Polychloroprenes development

Polychloroprene, developed and sold under the trade name Neoprene by DuPont, was the first commercially successful synthetic elastomer. It is produced by free-radical emulsion polymerization of chloroprene (2-chloro-l,3-butadiene). The commercial material is mainly /raw5-l,4-polychloroprene, which is crystallizable. 

Chemistry of polychloroprene rubber. Polychloroprene elastomers are produced by free-radical emulsion polymerization of the 2-chloro-1,3-butadiene monomer. The monomer is prepared by either addition of hydrogen chloride to monovinyl acetylene or by the vapour phase chlorination of butadiene at 290-300°C. This latter process was developed in 1960 and produces a mixture of 3,4-dichlorobut-l-ene and 1,4-dichlorobut-2-ene, which has to be dehydrochlorinated with alkali to produce chloroprene. 

Neoprene AC (1947). This polychloroprene was developed to provide better viscosity stability and resistance to discolouration, but it cures much more slowly at room temperature. It is a fast crystallizing grade and contains about 90% trans-, 4 structure. 

Neoprene AF ( 963). It is a polychloroprene modified with methacrylic acid. Although it is a slow-crystallizing elastomer, the cohesive strength develops very rapidly and it has improved creep resistance at high temperature compared with Neoprene AC or AD. The improved properties of Neoprene AF are derived from the interaction between the carboxyl functionality with the metal oxides added in the solvent-borne polychloroprene adhesives. 

Neoprene XD. Developed in the 1980s, this polychloroprene family was prepared using special xanthogendisulphides as chain modifiers, offering improved processability and vulcanizate properties. In solution, these polychloroprenes show slow crystallization and high temperature resistance. 

New Neoprene M- and XD grades. These polychloroprenes were developed in the 1990s and combine low temperature flexibility, improved heat resistance and dynamic properties. 

About one dozen polychloroprene latices have been developed for adhesive... 

The properties of the solvent-bome CR adhesives depend on the molecular weight, degree of branching and rate of crystallization of the polymer. The ability of polychloroprene adhesives to crystallize is unique as compared to other elastomers. The higher the crystallization rate, the faster the adhesive strength development. 

The crystallization is responsible for the quick grab of polychloroprene adhesives. This rapid bond strength development allows the formation of immediate dry bonds without the need of clamping or pressing. 

In more recent years, lining compounds have been developed that vulcanise at ambient temperatures. Most polymers can be used for such compounds, although most materials are based on natural rubber, acrylonitrile-butadiene rubber and polychloroprene. These compounds contain accelerators which usually give rise to a material which has a delay in the onset of vulcanisation with a subsequent rapid rise in cross-link formation to give full vulcanisation in 6 to 8 weeks. Such materials, unless to be used within a few days of manufacture, are refrigerated to arrest the sel f-vulcanisation. 

Antifoam ingredients, in polychloroprene latex compounding, 19 857 Antifoggants, in color developer solutions, 19 248... 

Adhesives on the basis of a rubber are applied as watery dispersions, as solvents, or as solvent-free fluids. Sometimes the rubber is vulcanised after the gluing process, sometimes it remains uncured. Polymers often used are butyl rubber, polyisobutylene, and polychloroprene. A more recent development is the use of... 

Development of polybutadiene, polychloroprene and especially copolymers of butadiene andstyrene, as best replacements for natural rubber for tire-applications. Sodium used as catalyst Ring-opening polycondensation of caprolactam discovered by Schlack Formulation of the well-known Mark-Houwink equation for the viscometric determination of the molecular weight (mass)... 

The latexes upon which this industry developed were natural rubber and polychloroprene for solvent resistance. However, technology is advancing to permit penetration of carboxylated nitrile latex for optimized solvent resistance and tougher abrasion resistance. Among the competition to latexes in this field are poly(vinyl chloride) plastisols. As technology develops in producing small particle size latexes from polymers whose synthesis is loo water-sensitive for emulsion polymerization, the dipped goods industry will quickly convert to their utilization from the solvent-based cements of these polymers now employed Prime candidates include butyl rubber, EPDM, hypalon, and vlton. 

Neoprene, or polychloroprene, is a synthetic rubber discovered by the Du Pont Company in 1931. It is an organic polymer composed of carbon, hydrogen, and chlorine in the ratio of 55 5 40. Its relatively high chlorine content was responsible for the early recognized resistance of the polymer to burning. Practical use of this property was not developed until procedures for making foam structures from neoprene latex were developed in the 1940 s. The U.S. Navy adapted the material to make neoprene foam mattresses that reduced the fire hazards in the crews quarters of naval vessels. For many years neoprene has been the only material to meet Navy specifications for this application. 

Carothers, Wallace H. (1896-1937). Born in Iowa, Carothers obtained his doctorate in chemistry at the University of Illinois. He joined the research staff of Du Pont in 1928, where he undertook the development of polychloroprene (later called neoprene) that had been initiated by Nieuland s research on acetylene polymers. Carothers s crowning achievement was the synthesis of nylon, the reaction product of hexamethylenetetramine and adipic acid. Carothers s work in the polymerization mechanisms of fiber like synthetics of cyclic organic structures was brilliant and productive, and he is regarded as... 

Nieuland, Father J. A. (1878-1936). A Jesuit whose research on polymers of acetylene formed the basis for the development of polychloroprene (neoprene) in 1931. 

The first truly synthetic resin was developed by Baekeland in 1911 (phenol-formaldehyde). This was soon followed by a petroleum-derived product called coumarone-indene, which did indeed have the properties of a resin. The first synthetic elastomer was polychloroprene (1931) originated by Nieuwland and later called neoprene. Since then many new types of synthetic polymers have been synthesized, perhaps the most sophisticated of which are nylon and its congeners (polyamides, by Carothers), and the inorganic silicone group (Kipping). Other important types are alkyds, acrylics, aminoplasts, polyvinyl halides, polyester, epoxies, and polyolefins. 

Significant developments in synthetic rubber began at this time. Outstanding were the introduction of polychloroprene (neoprene) by Carothers, and of the oil-resistant polysulfide rubber Thiokol by Patrick. These were soon followed by styrene-butadiene copolymers, nitrile rubber, butyl rubber, and various other types, some of which were rushed into production for the war effort in the early 1940s. The stereospecific catalysts researched by Ziegler and Natta aided this development, including synthesis of true rubber hydrocarbon (polyisoprene). Since 1935 synthetic rubbers have been referred to as elastomers. 

The 1950s were known for the explosive development and growth in elastomers. DuPont Company developed a whole range of synthetic elastomers such as neoprene (polychloroprene), Hypalon (chloro-... 

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