Please note that the content of this book mainly consists of articles that are available for free online from Wikipedia or other sources. Adhesive films are soft, very smooth plastic films made of PVC or PE that adhere to smooth surfaces without glue. This adhesion is caused by loose molecular bonds (Van der Waals forces) between the boundary layers of the film and the material it is in contact with. For these weak forces to have a noticeable effect, the contact area must be as large as possible, which is only the case with truly smooth surfaces like those of glass, porcelain, polished metal, and some plastics. By wrapping around itself multiple times, it adheres to itself.