Dicumyl peroxide stability

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. 

Figure 1. Effect of dicumyl peroxide (DCP) and processing conditions (excess, OM, and restricted, CM, oxygen amount) on melt stability of PP.

A rubber mixture contains ethylene-propylene rubber, BPA/DC, CaC03, ZnO, sulfur, dicumyl peroxide and mineral oil. The final product has elevated thermal stability [147]. 

Reactivity with Aromatic Nitrones. Rubber bound AO 179 based on 1,3-cycloaddition of aromatic nitrones (180) to C = C double bonds of IR or BR were formed during the vulcanization process [236]. In IR, 50-89% of nitrones was bound-in in the dicumyl peroxide vulcanizate, 39-85% in the tetramethylthiuram disulfide vulcanizate. Pendant stabilizing moieties are attached to the rubber chain by means of the isoxazolidine moiety. Crosslinks are formed with bis-nitrones. It should be mentioned that aromatic nitrones unfavourably influence the scorch time of the both conventional and sulfurless IR or BR compounds. Aminic stabilizer 179a is an effective but discoloring and staining AO. Unhindered... 

Several companies have experimented with the use of vinyl oiganosUanes as cross-linking agents. For example, 2 percent of vinyl trimethoxy silane is first activated by 0.1 percent of dicumyl peroxide and grafted onto the thermoplastic polymer. The system is kept dry to stabilize the methoxy groups. After melt processing, the solid product is exposed to moisture to hydrolyze the methoxy groups, which then condense with each other to form cross-links. 

Tensile properties of different EVA/ATH formulations are summarized in Table 4.3. The basic formulation contained 160phr of ATH, 1 phr stabilizer, and variable amounts of monomeric and oligomeric silanes and peroxide. A corotating twin-screw extruder was used to produce sheets for the tests. SUane content is based on filler, the silane was preblended with the EVA, dicumyl peroxide (DCP) and Irganox 1010 (phenolic stabilizer, Qba) were used as peroxide and stabilizer, respectively. A control without silane is not included since it leads to scorch. 

Low amounts of stabilizer are necessary for improving the stability of polymers [06C1]. The most used polymer, polyethylene, needs antioxidants in its product formulation, even though it is saturate polymer and the oxidation in any conditions starts more slowly than in many other polymer materials. A comparative study on the effect of two additives (hydrolysis-conditioned phosphate and IRGANOX 1076) on the thermal stability of medium density polyethylene (MDPE) and low density polyethylene (LDPE) (Fig. 71) illustrates the performances of material modified with carbon black (CB) and dicumyl peroxide (DCP), respectively [02F1]. This figure demonstrates that the same antioxidants promote differently thermal protection in the direct relation with material formulation. 

Crosslinking of many commercial thermoplastics is conducted with reactive peroxides, including dicumyl peroxide, benzoyl peroxide, and many others, all of which have different activation temperatures. At the crosslinking initiation temperature, tire peroxide decomposes and forms free radicals that react with unsaturated end groups on the polymer chains, thus forming chemical crosslinks between chains. For thermoplastic addition, stability of the peroxides is increased for storage and handling by incorporation into master batches that may include waxes, clay, fatty acids, or resins. 

Peroxides cure by decomposing on heating into oxy radicals which abstract a hydrogen from the elastomer to generate a polymer radical. The polymer radicals then react to form carbon-carbon crosslinks. With imsaturated elastomers, this occurs preferentially at the site of allylic hydrogens. The rate of crosslinking is directly proportional to the rate of decomposition of the peroxide. Cure rates and curing temperatures therefore depend on the stability of the peroxide, which decreases in the order dialkyl > perketal > perester or diaryl. The most commonly used of these crosslinkers is dicumyl peroxide. 

EFFECT OF DICUMYL PEROXIDE ON MECHANICAL STABILITY TIME OF CONCENTRATE LATEX... 

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