How Polythene films made?
Most polythene films are made out using blown film process. In the Blown Film Extrusion process, small plastic pellets (called resin) are melted down under controlled conditions so that they are pliable molten actually—and pressed (extruded) through a circular die gap to form a continuous tube of plastic. While it is still in this molten state, the tube is pinched off at one end, then it is inflated and stretched to the size and thickness of the desired finished product. The inflated bubble of plastic is drawn vertically up a tower so that it has a chance to cool before it is flattened out and wound onto a roll. The plastic pellets enter at one end of the machine and film is wound up at the other. This simple process can be used to make films that may be as thin as .0004 inch to thicknesses that may go beyond .01 inch. Sometimes pellets containing pigment are blended with the clear pellets to make film of various colours.
