Chloroprene peroxide

Chloroprene-dichlorobutadiene copolymers, 79 843 Chloroprene elastomers, 27 767 Chloroprene peroxides, 79 829 Chloroprene (Ml) reactivity ratios, 79 832t Chloroprene rubber, 9 561-562 79 828 Chloroprene-sulfur copolymerization, 79 833-834... 

Initiated Oxidation. The initial rates of oxidation of chloroprene, initiated with 2,2 -azobisisobutyronitrile, were measured in the range 20° to 40°C. at a total pressure of 700 mm. of Hg. The difficulty with these measurements was that chloroprene autoxidizes so readily that even when the initiator is used at the fairly massive concentration of 0.462M, the rate of oxidation is constant for only a few minutes before acceleration, resulting from a contribution to initiation from chloroprene peroxide. 

Chloroprene Peroxide. The efficiency of conversion of oxygen to total peroxides and hydroperoxide at various extents of oxidation was determined by iodometric methods. At up to 12% oxidation the proportion of hydroperoxide was constant at 20% of the whole. Ferrous thiocyanate likewise estimated a constant proportion (40%) of the total peroxide. Direct analysis of oxidates was somewhat difficult since the chloroprene tended to continue oxidizing during manipulation. Total peroxide estimates on chloroprene-free solutions of peroxide in toluene showed that at 20% oxidation 84% of the oxygen absorbed was present as peroxide groups. This is a minimum value since a small amount of the peroxide may have decomposed while chloroprene was being removed at —20°C. 

Table V. Calculated Values for for Decomposition of Chloroprene Peroxide and Kinetic Chain Lengths at 5 Mole % Oxidation...

Polymerization-grade chloroprene is typically at least 99.5% pure, excluding inert solvents that may be present. It must be substantially free of peroxides, polymer [9010-98-4], and inhibitors. A low, controlled concentration of inhibitor is sometimes specified. It must also be free of impurities that are acidic or that will generate additional acidity during emulsion polymerization. Typical impurities are 1-chlorobutadiene [627-22-5] and traces of chlorobutenes (from dehydrochlorination of dichlorobutanes produced from butenes in butadiene [106-99-0]), 3,4-dichlorobutene [760-23-6], and dimers of both chloroprene and butadiene. Gas chromatography is used for analysis of volatile impurities. Dissolved polymer can be detected by turbidity after precipitation with alcohol or determined gravimetrically. Inhibitors and dimers can interfere with quantitative determination of polymer either by precipitation or evaporation if significant amounts are present. 

The rate of absorption of oxygen by liquid butenyne increased with time, and eventually a yellow liquid phase separated. After evaporation of excess hydrocarbon, the yellow peroxidic liquid was explosive. Presence of 5% of chloroprene... 

Chloroprene monomer will autoxidise very rapidly with air, and even at 0°C it produces an unstable peroxide (a mixed 1,2- and 1,4-addition copolymer with oxygen), which effectively will catalyse exothermic polymerisation of the monomer. The kinetics of autoxidation have been studied [1], It forms popcorn polymer at a greater rate than does butadiene [2],... 

Hazardous when exposed to oxygen due to peroxide formation and subsequent peroxide initiation of polymerization Styrene Butadiene Tetrafluoroethylene Chlorotrifluoroethylene Vinyl acetylene Vinyl acetate Vinyl chloride Vinyl pyridine Chloroprene... 

An estimation of ZnCFO efficiency as vulcanization active component was carried out in modelling unfilled elastomeric compositions on the basis of isoprene, butadiene-nitrile, chloroprene and butyl rubbers of sulphur, thiuram, peroxide, metaloxide and resin vulcanization systems. 

ZnCFO is the effective vulcanization active component of the sulfur, thiuram, peroxide and metaloxide vulcanization systems for isoprene, nitrile-butadiene and chloroprene rubbers at the same time it is not effective in resin vulcanization system for butyl rubber. On a degree of positive influence on the properties of elastomeric compositions vulcanization systems with ZnCFO are arranged in a line ... 

Chloroprene was fractionally distilled under a reduced pressure of nitrogen. It was stored at — 80°C. in vacuo, and when required small amounts were distilled in vacuo into a subsidiary reservoir and from thence directly into the oxidation reactor. In this way chloroprene could be obtained completely free of peroxide, dimers, and higher polymers. 

Solutions of peroxide were prepared by oxidizing to the required extent, quenching the oxidation by cooling, and adding an excess of an inert diluent such as toluene. More than half the toluene was then pumped off while the oxidate was kept at — 20°C. After this procedure had been repeated twice, solutions of peroxide in toluene could be prepared in which the residual chloroprene concentration was about 0.5% (w./w.) of the peroxide. Complete removal of solvent gave faintly yellow viscous peroxidic material which was mildly explosive at room temperature. 

It was confirmed that no volatile peroxides were formed (10). Chloroprene was oxidized to 10% at 45°C. and then flash-distilled in... 

When the NMR spectrum of a 30% (w./v.) solution of peroxide in toluene was recorded at 34°C., absorption was observed between 8 2.74 and 5.46. There were seven main resonances, all multiplets, which were interpreted in terms of aliphatic hydrogen shifted by oxygen. Resonance from ethylenic hydrogen amounted to only a fraction of a proton. However, the sample darkened while in the instrument and probably decomposed extensively. When the spectrum of a solution of peroxide prepared by oxidation to 10.4 mole % was recorded using a cold probe at —35°C. a different picture was obtained. There was complex absorption from both ethylenic and saturated hydrogen which was interpreted as arising from a mixture of 1,2 and 1,4 oxygen copolymers in an approximate jatio of 1 to 2. In this sample the residual chloroprene amounted to 0.15% of the monomer units in the peroxide and dimers of chloroprene to 0.6% of the peroxide. 

In the early stages of the autoxidation of chloroprene the amount of oxygen absorbed increased as the square of the time. This dependence on time is frequently observed in autoxidations and is an approximation to that expected for an oxidation of long chain length, initiated by the first-order decomposition of the peroxidic product and terminated by a bimolecular reaction of the propagating peroxy radicals. 

The rate of absorption of oxygen by liquid butenyne increased with time, and eventually a yellow liquid phase separated. After evaporation of excess hydrocarbon, the yellow peroxidic liquid was explosive. Presence of 5% of chloroprene increased the rate of absorption 5—6-fold, and of 2% of water decreased the rate by 50%, but residues were explosive in each case [1], Explosive combustion in admixture with oxygen has been studied [2], and the effects of presence of nitrogen upon explosion parameters were determined [3]. 

Hazard of rapid polymerization initiated by internally formed peroxides List A. Normal liquids Discard or test for peroxides after 6 months1 Chloroprene (2-chloro-l,3-butadiene) Vinyl acetate... 

Although there are numerous references to the emulsion polymerization of vinyl ferrocene, they all appear to emanate from a single source (j4). These workers polymerized vinyl ferrocene alone, and with styrene, methyl methacrylate, and chloroprene. No characterization was reported other than elemental analysis. The molding temperatures reported (150 - 200 C) correspond to the Tg range indicated by Pittman ( ) for similar copolymers. The initiation system was preferably azobisisobutyronltrile, although potassium persulfate was also used. Organic peroxides were contraindicated, due to oxidation problems with the ferrocene moiety. 

The elastomeric sealing components of the metering valve are particularly critical. In those valves used with CFC propellants, the elastomeric seals have typically been formed from an acrylonitrile/butadiene rubber, which has been cured with sulfur. These rubber seals may not be fully compatible with HFA propellants hence, alternative elastomeric materials have been used. These materials include peroxide-cured acrylonitrile/ butadiene, ethylene-propylene diene monomer (EPDM), and chloroprene and thermoplastic elastomers (TPE). The elastomeric materials used to form the dynamic seals around the stem and the static gasket seal between the can and valve may differ based on the required properties of the rubber for the specific function of the seal. The most important characteristics of the elastomeric seals... 

Nonsulfur vulcanization has the same purpose as sulfur vulcanization and can be done using peroxides, quinones, azo compounds, or compounds that react similarly to sulfur such as selenium. However, nonsulfur vulcanization has lower practical importance. Commonly, chloroprene is vulcanized with nonsuifur compounds such as metal oxides (ZnO or MgO). 

Radical-Initiated Homopolymerization. When this homopolymerization is carried out with benzoyl peroxides or other radical formers in a manner analogous to emulsion polymerization of chloroprene, highly crosslinked polymers are formed. They are insoluble in organic solvents such as toluene, benzene, or chloroform. Radical polymerization in toluene, benzene, or hexane leads only to insoluble products. 

CHLOROPRENE (126-99-8) Forms explosive mixture with air (flash point -4°F/ —20°C). Unless inhibited, this material can form unstable peroxides that cause polymerization at room temperature. With inhibitor, it will polymerize in elevated temperatures above 100°F/38°C. Flow or agitation of substance may generate electrostatic charges due to low conductivity. Violent reaction with gaseous or liquid fluorine, alkali metals, metal powders, oxidizers. Attacks PVC natural, butyl, neoprene, and nitrile rubbers and coatings. Contact with divalent light metals can form highly reactive compounds. 

A considerable amount of work has also been done on the oxidation of the monomer and polymers of chloroprene. Chloroprene autoxidises rapidly, even at temperatures as low as 0°C, yielding a polymeric peroxide as the principle product [170,171]. The reaction has been found to be autocatalytic and, up to about 5 mole % oxidation, the mole % oxidation increased as the square of the time [170,172] above this extent of oxidation, the rate increased even more, apparently due to the subsequent reaction of the peroxide produced. The oxidations were so rapid that conventional initiators and inhibitors had less effect than could have been expected for less labile substrates. 

Bailey also found that more hydroperoxides were produced from the octene than form polychloroprene and suggested that chloroprene oxidation proceeded via peroxide formation involving carbon atoms located on non-adjacent double bonds... 

Hazard of Rapid Polymerization Initiated by Internally Formed Peroxides a. Normal Liquids Discard or test for peroxides cfier 6 months Chloroprene (2-chloro-l,3-buta-dieney Styrene... 

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