Hydroperoxides polymerization agents

Polymer immobilization. Mo-peroxide, 427 Polymerization agents, 621, 622 peroxide value, 661, 662 peroxycarboxyUc acids, 698 radical polymerization, 697, 707 styrene, 697, 720 sulfonyl peroxides, 1005 thermochemistry, 155 Polymers aging, 685 autoxidation, 623 hydroperoxide determination, 685 Poly(methacrylonitrile peroxide)... 

Derivative Formation. Hydrogen peroxide is an important reagent in the manufacture of organic peroxides, including tert-huty hydroperoxide, benzoyl peroxide, peroxyacetic acid, esters such as tert-huty peroxyacetate, and ketone derivatives such as methyl ethyl ketone peroxide. These are used as polymerization catalysts, cross-linking agents, and oxidants (see Peroxides and peroxide compounds). 

Hydroperoxides are generally used with reducing agents, eg, iron salts, in redox emulsion polymerization systems. 

Simplified nitrile mbber polymerization recipes are shown in Table 2 for "cold" and "hot" polymerization. Typically, cold polymerization is carried out at 5°C and hot at 30°C. The original technology for emulsion polymerization was similar to the 30°C recipe, and the redox initiator system that allowed polymerization at lower temperature was developed shortiy after World War II. The latter uses a reducing agent to activate the hydroperoxide initiator and soluble iron to reactivate the system by a reduction—oxidation mechanism as the iron cycles between its ferrous and ferric states. 

For chromatographic sorbents it is necessary that the polymeric cover be uniformly distributed over the silica surface and chemically coupled to it. The appropriate introduction of the initiator is one of the decisive steps of this task. The first method (binding to the surface) increases the yield of grafted polymer. However in this case a large amount of homopolymer is formed. This disadvantage could be prevented by the application of hydroperoxide initiators in combination with the proper redox-agents [78-81],... 

In the first step a rubbery polymer latex is prepared by emulsion polymerization of styrene and butadiene, the styrene being in an amount of 25%. Divinylbenzene is added as crosslinking agent in an amount of 1%. Diphenyl oxide sulfonate is used as emulsifier in aqueous solution and sodium formaldehyde sulfoxylate acts as a buffer in order to reach a pH of 4. As radical initiator, cumene hydroperoxide is used and the polymerization is conducted 70°C for 9 h. The end of the reaction period is detected as no further pressure drop is observed due to the consumption of butadiene. 

Redox initiators. Free radicals are produced in redox initiators by one-electron transfer reactions. This t T)e of initiator is particularly useful in initiation of low-temperature polymerization and emulsion polymerization. Some typical examples are persulfate + reducing agents hydroperoxides -i- ferrous ion. 

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