Neoprene

Summary

Neoprene is polychloroprene, a synthetic rubber made by free-radical emulsion polymerization of chloroprene. It tolerates harsh service and carries heavy loads in bearing pads, but UV exposure reduces its mechanical properties.

Cols

Image

Polychloroprene (CR): chemical name
DuPrene: original 1931 trade name
ETU: ethylene thiourea, a vulcanization accelerator and reproductive toxin

History and demand

Invention

1930: invented by DuPont (17 April); marketed as DuPrene in 1931; renamed neoprene in 1937
1932: about 8,000 lb produced; 1933: about 52,000 lb; output then doubled annually for five years

Sourcing

Named chloroprene rubber producers include Denka (Japan), ARLANXEO, and Tosoh; Shanxi Synthetic Rubber Group in China has 30,000 tons of polychloroprene capacity (market research)

Composition and production

Raw materials

Chloroprene polymerized with potassium persulfate; cross-linked with zinc oxide, bifunctional nucleophiles, or thioureas

Properties

Physical

Density: 1.23 g/cm3 (77 lb/ft3) solid; 0.1 to 0.3 g/cm3 foam
Glass transition: -43°C (-45°F)
Hardness: Shore 30 to 95

Mechanical

Tensile strength: 27.6 MPa (4,000 psi)
Elongation: 600 percent

Fire behavior

Burn point about 260°C (500°F)

Durability

Resists degradation better than natural or synthetic rubber; UV exposure reduces mechanical properties

Uses in buildings

Building elements

Sealants and Flashing: weatherstripping, including for fire doors, and flashings
Elastomeric bridge bearings carry heavy loads while allowing small horizontal movement
Liquid- and sheet-applied elastomeric membranes, including roofing

Pros and cons

Pros

Tolerates harsh conditions
Bridge bearings carry heavy load with small movement

Cons

UV reduces mechanical properties
Some people are allergic; thiourea residues cause dermatitis

Sustainability

Health

ETU is classed as a reproductive toxin; the SafeRubber project (2010 to 2013) sought a safer alternative

Manufacturing and cost

Main manufacturers and suppliers

DuPont

Sources

Wikipedia: Neoprene, https://en.wikipedia.org/wiki/Neoprene
Wikimedia Commons: Neoprene.jpg, photo by ProtoSpace (CC BY 2.0), https://commons.wikimedia.org/wiki/File:Neoprene.jpg
MarketResearch.com: chloroprene rubber (CR) industry research report, https://marketresearch.com/APO-Research-Inc-v4273/Chloroprene-Rubber-CR-Research-37883287