Benzoyl peroxide, ethylene

Benzophenone, structure of, 697 Benzoquinone, electrostatic potential map of, 631 Benzoyl group, 697 Benzoyl peroxide, ethylene... 

Benzoyl peroxide, ethylene, fluorine, metals, oxygen,... 

A copolymer of vinylidene fluoride (VDF) and ethylene was produced in a reactor at 80°C and at 60.5-70 MPa pressure. A stainless steel vessel was charged with 25 parts of water, 20 parts of VDF and 0.1 part of benzoyl peroxide. Ethylene was admitted into the reactor to 45 MPa at room temperature. Agitation and heating were started until a temperature of 80°C was reached and maintained at a pressure of 60.5-70 MPa by the admission of additional ethylene to the... 

Polymerization of styrene is carried out under free radical conditions often with benzoyl peroxide as the initiator Figure 1111 illustrates a step m the growth of a poly styrene chain by a mechanism analogous to that of the polymerization of ethylene (Sec tion 6 21)... 

Historically, ethylene potymerization was carried out at high pressure (1000-3000 atm) and high temperature (100-250 °C) in the presence of a catalyst such as benzoyl peroxide, although other catalysts and reaction conditions are now more often used. The key step is the addition of a radical to the ethylene double bond, a reaction similar in many respects to what takes place in the addition of an electrophile. In writing the mechanism, recall that a curved half-arrow, or "fishhook" A, is used to show the movement of a single electron, as opposed to the full curved arrow used to show the movement of an electron pair in a polar reaction. 

I Initiation The polymerization reaction is initiated when a few radicals are generated on heating a small amount of benzoyl peroxide catalyst to break the weak 0-0 bond. A benzoyloxy radical then adds to the C=C bond of ethylene to generate a carbon radical. One electron from the C=C bond pairs up with the odd electron on the benzoyloxy radical to form a C-O bond, and the other election remains on carbon. 

Interaction of ethylene and carbon tetrachloride at elevated temperatures and pressures, initiated with benzoyl peroxide as radical source, caused violent explosions on several occasions. Recommended precautions include use of minimum pressure and quantity of initiator, maximum agitation, and presence of water as an inert moderator of high specific heat. 

Radical Polymerization. Radical chain polymerization involves initiation, propagation, and termination. Consider the polymerization of ethylene. Initiation typically involves thermal homolysis of an initiator such as benzoyl peroxide... 

In 1988, Terry and coworkers attempted to homopolymerize ethylene, 1-octene, and 1-decene in supercritical C02 [87], The purpose of their work was to increase the viscosity of supercritical C02 for enhanced oil recovery applications. They utilized the free radical initiators benzoyl peroxide and fert-butyl-peroctoate and conducted polymerization for 24-48 h at 100-130 bar and 71 °C. In these experiments, the resulting polymers were not well studied, but solubility studies on the products confirmed that they were relatively insoluble in the continuous phase and thus were not effective as viscosity enhancing agents. In addition, a-olefins are known not to yield high polymer using free radical methods due to extensive chain transfer to monomer. 

It is manufactured by high pressure process by polymerising ethylene at high pressure of 1000-3000 atmosphere and temperature of 80-300°C. The common initiators used for polymerising ethylene are traces of oxygen, azobisisobutyronitrile, and benzoyl peroxide. 

One starts free-radical polymerizahon by adding an initiator to ethylene or propylene. The initiator is a molecule that readily dissociates into a free radical. A common one is benzoyl peroxide, which dissociates as... 

Accdy to Bolt (Ref 1), ethylene (5.6 moles) was gradually introduced into a 2600-ml autoclave contg 17.6 moles carbon tetrachloride and 0.45 moles benzoyl peroxide, serving as reaction initiator. The pressure was kept below 2500psi. After about 2 hours an expin occurred at 67°, discharging most of the reactants thru the ruptured safery disk... 

In 1838 Regnault [15] reported that vinylidene chloride could be polymerized. In 1839 Simon [16] and then Blyth and Hofmann (1845) [17] reported the preparation of polystyrene. These were followed by the polymerization of vinyl chloride (1872) [18], isoprene (1879) [19], methacrylic acid (1880) [20], methylacrylate (1880) [21], butadiene (1911) [22], vinyl acetate (1917) [23], vinyl chloroacetate [23], and ethylene (1933) [24]. Klatte and Rollett [23] reported that benzoyl peroxide is a catalyst for the polymerization of vinyl acetate and vinyl chloroacetate. 

In general, there are two distinctively different classes of polymerization (a) addition or chain growth polymerization and (b) condensation or step growth polymerization. In the former, the polymers are synthesized by the addition of one unsaturated unit to another, resulting in the loss of multiple bonds. Some examples of addition polymers are (a) poly(ethylene), (b) poly(vinyl chloride), (c) poly(methyl methacrylate), and (d) poly(butadiene). The polymerization is initiated by a free radical, which is generated from one of several easily decomposed compounds. Examples of free radical initiators include (a) benzoyl peroxide, (b) di-tert-butyl peroxide, and (c) azobiisobutyronitrile. 

In the lab of the California Res Corp, Richmond, Calif an expln occurred quite suddenly at 67° >2500 psi after heating ca 2hrs a mixt of CC14, C2H4 a catalytic amt of benzoyl peroxide in a std lab autoclave(Ref 7). Two other examples of uncontrolled reactions between ethylene 8i CCl4, which resulted in violent explns, occurred in a... 

Our own studies of the copolymerization of tetrachloroethylene with ethylene showed that besides telomerization, copolymerization occurs simultaneously. The influence of the experimental variables (pressure, ratio of the monomers, structure and concentration of the initiator, temperature, and time) were studied. As catalysts azoisobutyrodinitrile, fert-butylperoxyisopropyl carbonate, benzoyl peroxide, cyclohexylperoxy carbonate and tert-h xty peroctoate were used. The reactive ratio rx... 

Carbon Tetrachloride and Ethylene. Explosion can result from heating a mixture with a small quantity of benzoyl peroxide.8... 

Benzoyl Peroxide and Ethylene. Mixtures of ethylene and carbon tetrachloride can explode at elevated temperatures on initiation with benzoyl peroxide.3... 

C. cobalt (II) sulfide, ethylene glycol, benzoyl peroxide, ammonium chloride... 

Radical transfer reactions involving poly ethers of the poly (ethylene oxide) type are well known (7). Heating polyethylene glycols of various molecular weights at 140 °C. with dicumyl peroxide for 2.5 hours has resulted in a gel fraction explained by transfer at the a-carbon followed by combination of the polymer radicals. Further, poly (ethylene oxide) dissolved in MMA and heated in the presence of benzoyl peroxide results in grafted copolymer. 

Two of the polystyrene samples were benzoyl peroxide-initiated commercial materials one of these had been on the shelf for over twenty years. The poly (n-butyl methacrylate) and the poly (vinyl chloride) were also commercial materials. The poly (methyl methacrylate) and the third polystyrene sample were prepared under nitrogen from freshly distilled monomers by bulk initiation with azobisisobutyronitrile (AIBN). Each of the above samples was purified by two reprecipitations from tetrahydrofuran solution with methanol and dried in vacuum at 65 °C. for at least 24 hours. The poly (ethylene terephthalate) was a sample of 5-mil Mylar Type A sheet which had been cleaned by detergent washing and water rinsing, followed by vacuum-drying at room temperature for 16 hours. 

A further extension of the principle of polymerization through ethylenic unsaturation allows copolymers to be made with the chemically similar organic substances. For example, methylallyldichloro-silane may be hydrolyzed to the corresponding diol and mixed with monomeric methyl methacrylate, and the mixture polymerized to a homogeneous solid by heating with benzoyl peroxide as a catalyst. 

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