Why is the cling film sticky?

In daily life, we often need to use plastic wrap, which can attach to various foods and tableware, and sometimes even shrink into a ball. In fact, the stickiness of fresh-keeping film comes from two aspects: electrostatic force and molecular structure.

Most cling films are made of polyvinyl chloride or low-density polyethylene, both of which are long chain molecular polymers. The long chains coiled together can be stretched, allowing the cling film to be placed on a plate or bowl. In addition, when you unfold the cling film, the electrons on its surface will separate between adjacent layers, causing one side to have a positive charge and the other side to have a negative charge. Due to the fact that plastic wrap itself is a good insulator, static electricity will remain for a long time, and they will adhere to objects with opposite charges, such as many plastic bowls with slight negative charges on the surface.