Chlorobenzoyl peroxide initiator

Another differential reaction is copolymerization. An equi-molar mixture of styrene and methyl methacrylate gives copolymers of different composition depending on the initiator. The radical chains started by benzoyl peroxide are 51 % polystyrene, the cationic chains from stannic chloride or boron trifluoride etherate are 100% polystyrene, and the anionic chains from sodium or potassium are more than 99 % polymethyl methacrylate.444 The radicals attack either monomer indiscriminately, the carbanions prefer methyl methacrylate and the carbonium ions prefer styrene. As can be seen from the data of Table XIV, the reactivity of a radical varies considerably with its structure, and it is worth considering whether this variability would be enough to make a radical derived from sodium or potassium give 99 % polymethyl methacrylate.446 If so, the alkali metal intitiated polymerization would not need to be a carbanionic chain reaction. However, the polymer initiated by triphenylmethyl sodium is also about 99% polymethyl methacrylate, whereas tert-butyl peroxide and >-chlorobenzoyl peroxide give 49 to 51 % styrene in the initial polymer.445... 

The effect of inhibitor, peroxide, initiator and amine accelerator on the rate of polymerization of poly(methyl methacrylate) slurries has been studied ( 5, O. Time required to reach the exotherm indicates aromatic peroxides, especially -chlorobenzoyl peroxide, to be the most efficient initiators. Although polymerization in the presence of this compound and N,N-dimethyl-2 toluidine (DMPT) is more rapid initially, it is slower after the exotherm than is a system employing BP-DMPT. Polymerization using the latter initiator-accelerator gives resins with lower residual monomer. 

DI-(4-CHLOROBENZOYL) PEROXIDE or DI-(p-CHLOROBENZOYL) PEROXIDE or p,p -DICHLOROBENZOYL PEROXIDE (94-17-7) Explosive solid or paste. Thermally unstable above 80°F/27 C explosion can be caused by exposure to direct sunlight, hot surfaces, or heat abovel00°F/38°C. Highly toxic chlorinated biphenyls are emitted in fire. A powerful oxidizer. Reacts violently with many materials, including reducing agents, combustible materials, metallic powders, organic substances, polymerization initiators, thiocyanates, or contaminants. Explosive polymerization may be initiated by shortwave radiation. 

Figure 7.2 Relationship between initiator concentration and polymerization rate for different initiators A, bis(p-chlorobenzoyl)peroxide B, benzoyl peroxide C, acetyl peroxide in dimethylphthalate D, lauroyl peroxide E, myristoyl peroxide F, caprylyl peroxide G, bis(2,4 dichlorobenzoyl) peroxide. [A.I. Lowell and J.R. Price, J. Poly. Sci, 43, 1 (1996). With permission.]... 

---