Initiator dicumyl peroxide

LDPE was functionalised in the bulk through dicumyl peroxide-initiated grafting of dibutyl maleate and vinyltrimethoxysilane in the temperature range from 140 to 200 °C (327). 

Thermoplastic elastomers containing PET (50 wt%), compatibilizer (glycid-yl methacrylate grafted rubber or glycidyl methacrylate containing copolymer, 30 wt%) and various rubbers (20 wt%) were produced by melt blending with and without dynamic curing (dicumyl peroxide-initiated) [118]. 

Another vulcanizing agent for diene rubbers is m-phenylenebismaleimide. A catalytic free-radical source such as dicumyl peroxide or benzothiazyldisulfide (MBTS) is commonly used to initiate the reaction [61]. Phenolic curatives, benzoquinonedioxime, and m-phenylenebismaleimide are particularly useful where thermal stability is required. 

The regeneration of nitroxyl radical from the product of the reaction of nitroxyl radical with the alkyl macroradical was proved in the following experiments [51]. The nitroxyl radical and initiator (dicumyl peroxide) were introduced in a PP powder and this sample was heated to T= 387 K in an argon atmosphere. The concentration of nitroxyl radical was monitored by the EPR technique. The nitroxyl radical was consumed in PP with the rate of free radical generation by the initiator (see Figure 19.3). Dioxygen was introduced in the reactor after the nitroxyl radical was consumed. The generation of peroxyl radicals induced the formation of nitroxyl radicals from the adduct of the nitroxyl radical with the PP macroradical. 

As initiators, common peroxides, such as dicumyl peroxide, di-benzoylperoxide can be used, but also photo initiators have been reported. Photoinitiating systems are the combinations of benzo-phenone with amines, such as n-butylamine, trimethylamine and triethylamine (43). 

A binder was obtained from an epoxynovolak resin, BPA/DC, BMI, dicyclopenta-diene, Zn acetate and dicumyl peroxide [94]. In a similar composition, BPA/DC prepolymer was used as curing and cyclotrimerization initiators and catalysts, catechol, triethylenediamine, Zn acetate and benzoyl peroxide are mentioned [95], Other compositions contain A1 acetylacetonate and a silicone resin [96], p-toluenesulfonic acid monohydrate and Zn octoate (for rapid curing) [97], or dicumyl peroxide and Zn octoate [98]. 

Table II shows molecular weight distributions of products from monomer mixtures A and B using 3% dicumyl peroxide as initiator. The molecular weight distributions of the products from the six polymerizations are 3 or less. When, however, the percent of dicumyl peroxide was decreased in the reaction mixture, considerably wider molecular weight distributions resulted (Table III). With less initiator, the chains grow longer and terminate more often by chain transfer.

The results evolved from the data obtained on polymerizations initiated by 2% dicumyl peroxide are shown in Table XII. 

Recent investigations in our laboratory involve the controlled radical polymerization of styrene, initiated by dicumyl peroxide 8 in the presence of Tempo [71,72]. Molecular weights are obtained in the range 2500-300000 with narrow polydispersity (Mw/Mn = 1.5). From such capped Tempo polystyrene 9, polysty-rene-6-chloromethylstyrene (PS-6-PCMSty) [171], PS-h-PBd and PS-h-PBd- -PS block copolymers are prepared with Mw = 50000 and Mw/Mn = 1.5 [72] ... 

The heat and ozone resistant [126] EPR was made by incorporating acrylic rubber, dicumyl peroxide, triaUyl cyanurate, ZnO and carbon-black into the matrix. Triallyl cyanurate increases the crosslinking efficiency probably due to an addition reaction between polymeric and aUyl radicals and leads to stable chemical crosslinks. Thus ozone because there is no unsaturation cannot initiate a degradation reaction. Digteva et al. [127] prepared sealants for use at high temperature by adding aromatic diaminodisulfide, MgO, ZnO and carbon black in EPR. The aromatic diaminodisulfide is an antiozonant and functions both as an antioxidant and a... 

Interesting possibilities for the synthesis of new types of polysaccharide derivatives are offered by the reaction of addition to double bonds, which proceeds by a free-radical mechanism. The presence of initiators of free-radical polymerization (benzoyl peroxide, tert-butyl peroxide, dicumyl peroxide, dinitrile of azodiisobutyric acid), also irradiation with ultraviolet light, has effected the addition to 5,6-cellulosene of chloroform, carbon tetrachloride, methylmonochloroacetate, dimethyl-phosphite and other compounds that decompc under the conditions of a reaction with the formation of free radicals (45,46). The reaction proceeds as follows ... 

Among the most common free radical initiators are benzoyl peroxide, fert-butyl hydroxyperoxide, fert-butyl peroxide, dicumyl peroxide, 2,2 -azobisisobutyronitrile (AIBN), potassium persulfate, etc. 

Elastomers must be crosslinked to hold their final form. The crosslinking reaction takes place through generation of free radicals that promote bonding at sites of unsaturation. The most common crosslinking agents for this include reactive peroxides, such as dicumyl peroxide, diacetyl peroxide, di-tert butyl peroxide, and others. Since each has a different temperature at which thermal decomposition initiates, curing conditions vary with the peroxide type. 

Azonitriles have generally been considered to be cleaner initiators in the sense of being devoid of chain transfer however, recent research w ork indicates this is not true. Other initiators/chain-transfer agents include /-butyl peroxide, cumyl peroxide, lauryl peroxide, benzoyl peroxide, /-butyl hydroperoxide, cumyl hydroperoxide, dicumyl peroxide, and persulfate the half-lives of these initiators are given in Table 4.2 [185],... 

External initiators most frequently used in the investigation of the oxidation mechanism and the kinetics of polymers degradation are benzoyl peroxide [Refs. 260, 261, 364, 453, 512—517, 614], dicumyl peroxide [40, 364, 610], terf-butyl peroxide [633] and 2,2-azo-bis-isobutyronitrile [Refs. 48, 191, 196, 364, 403, 417, 426],... 

The temperature of an initiator depends on the rate of decomposition as reflected in its half-life. A good rule-of-thumb in this regard is a ti/2 of about 10 h at the particular reaction temperature (Table 6.2). The practical use temperature ranges of some common initiators are diacetyl peroxide 70-90°C, dibenzoyl peroxide 75-95°C, dicumyl peroxide 120-140°C, and AIBN 50-70°C (Odian, 1991). 

For PE, the relationship between grafting efficiency and cross-linking of chains can be controlled by varying the concentration ratio of the initiator to the monomer (3). For example, no cross-linking was detected when diethylmaleate (DEM) was grafted to PE as initiated by dicumyl peroxide (DCP) if the ratios (DCP) [DEM] < 0.09. A positive effect on grafting is caused by lower molecular weight of PO (lower melt viscosity) (3). 

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