Butadienes decomposition temperature

The thermal stability of poly(vinyl chloride) is improved greatly by the in situ polymerization of butadiene or by reaction with preformed cis-1,4-polybutadiene using a diethyl-aluminum chloride-cobalt compound catalyst system. The improved thermal stability at 3-10% add-on is manifested by greatly reduced discoloration when the modified poly-(vinyl chloride) is compression molded at 200°C in air in the absence of a stabilizer, hydrogen chloride evolution at 180°C is retarded, and the temperature for the onset of HCl evolution and the peak decomposition temperature (DTA) increase, i.e. 260°-280°C and 290°-325° C, respectively, compared with 240°-260°C and 260°-280°C for the unmodified homopolymer, in the absence of stabilizer. The grafting reaction may be carried out on suspension, emulsion, or bulk polymerized poly(vinyl chloride) with little or no change in the glass transition temperature. 

The conductivity of the oxides of zinc, iron, and nickel is known to be highly sensitive to small amounts (< 1 mole %) of oxides of similar cation radius, but different valency (e.g., Li+, Al, Ga +, Cr ", and Ti +). The activity and selectivity of such promoted catalyst pellets have been measured for the dehydrogenation of butene-1 to butadiene at temperatures between 600 and 660° in the presence of 10-20 vol. of steam as a diluent gas. The decomposition of butadiene has been studied as a separate reaction. 

On decomposition, the polybutylene terephthalate (PBT) polymers give off mainly water, carbon dioxide, butadiene, tetrahydrofuran (THF) and PBT oligomers. The flame retardants marginally increased the polymer decomposition temperature (274). 

The molecular mass of the wax-like compounds, which are volatile at the decomposition temperatures and comprise the basic mass (82-97%) of the products of the thermal degradation of polybutadiene is 739. The average yield of monomer on degradation of poly butadiene does not exceed 1.5% mass of the total quantity of volatile compounds, a result which may be associated with both the partial polymerisation of the monomer produced, which is kept at room temperature, and the formation of vinylcyclohexane ... 

Thermoplastics such as polypropylene, polycarbonate, nylon, and thermo set such as epoxy, as well as thermoplastic elastomers such as butadiene-styrene di block copolymer, have been reinforced with carbon nanofibers for example. Carbon nanofibers with 0.5 wt% loading were dry-mixed with polypropylene powder by mechanical means, and extruded into filaments by using a single screw extruder. Decomposition temperature and tensile modulus and tensile strength have increased because of dispersion of CNF [121] (Fig. 8.19). 

This is an exothermic, reversible, homogeneous reaction taking place in a single liquid phase. The liquid butadiene feed contains 0.5 percent normal butane as an impurity. The sulfur dioxide is essentially pure. The mole ratio of sulfur dioxide to butadiene must be kept above 1 to prevent unwanted polymerization reactions. A value of 1.2 is assumed. The temperature in the process must be kept above 65°C to prevent crystallization of the butadiene sulfone but below lOO C to prevent its decomposition. The product must contain less than 0.5 wt% butadiene and less thM 0.3 wt% sulfur dioxide. 

AlkyUithium compounds are primarily used as initiators for polymerizations of styrenes and dienes (52). These initiators are too reactive for alkyl methacrylates and vinylpyridines. / -ButyUithium [109-72-8] is used commercially to initiate anionic homopolymerization and copolymerization of butadiene, isoprene, and styrene with linear and branched stmctures. Because of the high degree of association (hexameric), -butyIUthium-initiated polymerizations are often effected at elevated temperatures (>50° C) to increase the rate of initiation relative to propagation and thus to obtain polymers with narrower molecular weight distributions (53). Hydrocarbon solutions of this initiator are quite stable at room temperature for extended periods of time the rate of decomposition per month is 0.06% at 20°C (39). 

The polyperoxidation of 1,3-dienes is even more dangerous because they are more reactive and some of their polyperoxides are insoluble. With butadiene, the polyperoxidation takes place at temperatures lower than -113 C the oxygen is absorbed very quickly and forms insoluble polyperoxides that precipitate. It was estimated that at a temperature of 25°C the critical mass of such a compound consists of a sphere of diameter 9 cm. This diameter decreases quickly with the temperature. Isoprene behaves in the same way, but its polyperoxide is soluble, in these conditions, the monomer can absorb any temperature rise which would be caused by the beginning of a decomposition, thus reducing risks. If the monomer evaporates, a gum that detonates at 20°C is formed if the medium is stirred. With cyclopentadiene, polyperoxide is more stable and only detonates at a high temperature. 

Conlin148 also studied the pyrolysis of 1-methyl-1-silacyclobutane in the presence of excess butadiene at various temperatures where the decomposition followed first-order kinetics and where the silene isomerized to the isomeric silylene prior to reacting with the butadiene. The value for the preexponential factor A for the silene-to-silylene isomerization was found to be 9.6 0.2 s-1 and the Ewl for the isomerization was 30.4 kcal mol-1 with A// = 28.9 0.7 kcal mol-1 and AS = -18.5 0.9 cal mol-1 deg. More recently, the photochemical ring opening of l,l-dimethyl-2-phenylcyclobut-3-ene and its recyclization was studied. The Eact for cycli-zation was 9.4 kcal mol-1.113... 

Copper bromide has been used by Srebnik and co-workers to homocouple vinyl zirco-nocenes 75, thereby providing access to 2,3-dibora-1,3-butadienes (e. g., 76 Scheme 4.45), which retain their original geometrical relationships [76], These dimerizations readily take place at room temperature the products are stable to both air and moisture and can be purified by column chromatography on silica gel. Prolonged heating of the product at 150 °C was found not to lead to decomposition or even isomerization. Similarly, precur-... 

The stability of polystyryl carbanions is greatly decreased in polar solvents such as ethers. In addition to hydride elimination, termination in ether solvents proceeds by nucleophilic displacement at the C—O bond of the ether. The decomposition rate of polystyryllithium in THF at 20°C is a few percent per minute, but stability is significantly enhanced by using temperatures below 0°C [Quirk, 2002], Keep in mind that the stability of polymeric carbanions in the presence of monomers is usually sufficient to synthesize block copolymers because propagation rates are high. The living polymers of 1,3-butadiene and isoprene decay faster than do polystyryl carbanions. 

To control compatibility and other properties of butadiene/acrylonitrile copolymers with PVC, there is an optimum acrylonitrile content of 37%. For practical handling, the nitrile rubber is treated on rolls at normal temperatures, and afterwards the mixture is rolled with PVC at elevated temperatures. The reverse process—plasticizing PVC first and mixing with nitrile rubber afterwards—is not so favorable because discoloring and decomposition may occur. This can be avoided by simultaneously applying the liquid plasticizers. Nitrile content in-... 

Two recrystallizations from ligroin raise the melting point of the l-(/>-nitrophenyl)-l,3-butadiene to a constant value of 78.6-79.4°. The product can be kept for several weeks in a dark bottle at room temperature without evidence of decomposition. 

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