In fact, such is her attachment to it, I have to stop her from running into the street to save her new polychloroprene friend.
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Typical rubbers used conventionally include natural rubber, nitrile rubber, polychloroprene, polybutadiene, styrene-butadiene and fluorinated rubbers.
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Chloroprene is the common name for 2-chlorobuta-1,3-diene (IUPAC name) with the chemical formula CH2=CCl−CH=CH2. Chloroprene is a colorless volatile liquid, almost exclusively used as a monomer for the production of the polymer polychloroprene, a type of synthetic rubber. Polychloroprene is better known as Neoprene, the trade name given by DuPont.
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Some insulation is provided by the suit, and the rest by garments worn underneath. Chemical structure of the repeating unit of polychloroprene Neoprene (also polychloroprene) is a family of synthetic rubbers that are produced by polymerization of chloroprene.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.
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In some cases, thioureas can be prepared by thiation of ureas using phosphorus pentasulfide. Ethylene thiourea is an excellent accelerant of vulcanization of neoprene and polychloroprene rubbers.
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Arnold Miller Collins (1899-1982) a chemist at DuPont who, working under Elmer Bolton and Wallace Carothers, first isolated polychloroprene and 2-chloro-1, 3-butadiene in 1930.
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Ethylene thioureas are an excellent accelerant of vulcanization of neoprene and polychloroprene rubbers. In commercial use is the N,N'-diphenylethylenethiourea. Due to reproductive toxicity, carcinogenicity, and mutagenicity, alternatives are being sought to the ethylenethioureas. One candidate replacement is N-methyl-2-thiazolidinethione.
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Some people are allergic to neoprene while others can get dermatitis from thiourea residues left from its production. The most common accelerator in the vulcanization of polychloroprene is ethylene thiourea (ETU), which has been classified as reprotoxic. The European rubber industry project called SafeRubber focused on alternatives to the use of ETU.
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Most conventionally used accelerators are problematic when CR rubbers are cured and the most important accelerator has been found to be ethylene thiourea (ETU) which, although being an excellent and proven accelerator for polychloroprene, has been classified as reprotoxic. The European rubber industry has started a research project SafeRubber to develop a safer alternative to the use of ETU.
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Vulcanization is a step in the processing of several classes of rubbers, including polychloroprene (Neoprene), styrene-butadiene, and polyisoprene, which is chemically similar to natural rubber. Charles Goodyear's discovery of vulcanization, involving the heating of polyisoprene with sulfur, was revolutionary because it converted a sticky and almost useless material into an elastomer which could be fabricated into useful products.
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Red lead has been used as a pigment for primer paints for iron objects. Due to its toxicity, its use is being limited. It finds limited use in some amateur pyrotechnics as a delay charge and was used in the past in the manufacture of dragon's egg pyrotechnic stars. Red lead is used as a curing agent in some polychloroprene rubber compounds.
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Ozone cracking in Natural rubber tubing Ozone cracking is a form of stress corrosion cracking where active chemical species attack products of a susceptible material. Ozone cracking was once commonly seen in the sidewalls of tires but is now rare owing to the use of antiozonants. Other means of prevention include replacing susceptible rubbers with resistant elastomers such as polychloroprene, EPDM or Viton.
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The vulcanization of neoprene or polychloroprene rubber (CR rubber) is carried out using metal oxides (specifically MgO and ZnO, sometimes Pb3O4) rather than sulfur compounds which are presently used with many natural and synthetic rubbers. In addition, because of various processing factors (principally scorch, this being the premature cross-linking of rubbers due to the influence of heat), the choice of accelerator is governed by different rules to other diene rubbers. Most conventionally used accelerators are problematic when CR rubbers are cured and the most important accelerant has been found to be ethylene thiourea (ETU), which, although being an excellent and proven accelerator for polychloroprene, has been classified as reprotoxic. The European rubber industry has started a research project SafeRubberSafeRubber, an alternative accelerator to the development of rubber to develop a safer alternative to the use of ETU.
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Contact adhesives are used in strong bonds with high shear-resistance like laminates, such as bonding Formica to a wooden counter, and in footwear, as in attaching outsoles to uppers. Natural rubber and polychloroprene (Neoprene) are commonly used contact adhesives. Both of these elastomers undergo strain crystallization. Contact adhesives must be applied to both surfaces and allowed some time to dry before the two surfaces are pushed together.
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The higher the concentration, the greater the number of cracks formed. Ozone-resistant elastomers include EPDM, fluoroelastomers like Viton and polychloroprene rubbers like Neoprene. Attack is less likely because double bonds form a very small proportion of the chains, and with the latter, the chlorination reduces the electron density in the double bonds, therefore lowering their propensity to react with ozone. Silicone rubber, Hypalon and polyurethanes are also ozone-resistant.
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Often the best technique is ESEM using the X-ray elemental analysis facility on the microscope. Although the method only provides elemental analysis, it can provide clues as to the identity of the elastomer being examined. Thus the presence of substantial amounts of chlorine indicates polychloroprene while the presence of nitrogen indicates nitrile rubber. The method is also useful in confirming ozone cracking by the large amounts of oxygen present on cracked surfaces.
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Another important group of primary accelerators is formed by the thiazoles. The two main products are mercaptobenzothiazole (MBT) and mercaptobenzothiazole disulfide (MBTS), a product formed by oxidative coupling of two MBT molecules. The thiazoles are used for the vulcanization of thick articles, and as basic accelerator in EPDM compounds (ethylene- propylene-diene rubbers), in combination with mixtures of ultra-accelerators. In the vulcanization of neoprene or polychloroprene rubber (CR rubber) the choice of accelerator is governed by different rules to other diene rubbers.
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The wide variety of ester chemistries that are in production include sebacates, adipates, terephthalates, dibenzoates, gluterates, phthalates, azelates, and other specialty blends. This broad product line provides an array of performance benefits required for the many elastomer applications such as tubing and hose products, flooring, wall-coverings, seals and gaskets, belts, wire and cable, and print rolls. Low to high polarity esters provide utility in a wide range of elastomers including nitrile, polychloroprene, EPDM, chlorinated polyethylene, and epichlorohydrin. Plasticizer-elastomer interaction is governed by many factors such as solubility parameter, molecular weight, and chemical structure.
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Upon the clogging of equipment associated with occupational chloroprene use, employers should ensure that their employees are wearing the proper PPE and set up administrative controls so that skin exposure to and inhalation of chloroprene is avoided. Only one fatality as a result of chloroprene intoxication has been recorded which was a result of cleaning a container used for chloroprene.Hierarchy of Controls The primary occupational concern for chloroprene is limited to the facilities producing chloroprene and using chloroprene to produce the synthetic rubber, polychloroprene. NIOSH developed a list of actions to address specific workplace hazards.
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In the early 20th century the Leblanc process was effectively replaced by the Solvay process, which did not produce HCl. However, hydrogen chloride production continued as a step in hydrochloric acid production. Historical uses of hydrogen chloride in the 20th century include hydrochlorinations of alkynes in producing the chlorinated monomers chloroprene and vinyl chloride, which are subsequently polymerized to make polychloroprene (Neoprene) and polyvinyl chloride (PVC), respectively. In the production of vinyl chloride, acetylene (C2H2) is hydrochlorinated by adding the HCl across the triple bond of the C2H2 molecule, turning the triple into a double bond, yielding vinyl chloride.
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Rubbers with saturated polymer backbones, such as EPDM, have much better resistance to heat, light and ozone than unsaturated rubbers such as natural rubber, SBR or polychloroprene (Neoprene). As such, EPDM can be formulated to be resistant to temperatures as high as 150 °C, and, properly formulated, can be used outside for many years or decades without degradation. EPDM has good low temperature properties, with elastic properties to temperatures as low as -40 °C depending on the grade and the formulation. fleece on the back, used for waterproofing roofs As with most rubbers, EPDM is always used compounded with fillers such as carbon black and calcium carbonate, with plasticisers such as paraffinic oils, and has useful rubbery properties only when crosslinked.
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