Peroxide, dicumyl

Cross-linking of polyethylene can be accomphshed either chemically or by high energy radiation. Radiation cross-linking is usually accomphshed by x-rays (44) or electrons (45,46). Chemical cross-linking of polyethylene is accomphshed with dicumyl peroxide (47), d4-tert-huty peroxide (48), or other peroxides. Radiation cross-linking (49) is preferred for thin foams, and chemical cross-linking for the thicker foams. 

Substitution reactions on dialkyl peroxides without concurrent peroxide cleavage have been reported, eg, the nitration of dicumyl peroxide (44), and the chlorination of di-/ fZ-butyl peroxide (77). Bromination by nucleophilic displacement on a-chloro- or a-hydroxyalkyl peroxides with hydrogen bromide produces a-bromoalkyl peroxides (78). 

The following commercially available dialkyl peroxides are produced according to equations 24—27 di-Z fZ-butyl peroxide from hydrogen peroxide and sulfated tert-huty alcohol or isobutylene dicumyl peroxide from a-cumyl hydroperoxide and cumyl alcohol, cumyl chloride, and/or a-methylstyrene m- and -di(2-/ f2 -butylperoxyisopropyl)ben2ene [2781-00-2] from tert-huty hydroperoxide [75-91-2] and m- and -di(2-hydroxyisopropyl)ben2ene ... 

ASTM Standard E 755-90, "Standard Test Method for Assay of Dicumyl Peroxide by Liquid Chromatography," in Ref. 253. 

Fig. 13. Relationship of nittile rubber cure systems where DCP is dicumyl peroxide MBTS, benzothiazyl disulfide ZrJDMD, zinc dimethyldithiocarbamate ...

Dicumyl peroxide [80-43-3] M 270.4, m 39-40 . Crystd from 95% EtOH (charcoal). Stored at 0°. Potentially EXPLOSIVE. 

Vulcanised (cross-linked) polyethylene is being used for cable application where service temperatures up to 90°C are encountered. Typical cross-linking agents for this purpose are peroxides such as dicumyl peroxide. The use of such agents is significantly cheaper than irradiation processes for the cross-linking of the polymer. An alternative process involves the use of vinyl silanes (see Section 10.9). 

Polymers containing vinyl side groups may be cured with less reactive peroxides such as dicumyl peroxide and t-butyl peracetate. 

Approximately 5% of radicals undergo cage recombination when dicumyl hyponitrite (35) is decomposed in bulk MMA or S at 60 CC.72 Dicumyl peroxide, the product of cage recombination is likely to be stable under the conditions where hyponitrites are usually employed. Nonetheless, its formation is a concern since... 

Similar blends have been made by cross-linking the E-plastomer with peroxides. This process suffers from an inherent degradation of the iPP by peroxide. In a representative formulation, a mixture of 60 parts of E-plastomer (octene commoner), 15 parts maleated (0.6%) iPP, 25 parts of EPDM, 10 parts of paraffinic plasticizer, 5 parts of dicumyl peroxide, and 1 part of stabilizer was treated at 170°C for 5 min to give a cross-linked blend with Shore A hardness 66, tensile strength 5.5 MPa, and elongation 190%. Similar blends have been made with the incorporation of a limited amount of a SEES polymer to act as a compatibilizer between the E-plastomer and the iPP. 

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. 

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