Butadiene, heats polymerization

C4H6 1,3- butadiene heat generation, violent polymeriza- tion fire, toxic gas generation heat generation, violent polymeriza- tion fla mmable peroxidizes polymerizes decomposes ... 

AlEt2Cl/CoX2NR3/(MeOH)/Butadiene. All polymerizations were carried out in 250-ml. crown-capped pressure bottles with perbunan/aluminum foil seals. The bottles were dried before use by heating overnight at 120° C. and... 

An alternative method of initiation is through the use of the radical anion produced from the reaction of sodium (or lithium) with naphthalene. Such radical anions react with styrene by electron transfer to form styrene radical anions these dimerize to produce a dianion, which initiates polymerization as outlined in Scheme 14. One particular feature of this method is that polymerization proceeds outwards from the centre. Subsequent reaction of the living chains ends with another suitable monomer system produces a triblock copolymer. This is the principle by which styrene-butadiene-styrene triblock copolymers (formed when butadiene is polymerized in the same way. and styrene is added as second monomer) are produced commercially. This material behaves as a thermoplastic elastomer, since the rigid styrene blocks form cross-links at room temperature on heating these rigid styrene portions soften, allowins the material to be remoulded. ... 

Inhibited butadiene of polymerization purity is available in cybnders (3.8- 54 L), tank cars, tank trucks, and pipelines (96,97). The cylinders may be shipped by motor or rail freight (98). Containers are subject to regulations of the Department of Transportation and must be labeled Flammable Gas (96). Butadiene is usually stored in bulk imder refrigeration rather than pressure in order to suppress formation of the dimer 1-vinylcyclohexene (99). Smaller quantities in cylinders under pressure should be kept away from sources of ignition and heat. 

Interpenetrating Polymer Networks (IPN). Polymerization of vinyl and diene monomers over an already formed molecule held in a pol5uner particle represents a special case of copoljnnerization. The interpenetrating polymer networks (qv) thus formed overcome many of the miscibility and other problems associated with physical blends of individual copolymers and leads to new compositions that are useful for coatings, adhesives, and caulks (14). Polychloroprene IPNs have been made by co-curing copolymers of l-chloro-l,3-butadiene [627-22-5], The 1-chloro-l,3-butadiene comonomer polymerizes in a fashion to increase the allylic chloride concentration in the copolymer backbone. The butadiene copolymer with l-chloro-l,3-butadiene (29) and octyl acrylate copolymer (30) improved the low temperature brittleness, oil resistance, and heat resistance of polychloroprene. 

With the advent of World War I the situation in Germany, as far as the supply of natural rubber was concerned, became acute and renewed research efforts were made. Isoprene was expensive and, although quite a good rubber could be made from it by heat polymerization, yields were poor. Sodium-catalyzed polymerizations gave higher yields but inferior products. Since at that time butadiene was both very difiicult and expensive to prepare, dimethyl butadiene became the preferred monomer. In 1917 the Germans commenced the first substantial commercial production of a man-made rubber, from dimethyl butadiene. Two versions were made. Methyl Rubber W, by heat polymerization at about 70 C over a period of five months and... 

By the end of the 19th century isoprene had been converted to a rubber-like material by Tilden, Bouchardat and others. During the first decade of the 20th century other dienes such as butadiene and dimethyl butadiene had been polymerized. By 1909 F. Hofmann and his associates had filed patents on the heat polymerization of these monomers. 

SBR is a low-cost rubber with slightly better heat aging and wear resistance than NR for tires. SBR grades are largely established by the bound styrene/butadiene ratio, polymerization conditions such as reaction temperature, and auxiliary chemicals added during polymerization. 

The impact of cold GR-S was quite pronounced. The U.S. government edicted that all of the emulsion SBR plants switch to the cold process. This required addition of refrigeration capacity in these plants as well as other significant changes, such as insulation of reactors, improved vacuum to reduce oxygen that retards polymerization, and the heating of latex in blowdown tanks to aid in the disengagement of butadiene when transferred to the flash tanks. 

Polymerization processes are characterized by extremes. Industrial products are mixtures with molecular weights of lO" to 10. In a particular polymerization of styrene the viscosity increased by a fac tor of lO " as conversion went from 0 to 60 percent. The adiabatic reaction temperature for complete polymerization of ethylene is 1,800 K (3,240 R). Heat transfer coefficients in stirred tanks with high viscosities can be as low as 25 W/(m °C) (16.2 Btu/[h fH °F]). Reaction times for butadiene-styrene rubbers are 8 to 12 h polyethylene molecules continue to grow lor 30 min whereas ethyl acrylate in 20% emulsion reacts in less than 1 min, so monomer must be added gradually to keep the temperature within hmits. Initiators of the chain reactions have concentration of 10" g mol/L so they are highly sensitive to poisons and impurities. 

Acrylonitrile-butadiene rubber (also called nitrile or nitrile butadiene rubber) was commercially available in 1936 under the name Buna-N. It was obtained by emulsion polymerization of acrylonitrile and butadiene. During World War II, NBR was used to replace natural rubber. After World War II, NBR was still used due to its excellent properties, such as high oil and plasticizer resistance, excellent heat resistance, good adhesion to metallic substrates, and good compatibility with several compounding ingredients. 

NR, styrene-butadiene mbber (SBR), polybutadiene rubber, nitrile mbber, acrylic copolymer, ethylene-vinyl acetate (EVA) copolymer, and A-B-A type block copolymer with conjugated dienes have been used to prepare pressure-sensitive adhesives by EB radiation [116-126]. It is not necessary to heat up the sample to join the elastomeric joints. This has only been possible due to cross-linking procedure by EB irradiation [127]. Polyfunctional acrylates, tackifier resin, and other additives have also been used to improve adhesive properties. Sasaki et al. [128] have studied the EB radiation-curable pressure-sensitive adhesives from dimer acid-based polyester urethane diacrylate with various methacrylate monomers. Acrylamide has been polymerized in the intercalation space of montmorillonite using an EB. The polymerization condition has been studied using a statistical method. The product shows a good water adsorption and retention capacity [129]. 

Observations on the polymerization of readily polymerizable vinyl monomers such as styrene, vinyl chloride, and butadiene date back approximately to the first recorded isolation of the monomer in each case. Simon 2 reported in 1839 the conversion of styrene to a gelatinous mass, and Berthelot applied the term polymerization to the process in 1866. Bouchardat polymerized isoprene to a rubberlike substance. Depolymerization of a vinyl polymer to its monomer (and other products as well) by heating at elevated temperatures was frequently noted. Lemoine thought that these transformations of styrene could be likened to a reversible dissociation, a commonly held view. While the terms polymerization and depolymerization were quite generally applied in this sense, the constitution of the polymers was almost completely unknown. 

POLYMERIZING Has the tendency to self-react to form larger molecules, while possibly generating enough heat/gases to burst a container Acrylic acid, styrene, 1,3-butadiene... 

A sketch of the thermogram obtained for the thermal decomposition of Fe(CO)(l,3-C4H6)2 at 418 K is shown in figure 9.5 [163]. The endothermic part reflects the heating (from 298 K to 418 K) and the melting of the sample and probably also some thermal decomposition. The exothermic peak of the thermogram was attributed to the polymerization of butadiene. Because area B is larger than A, the overall process (equation 9.10) is exothermic. 

Besides butadiene, another important monomer for the synthetic elastomer industry is chloroprene, which is polymerized to the chemically resistant polychloroprene. It is made by chlorination of butadiene follow by dehydrochlorination. As with most conjugated dienes, addition occurs either 1,2 or 1,4 because the intermediate allyl carbocation is delocalized. The 1,4-isomer can be isomerized to the 1,2-isomer by heating with cuprous chloride. 

Most polystyrene products are not homopolystyrene since the latter is relatively brittle with low impact and solvent resistance (Secs. 3-14b, 6-la). Various combinations of copolymerization and blending are used to improve the properties of polystyrene [Moore, 1989]. Copolymerization of styrene with 1,3-butadiene imparts sufficient flexibility to yield elastomeric products [styrene-1,3-butadiene rubbers (SBR)]. Most SBR rubbers (trade names Buna, GR-S, Philprene) are about 25% styrene-75% 1,3-butadiene copolymer produced by emulsion polymerization some are produced by anionic polymerization. About 2 billion pounds per year are produced in the United States. SBR is similar to natural rubber in tensile strength, has somewhat better ozone resistance and weatherability but has poorer resilience and greater heat buildup. SBR can be blended with oil (referred to as oil-extended SBR) to lower raw material costs without excessive loss of physical properties. SBR is also blended with other polymers to combine properties. The major use for SBR is in tires. Other uses include belting, hose, molded and extruded goods, flooring, shoe soles, coated fabrics, and electrical insulation. 

Figures 1 and 2 show the dependence of polymer microstructure on the molecular weight of the polymer and therefore on the initial initiator concentration. The polymerization temperature also has an effect on the microstructure as can be seen in Figure 3 for polybutadiene. The overall heat activation energy leading to 1,2 addition is greater than that leading to 1,4 addition.2 IZ In summary, the stereochemistry of polymerization of butadiene and isoprene is sensitive to initiator level, polymerization temperature and solvent. The initiator structure (i.e., organic moiety of the initiator), the monomer concentration and conversion have essentially no effect on polymer microstructure.

This group covers polymeric peroxides of indeterminate structure rather than polyfunctional macromolecules of known structure. These usually arise from autoxidation of susceptible monomers and are of very limited stability or explosive. Polymeric peroxide species described as hazardous include those derived from butadiene (highly explosive) isoprene, dimethylbutadiene (both strongly explosive) 1,5-p-menthadiene, 1,3-cyclohexadiene (both explode at 110°C) methyl methacrylate, vinyl acetate, styrene (all explode above 40°C) diethyl ether (extremely explosive even below 100°C ) and 1,1-diphenylethylene, cyclo-pentadiene (both explode on heating). 

While vinyl acetate is normally polymerized in batch or continuous stirred tank reactors, continuous reactors offer the possibility of better heat transfer and more uniform quality. Tubular reactors have been used to produce polystyrene by a mass process (1, 2), and to produce emulsion polymers from styrene and styrene-butadiene (3 -6). The use of mixed emulsifiers to produce mono-disperse latexes has been applied to polyvinyl toluene (5). Dunn and Taylor have proposed that nucleation in seeded vinyl acetate emulsion is prevented by entrapment of oligomeric radicals by the seed particles (6j. Because of the solubility of vinyl acetate in water, Smith -Ewart kinetics (case 2) does not seem to apply, but the kinetic models developed by Ugelstad (7J and Friis (8 ) seem to be more appropriate. 

---