Cross-linking dicumyl peroxide

For peroxide cross-linking, organic peroxides, such as dicumyl, di-t-butyl, and benzoyl peroxides, are used in amounts 1 to 3 phr (parts per hundred parts of rubber). Typical cure cycles are 5 to 10 min at temperatures 115 to 170°C (239 to 338°F), depending on the type of peroxide used. Each peroxide has a specific use. A postcure is recommended to complete the cross-linking reaction and to remove the residues from the decomposition of peroxide. This improves the long-term heat aging properties.62... 

For many years chlorinated polyethylenes have been used mainly as additives to PVC. However in the 1970s rubber grades were introduced (e.g. Hostaprene—Hoechst, Dow CM—Dow Chemical). The polymers are cross-linked by peroxides, such as dicumyl peroxide, and plasticized with plasticizers of the types commonly used with PVC, e.g. diisooctyl phthalate. The vulcanizates are claimed to provide heat resistance in air and oil at temperatures up to 150 C at a lower cost than possible with older established polymers. 

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. 

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). 

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. 

Cross-Linking of Ethylene-Propylene Copolymer Rubber with Dicumyl Peroxide-Maleic Anhydride... 

Ethylene-propylene and silicone rubbers are crosslinked by compounding with a peroxide such as dicumyl peroxide or di-t-butyl peroxide and then heating the mixture. Peroxide cross-linking involves the formation of polymer radicals via hydrogen abstraction by the peroxy radicals formed from the decomposition of the peroxide. Crosslinks are formed by coupling of the polymer radicals... 

The most common compound for peroxide cross-linking of PE in the wire and cable industry is dicumyl peroxide (DCP), which decomposes at 120-125°C (248-257°F), generating free radicals needed for the process plus by-products (carbinol, acetophenone, and methane). The production line for continuous vulcanization of wire and cables by peroxide must be about 200 m (61 ft) long. 2 The plant space required for radiation cross-linking using... 

The two component FID (and corresponding superposed broad line spectra), for some polydimethylsiloxanes (PDMS) arises from crystalline and amorphous components. Polymers highly crosslinked with dicumyl peroxide exhibit quite similar data, but after the removal of all unlinked material, the FID consists only of a single component, indicating an almost complete reduction in crystallinity due to the cross-linking 84). 

Poly(vinyl ethyl ether) is soluble in ethanol, acetone and benzene. It is a rubbery product which may be cross-linked by heating with dicumyl peroxide. Polyfvinyl isobutyl ether), has a glass transition temperature of —5°C. It has been used as an adhesive for upholstery, cellophane and adhesive tape. 

Table 11. Cross-linking density of some EPTMs, EPDMs and EPM cured with dicumyl peroxide (DCP)... 

The results obtained, when dicumyl peroxide is used as curing agent (Table 19), indicate that 13,5-hexatriene (HTl) and 2,4,6-octatriene (OTI)-based copolymers can be easily cross-linked. 

Figure 8.29 plotted against Gg for three rubbers [polybutadiene (PB), styrene-butadiene copolymer (SBR), and natural rubber (NR)] at different stages of cross-linking by (O) dicumyl peroxide and ( ) sulfur. (From Ref. 44.)... 

The reactivity of EPTMs in radical curing, predicted by these calculations, has been confirmed directly by cross-linking density measurements (Table 11) also carried out on EPM and some EPDMs vulcanized with dicumyl peroxide at 145 °C. 

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). 

An interesting, indirect application of the statistical theory to filled rubbers has been published by Wolff (/33). In recent years increasing use has been made of oscillating disc rheometers to follow the course of vulcanization. These instruments operate at low frequencies and at vulcanization temperatures, so that torque recorded at full cure is a good measure of an equilibrium she ur modulus and hence proportional to V. Wolff finds for polymers filled with furnace blacks and cross-linked with dicumyl peroxide ... 

Polybutadiene is readily cross-linked by heating with 1% dicumyl peroxide for 10 min at 145°C. If the product is first extracted with C2CI4 to remove any non-cross-linked material and then placed in eontact with WCl6/EtA.lCl2/EtOH in C2CI4 at 45°C, it rapidly goes into solution (Hummel 1970 Kumar 1981). An added acyclic olefin assists this process but is not essential. It is clear that the network can be readily broken down by the occurrence of either intramolecular or intermolecular metathesis reactions. 

A = anionic R = radical E = emulsion polymerization, ° 3-C denotes hex-3-ene, etc. W(=CHCMe2Ph)(=NAr)[OCMe(CF3)2]2- Partially aralkylated by reaction with 4-chlorotoluene/dicumyl peroxide. Cross-linked by partial bromination with NBS/AIBN followed by reaction with BrMg(CH2) MgBr (n = 4, 6). 1,10-di(9-borabicyclononane)-dec-5-ene. Cross-linked by heating with dicumyl peroxide. 

Figure 4. Aliphatic region of natural rubber cross-linked with dicumyl peroxide. Spectra were taken under normal FT conditions. The loading of peroxide is Indicated at the high field side of the spectra.

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