Several years ago I bought a bunch of folders for about $1.00 each. Serrated blade, very, very sharp for a short time and who cares if you loose them.
I still have a couple of them and they are my favorite knife for one job I do.
I do volunteer work at a "gleaners" and cut tape and plastic film a lot.
The knife cuts the film but doesn't cut plastic bottles.
The first time I cut that type of film was with a nicer knife and I was in a bit of a hurry. The film and six bottles were sliced open and I didn't feel a thing.