Cooling peroxide-initiated

Among polymers of methacrylic esters, poly(methyl methacrylate) is the most important one industrially. Most of it is prepared by free-radical polymerizations of the monomer and a great deal of these polymerizations are carried out in bulk. Typical methods of preparation of clear sheets and rods consist of initial partial polymerizations in reaction kettles at about 90 °C with peroxide initiators. This is done by heating and stirring for about ten minutes to form syrups. The products are cooled to room temperature and various additives may be added. The syrups are solutions of about 20% polymer dissolved in the monomer. They are poured into casting cells where the polymerizations are completed. The final polymers are high in molecular weight, about 1,000,000. 

As is the case with simple paraffins, polyethylene may be halogenated. Chlorinated polyethylene is available commercially but has achieved little importance. Polyethylene may be chlorinated in solution, using solvents such as hot carbon tetrachloride, chloroform and chlorobenzene. Alternatively, a suspension of the polymer may be chlorinated suspensions are prepared either by cooling a solution of polymer in carbon tetrachloride or by polymerizing ethylene in the presence of water. The chlorination of polyethylene is usually conducted at temperatures between 45°C and 75°C and is initiated by light or peroxides. Initiation involves production of chlorine atoms which then propagate the following chain reaction ... 

Free cydohexene from peroxides by treating it with a saturated solution of sodium bisulphite, separate, dry and distil collect the fraction, b.p. 81-83°. Mix 8 -2 g. of cycZohexene with 55 ml. of the reagent, add a solution of 15 mg. of osmium tetroxide in anhydrous butyl alcohol and cool the mixture to 0°. Allow to stand overnight, by which time the initial orange colouration will have disappeared. Remove the solvent and unused cydohexene by distillation at atmospheric pressure and fractionate the residue under reduced pressure. Collect the fraction of b.p. 120-140°/15 mm. this solidifies almost immediately. Recrystallise from ethyl acetate The yield of pure cis-l 2 cydohexanediol, m.p. 96°, is 5 0 g. 

Ferrovanadium can also be prepared by the thermite reaction, in which vanadium and iron oxides are co-reduced by aluminum granules in a magnesite-lined steel vessel or in a water-cooled copper cmcible (11) (see Aluminumand aluminum alloys). The reaction is initiated by a barium peroxide—aluminum ignition charge. This method is also used to prepare vanadium—aluminum master alloys for the titanium industry. 

High molecular weight polymers are produced by an adiabatic bulk polymerisation process ° using di-tert-butyl peroxide (0.02%) and 2,2 -azo-bisdi-isobutyronitrile (0.01%) as initiators and pressurised with N2. Heating to 80-90°C causes an onset of polymerisation and a rapid increase in temperature. After the maximum temperature has been reached the mass is allowed to cool under pressure. A typical current commercial material (Luvican M.170) has a A -value of about 70 (as assessed in a 1% tetrahydrofuran solution). 

Formaldehyde, benzaldehyde and aniline react violently with 90% performic acid (Ref 1). An unspecified organic compd was added to the acid, and soon after the initial vigorous reaction had subsided, the mixt expld violently (Ref 3). Reaction with aikenes is vigorously exothermic, and adequate cooling is necessary. Reactions with performic acid can be more safely accomplished by the slow addition of hydrogen peroxide to a soln of the compd in formic acid (Ref 4)... 

Vinyl Acetate CH3COOCH=CH2 OH compds, HCN, Halides, Halogens, Mer-cap tans, Amine, Silanes Oxygen Vap in Air 2.6 to 13.4% > Ambient > Ambient Inhibitor—Methyl Ether of Hydroquinone or 3-5ppm Diphenylamine. Store in a dry, cool place shield from light impurities 20.9-21.5 402 427 Free-radical polymerization initiated by Benzoyl Peroxide... 

A terpene inhibitor is usually added to the monomer to prevent spontaneous polymerisation, and in its absence, the monomer will spontaneously explode at pressures above 2.7 bar. The inhibited monomer will explode if ignited [1]. Explosion under thermal initiation is now held to be a disproportionation, that to tetrafluo-romethane and carbon gives 3.2 kJ/g, the same energy as black powder [3], Liquid tetrafluoroethylene, being collected in a liquid nitrogen-cooled trap open to air, formed a peroxidic polymer which exploded [2]. 

A. 3,5-Dichlorosulfanilamide. In a 2-1. round-bottomed flask, fitted with a two-holed stopper carrying a mechanical stirrer and a thermometer, are placed 50 g. (0.29 mole) of sulfanilamide and 500 ml. of water. About 50 ml. of a 500-ml. portion (approximately 6 moles) of pure concentrated hydrochloric acid is added, and the mixture is stirred until a clear solution results (Note 1). The remainder of the 500 ml. of hydrochloric acid is then added. If the internal temperature does not rise to 45°, the stirred solution should be warmed gently with a free flame until this temperature is reached. At this point 65 g. (59 ml., 0.58 mole) of 30% hydrogen peroxide (sp. gr. 1.108) is added and rapid stirring is initiated (Note 2). The heat of reaction causes a progressively faster rise in temperature. After 5 minutes the solution fills with a white precipitate which increases rapidly in amount and becomes delicately colored. When the temperature has reached 60°, about 10 minutes after adding the peroxide (Note 3), any further rise is preferably prevented by judicious cooling (Note 4). The reaction is allowed to proceed for 15... 

The result of this change in mechanism is that the major products at high temperatures are olefins and hydrogen peroxide and their secondary decomposition products, which of course include water. The relatively unstable alkyl hydroperoxide produced by the low temperature chain is replaced by the much more stable hydrogen peroxide. The result is that the secondary initiation, responsible for the cool flames, is replaced by a much slower initiation—the second-order decomposition of hydrogen peroxide (Reaction 6). 

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