Plastic bags are made out of polyethylene or polythene. Polythene is produced from crude oil and natural gas, two non-renewable resources found underground, through a process known as the tubular film process.
In this process, the polythene is molded to form a thin tube, where air is then injected inside to blow out a thin plastic-like sheet in the form of a bubble. A fan on top of the machine blows air on the created film to continuously cool the plastic and the tube is stretched out to create thin sheets. This can then be molded to create the shape of a plastic bag by a cutting and perforation process.