Chloro rubber

In addition to polyvinyl chloride (PVC), the chlorine-containing polymers and different copolymers of vinyl chloride are polyvinylidene chloride, chloro-rubber, rubber hydrochloride, chlorinated polyolefins, polychloro-prene, and polytrifluorochloroethylene. In addition to detecting chlorine with the Beilstein test (see Chapter 4), these polymers can be identified by using the color reaction with pyridine (see Table 6.2). 

As the demand for rubber increased so did the chemical industry s efforts to prepare a synthetic sub stitute One of the first elastomers (a synthetic poly mer that possesses elasticity) to find a commercial niche was neoprene discovered by chemists at Du Pont in 1931 Neoprene is produced by free radical polymerization of 2 chloro 1 3 butadiene and has the greatest variety of applications of any elastomer Some uses include electrical insulation conveyer belts hoses and weather balloons... 

CIIR chloro-isobutene-isoprene rubber (chlorinated butyl rubber)... 

Polychloroprene rubber (CR) is the most popular and versatile of the elastomers used in adhesives. In the early 1920s, Dr. Nieuwland of the University of Notre Dame synthesized divinyl acetylene from acetylene using copper(l) chloride as catalyst. A few years later, Du Pont scientists joined Dr. Nieuwland s research and prepared monovinyl acetylene, from which, by controlled reaction with hydrochloric acid, the chloroprene monomer (2-chloro-l, 3-butadiene) was obtained. Upon polymerization of chloroprene a rubber-like polymer was obtained. In 1932 it was commercialized under the tradename DuPrene which was changed to Neoprene by DuPont de Nemours in 1936. 

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. 

Chloroprene (2-chloro 1,3-butadiene), a conjugated non-hydrocarbon diolefm, is a liquid that boils at 59.2°C and while only slightly soluble in water it is soluble in alcohol. The main use of chloroprene is to polymerize it to neoprene rubber. 

Polychloroprene is the oldest synthetic rubber. It is produced by the polymerization of 2-chloro-1,3-butadiene in a water emulsion with potassium sulfate as a catalyst ... 

A number of different synthetic rubbers are produced commercially by diene polymerization. Both cis- and frrms-polyisoprene can be made, and the synthetic rubber thus produced is similar to the natural material. Chloroprene (2-chloro-l,3-butadiene) is polymerized to yield neoprene, an excellent, although expensive, synthetic rubber with good weather resistance. Neoprene is used in the production of industrial hoses and gloves, among other things. 

Pandey et al. have used ultrasonic velocity measurement to study compatibility of EPDM and acrylonitrile-butadiene rubber (NBR) blends at various blend ratios and in the presence of compa-tibilizers, namely chloro-sulfonated polyethylene (CSM) and chlorinated polyethylene (CM) [22]. They used an ultrasonic interferometer to measure sound velocity in solutions of the mbbers and then-blends. A plot of ultrasonic velocity versus composition of the blends is given in Eigure 11.1. Whereas the solution of the neat blends exhibits a wavy curve (with rise and fall), the curves for blends with compatibihzers (CSM and CM) are hnear. They resemble the curves for free energy change versus composition, where sinusoidal curves in the middle represent immiscibility and upper and lower curves stand for miscibihty. Similar curves are obtained for solutions containing 2 and 5 wt% of the blends. These results were confirmed by measurements with atomic force microscopy (AEM) and dynamic mechanical analysis as shown in Eigures 11.2 and 11.3. Substantial earher work on binary and ternary blends, particularly using EPDM and nitrile mbber, has been reported. 

When two polymers interact or react with each other, they are likely to provide a compatible, even a miscible, blend. Epoxidized natural rubber (ENR) interacts with chloro-sulfonated polyethylene (Hypalon) and polyvinyl chloride (PVC) forming partially miscible and miscible blends, respectively, due to the reaction between chlorosulfonic acid group and chlorine with epoxy group of ENR. Chiu et al. have studied the blends of chlorinated polyethylene (CR) with ENR at blend ratios of 75 25, 50 50, and 25 75, as well as pure rubbers using sulfur (Sg), 2-mercapto-benzothiazole, and 2-benzothiazole disulfide as vulcanizing agents [32]. They have studied Mooney viscosity, scorch... 

Preparation of tricesium di-p-chloro-hexachloro-p-hydrido-dimolybdate-(3 ), Cs3[Mo2ClgH]. Molybdenum(II) acetate (10.0 g, 23.4 mmole) is placed in a three-necked, 500-mL flask containing a Teflon-coated stirrer bar. The flask is capped with three rubber septums, and a thermometer is inserted through one of the septums. After the flask and its contents have... 

Fluorocarbon Resins. This term includes polytetrafluoroethylene, polymers of chloro-trifluoroethylene (fluorothene), vinylidene fluoride (H2C CF2)j hexafluoropropylene (C3Ffl) and similar compds. These polymers are thermoplastic, inert to chemicals and oxidation. They have high heat stability, retain their useful props at both extremely low and high temps, have high electrical resistance to moisture. The materials are available as re sins, powders, and dispersions, and as films, sheets, tubes, rods and tapes. Some of them are rubber-like. Commercially available varieties are Kel-F , Teflon , Fluorel , Aclar and "Halon ... 

Natural rubber (Hevea brasiliensis) is as-poly-2-methyl-1,4-butadiene, and gutta-percha (Palaquium oblongi/olium) and balata (Minusops globosa) are polymers of isoprene (2-methyl-1,4-butadiene) with trans configurations. Neoprene is a polymer of 2-chloro-1,3-butadiene (chloroprene). 

The copolymer of isobutylene with a few percent isoprenc (butyl rubber) can be cured to produce an ozone-resistant elastomer with low permeability to oxygen and nitrogen. Butyl rubber has a Tt of — 70 C a refractive index of 1.5081, and a coefficient of linear expansion of 5.7 X 10 cm/cxn C. Chloro and bromo butyl rubber are more resistant to the permeation of oxygen and nitrogen than butyl rubber. 

Exposure to ori/70-toluidine was reported to occur in an Italian plant producing fuchsin (magenta) and safranine T-based dyes (Rubino et al., 1982), in a German plant producing 4-chloro-ori/70-toluidine (Stasik, 1988) and in a plant producing rubber chemicals in the United Kingdom (Sorahan et al, 2000), but no data on exposure levels were provided. 

A. Triethyl a-phtkalimidoethane-a,a, -tricarboxylate. Three hundred and twenty-seven grams (1.0 mole) of diethyl sodium phthalimidomalonate and 735 g. (6.0 moles) of ethyl chloro-acetate (b.p. 144-145°) are placed in a 2-1. Claisen flask fitted with a reflux condenser and rubber stoppers. The mixture is heated under reflux in an oil bath at 150-160° for 2.25 hours. The excess ethyl chloroacetate is removed by distillation at 30 mm. until the heating bath temperature reaches 150° and no more distillate is obtained (Note 1). The brown residual mass is... 

Fig. 46 Stress-strain curves for the pure chloroprene rubber (CR gum) and PTFE-based chloro-prene composites...

A 250-ml., three-necked, round-bottomed flask is equipped with a 50-ml. pressure-equalizing dropping funnel capped by a rubber septum, an efficient reflux condenser connected to a nitrogen inlet, and a magnetic stirrer (Note 1). The flask is charged with 7.02 g. (0.05 mole) of a-chloro-p-xylene (Note 2) and 45.6 g. (0.63 mole) of ethyl vinyl ether (Note 3). A solution of 7.06 g. (0.05 mole) of... 

Another chlorinated compound which, like vinyl chloride, is used only in its polymeric form, is chloroprene (2-chloro-l,3-butadiene), which is polymerized to make neoprene, first produced in 1940. As far as is known (17) y the monomer is made commercially only from acetylene via addition of hydrochloric acid to monovinylacetylene in the presence of cuprous chloride, but syntheses from butylenes or butadiene have been described. The production of chloroprene exceeded 100,000,000 pounds per year at the wartime peak and has been somewhat lower since then, but in view of the many valuable properties of the neoprene rubber it will continue to be important. 

Buist and Davies during a study of natural rubber and chloro-prene rubber stocks containing various carbon blacks point out that certain properties are closely related. For example, for natural rubber the following groups are highly correlated. 

When all the solid has been added, the solution is gently heated until the evolution of hydrogen chloride has ceased care must be taken not to overheat it otherwise some product may be lost through volatilization. The material is then distilled, using an air condenser, until the temperature of the vapor reaches 165°C the receiver consists of a 250-ml round flask protected from moisture. As the acid attacks cork and rubber readily an all-glass apparatus must be used. The crude product is redistilled from the receiver and the colorless liquid is collected at 149-154°C pure chloro-... 

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