride (PVDC) or low density (PEDB) that have long chains tightly tied and rolled up. This configuration gives it its highly extensible character (up to 200%) and allows it to be wrapped around containers.
To make their film even more “sticky”, manufacturers often add an additive (monooleate or polyisobutylene) at 0.5 or 2.5%. However, the stretch film tends to shrink after a few days, leading to loss of adhesion. Ironically, Cellofrais adheres much better to its own roller tube than to other surfaces!