How synthetic rubber is made

The most common synthetic rubber is a copolymer of styrene and butadiene, made in giant vats of soapy water.

stations: 6
things upstream: 10
raw sources: 4
steps from the ground: 6

The short version

Synthetic rubber is made by linking petrochemical monomers into elastic chains. For styrene-butadiene rubber, butadiene and styrene are emulsified in soapy water and polymerized into a milky latex. Acid and salt coagulate the latex into crumbs, which are washed, dried and pressed into bales.

Collect butadiene from the cracker

A steam cracker running on naphtha produces butadiene alongside ethylene. It is separated by distillation and kept under pressure as a liquid.

Goes in
Naphtha
Make styrene

Styrene is built from benzene and ethylene at a nearby plant. It is the second half of the most common synthetic rubber.

Goes in
Benzene Ethylene Styrene
Emulsify and polymerize

The monomers are stirred into water with soap-like emulsifiers and an initiator in a train of reactors. Rubbery particles grow inside tiny droplets until the mixture is milky latex.

Goes in
Water
Strip the leftovers

Unreacted monomers are boiled out of the latex and recycled. Antioxidants are added so the rubber will last in storage.
Coagulate into crumb

Acid and salt break the latex, and rubber clumps float out as crumb. The crumb is washed free of soap and other residues.
Dry and press into bales

Crumb travels through a long dryer and is compressed into bales wrapped in plastic. Tire factories buy them by the truckload.

End of the lineSynthetic rubber Next it goes into toothbrush, syringe, vulcanized rubber and 8 more.

Worth repeating

Studies published in 1930 by Sergey Lebedev, Wallace Carothers and Hermann Staudinger helped lead to the synthetic rubber neoprene in 1931.
By mid-1942 the Axis powers controlled almost all the world's natural rubber supply, which pushed the United States to expand synthetic rubber production during World War II.