How plastic straws are made

A plastic straw is a continuous tube of polypropylene chopped into lengths.

stations: 7
things upstream: 28
raw sources: 12
steps from the ground: 5

The short version

Polypropylene resin is melted together with color and stabilizers, cut into pellets, and fed to a second extruder fitted with a die shaped like a ring. The melt comes out as a continuous hollow tube. A puller draws it along, a water bath sets its shape, and a knife chops it into straws.

Blend resin and color

Polypropylene is mixed with colorants and additives that resist oxidation and sunlight. Only a small amount of pigment gives a bright, even color.

Goes in
Polypropylene Pigment
Pelletize the melt

The blend leaves the compounding barrel as thin strands, which are cooled and chopped into pellets, then dried and stored.
Extrude the hollow tube

Pellets melt in a second extruder and are forced through a ring-shaped die. A puller draws the soft tube along, and metal sizing plates keep its diameter even.
Cool over a water bath

The tube passes through water or over a chilled rod so the inside dimension is fixed before it hardens.
Chop to length

A knife assembly cuts the moving tube into straws.
Crimp the bendy part

Bendable straws get extra processing after cutting. Special equipment presses a ring of grooves into the tube so it can fold without collapsing.
Wrap and box

Many straws are sealed in paper sleeves and bundled into boxes.

Goes in
Paper

End of the linePlastic straw

Worth repeating

Straws were mostly paper until the 1960s, when polypropylene took over.
Rejected straws are ground up and remelted, because polypropylene can be melted again and again.
The oldest known straws are from the 3rd millennium BCE, made by Sumerians to drink beer.