Garbage bags are made from low density polyethylene, which was invented in 1942.
Low density polyethylene is soft, stretchy, and water and air proof. Polyethylene is delivered in the form of small resin pellets or beads. By a process called extrusion, the hard beads are converted into bags of plastic.
The hard polyethylene beads are heated to a temperature of 200 degrees centigrade. The molten polyethylene is put under high pressure and mixed with agents that provide color and make the plastic pliable. The prepared plastic polyethylene is blown into one long tube of bagging, which is then cooled, collapsed, cut to the right individual length, and sealed on one end to make a garbage bag.