Neoprene (also polychloroprene) is a family of synthetic rubbers that are produced by polymerization of chloroprene.[1] Neoprene exhibits good chemical stability and maintains flexibility over a wide temperature range. Neoprene is sold either as solid rubber or in latex form and is used in a wide variety of commercial applications, such as laptop sleeves, orthopaedic braces (wrist, knee, etc.), electrical insulation, medical gloves, liquid and sheet-applied elastomeric membranes or flashings, and automotive fan belts.[2]
Production
Neoprene is produced by free-radical polymerization of chloroprene. In commercial production, this polymer is prepared by free radical emulsion polymerization. Polymerization is initiated using potassium persulfate. Bifunctional nucleophiles, metal oxides (e.g. zinc oxide), and thioureas are used to crosslink individual polymer strands.[3]
History
Neoprene was invented by DuPont scientists on April 17, 1930, after Elmer K. Bolton of DuPont attended a lecture by Fr Julius Arthur Nieuwland, a professor of chemistry at the University of Notre Dame. During his work on acetylene, Nieuwland produced divinyl acetylene, a jelly that firms into an elastic compound similar to rubber when passed over sulfur dichloride. After DuPont purchased the patent rights from the university, Wallace Carothers of DuPont took over commercial development of Nieuwland's discovery in collaboration with Nieuwland himself and DuPont chemists Arnold Collins, Ira Williams, and James Kirby.[4] Collins focused on monovinyl acetylene and allowed it to react with hydrogen chloride gas, manufacturing chloroprene.[5]
DuPont first marketed the compound in 1931 under the trade name DuPrene,[6] but its commercial possibilities were limited by the original manufacturing process, which left the product with a foul odor.
Mechanical properties
The high tensile performance of neoprene is a result of its highly regular backbone structure, which causes neoprene to undergo strain crystallization under tensile loading.[10] A two parameter (strain rate and temperature) hyperelastic model can accurately capture much of the mechanical response of neoprene.[11]
Exposure to acetone and heat have been shown to degrade the tensile strength and ultimate elongation of neoprene, likely due to a loss of plasticizers as well as an increase in crosslinking during heat exposure.[12] The response of neoprene to thermal aging depends not just on the highest temperature it is exposed to, but also on the exact temperature-time profile; this is a result of the competing factors of scission of the main polymer chain and oxidative cross-linking.[13] Chain scission leads to degradation, embrittlement, and a loss of toughness.[14]
Applications
General
Neoprene resists degradation more than natural or synthetic rubber. This relative inertness makes neoprene well suited for demanding applications such as gaskets, hoses, and corrosion-resistant coatings.[1] It can be used as a base for adhesives, noise isolation in power transformer installations, and as padding in external metal cases to protect the contents while allowing a snug fit. It resists burning better than exclusively hydrocarbon based rubbers,[20] resulting in its appearance in weather stripping for fire doors and in combat related attire such as gloves and face masks. Because of its tolerance of extreme conditions, neoprene is used to line landfills. Neoprene's burn point is around 260 °C (500 °F).[21]
In its native state, neoprene is a very pliable rubber-like material with insulating properties similar to rubber or other solid plastics.
Precautions
Some people are allergic to neoprene while others can get dermatitis from thiourea residues left from its production.[35]
The most common accelerator in the vulcanization of polychloroprene is ethylene thiourea (ETU), which has been classified as a reproductive toxin. From 2010 to 2013, the European rubber industry had a research project titled SafeRubber to develop a safer alternative to the use of ETU.[36]
See also
- Isoprene
External links
References
- Werner Obrecht, Jean-Pierre Lambert, Michael Happ, Christiane Oppenheimer-Stix, John Dunn and Ralf Krüger "Rubber, 4. Emulsion Rubbers" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH, Weinheim.^
- Technical information — Neoprene Du Pont Performance Elastomers, October 2003, retrieved 2008-02-06^
- Glenn E. Furman. Chloroprene Polymers Encyclopedia of Polymer Science and Technology, Wiley Online Library, 14 October 2005^