How polyethylene is made
The most-made plastic was found by accident in 1933, when ICI chemists squeezed ethylene hard and got white wax.
- stations
- 6
- things upstream
- 6
- raw sources
- 3
- steps from the ground
- 4
The short version
Polyethylene is made by linking ethylene molecules into very long chains, using a catalyst or a high-pressure reactor. The result is a powder or molten plastic. It is melted, mixed with additives, pushed through a die and chopped into small pellets, which other factories turn into bags, bottles, pipe and film.
-
Purify the ethylene
Ethylene gas is cleaned of moisture and traces of other compounds. Impurities would kill the catalyst and cut the chain length of the polymer.
Goes in -
Link the molecules in a reactor
Inside a reactor, thousands of ethylene molecules join into long chains. A Ziegler-Natta, chromium or metallocene catalyst, or a high-pressure free-radical process, sets the chain structure and so the type of plastic.
-
Separate the polymer
Unreacted gas and solvent are flashed off and recycled. What is left is a powder or a molten polymer.
-
Melt and mix in additives
An extruder melts the polymer and blends in antioxidants, color and other additives. The mix is pushed through a die plate with many small holes.
-
Chop it into pellets
Rotating blades slice the strands at the die into small pellets under water. The pellets are dried and sorted by size.
-
Bag and ship the resin
Pellets are blown into silos, bags or rail hopper cars. Film plants, bottle makers and pipe extruders buy them by the truckload.
Worth repeating
- Polyethylene is the most commonly produced plastic, with over 100 million tonnes of resin made each year as of 2017.
- Its low loss to radio waves led Britain to suppress commercial sales at the start of World War II and use it to insulate the cables of radar sets.
- Its chemical resilience makes it long-lasting but also a decomposition-resistant pollutant when it is thrown away carelessly.
Back to the ground
Follow every input upstream and polyethylene starts as these 3 raw sources.
Everything it is made of See it on the map
Open the whole family tree
Where it goes next
Polyethylene feeds 23 lines directly and reaches 188 things in total.
Further down the line
Keep walking
Sources
Cite this page: "How polyethylene is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/polyethylene