How are plastic bags made?

For example, if you want to make a  bag, you need to buy a high density plastic (HDPE).

Other examples of products using HDPE include bottle boxes, milk cans and outdoor plastic chairs that you often see at children's birthday parties.

Step 1 – Plastic film extrusion

The process of plastic bag production looks pretty strange.

Raw plastic pellets (known as nurdles) of different densities (such as, HDPE, LDPE, or LLDPE) are again super heated and pressurized to form a molten liquid, which air is then pumped into from below.

As this plastic bubble expands upwards it cools, coming into contact with many rollers that stretch and contort the plastic into thin film sheets.

Several hundred meters of these sheets then roll onto two separate cylinders.

These condensed rolls of plastic are then moved off to the printing department.

Step 2 – Printing on the plastic bags

Most single-use plastic bags consist almost entirely of pure polyethylene molecules.

However, the plastic bags you get at most shopping malls and supermarkets usually have some sort of color print on them.

The process of printing on super sensitive/light material such as plastic bags is called flexographic printing.

Step 3– Completing the manufacturing process

Finally, the two printed sheets are then pressed together at the edges, effectively sealing the bag.  

The sealed plastic bag can then be cut to desired sizes, depending on the commercial intent for the bag.

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