Butadiene rubber peroxide-curing

The elastomeric sealing components of the metering valve are particularly critical. In those valves used with CFC propellants, the elastomeric seals have typically been formed from an acrylonitrile/butadiene rubber, which has been cured with sulfur. These rubber seals may not be fully compatible with HFA propellants hence, alternative elastomeric materials have been used. These materials include peroxide-cured acrylonitrile/ butadiene, ethylene-propylene diene monomer (EPDM), and chloroprene and thermoplastic elastomers (TPE). The elastomeric materials used to form the dynamic seals around the stem and the static gasket seal between the can and valve may differ based on the required properties of the rubber for the specific function of the seal. The most important characteristics of the elastomeric seals... 

Synonyms VBR Vinyl butadiene rubber Uses Thermosetting resin for wire coating, coatings coagent processing aid EPDM peroxide-cured modifier rubber in tire mfg. Trade Name Synonyms Buna VI47-0 T[Bayer AG http //WWW. bayer-ag. de, http //www. bayer. com-, Bayer/Fiber, Add its.. Rubber http //www.bayerus.com]-. Buna VI 47-1 T[Bayer AG http //www.bayer-ag.de-, http //www.bayer.com, Bayer/Fiber, Addits., Rubber http //www.bayerus.com]-. Buna VI 70-0 HM T[Bayer AG http //www.bayer-ag.de-, http //www.bayer.com, Bayer/Fiber, Addits., Rubber http //www.bayerus.com]-. Buna VI 70-1 T[Bayer AG http //www.bayer-ag.de-, http //www.bayer.com-, Bayer/Fiber, Addits., Rubber http //www.bayerus.com]-. Buna VI 80-0 HM T[Bayer AG http //www.bayer-ag.de, http //www.bayer.com-, Bayer/Fiber, Addits., Rubber http //www.bayerus.com]... 

Nitrile polymers are vulcanized in essentially the same manner as styrene butadiene rubber (SBR) and natural rubber. The same ingredients are used, although not necessarily in the same amounts. Sulfur is less soluble in nitrile rubber than in SBR or natural rubber, and smaller amounts are used. A corresponding increase in accelerator is required. Sulfur/accelerator, sulfur donor, and peroxide cures are chosen depending on the ultimate processing methods and applications. 

Styrene-butadiene rubber, SBR, served as polymer I. The IPNs and semi-IPNs were synthesized by thermal polymerization techniques.The SBR for the semi-IPNs of the first kind and for the full IPNs was prepared by dissolving the rubber in benzene, adding the appropriate amount of dicumyl peroxide (Dicup) for crosslinking, and then evaporating the solvent. The SBR was then cured in a compression molding operation at a temperature of 325°F and at a pressure of 40-50 psi for 45 min. See Table 5.3 for levels of crosslinker employed. 

Yin DH, Zhang Y, Zhang YX, Peng ZL, Fan Y, Sun K (2002) Reinforcement of peroxide-cured styrene-butadiene rubber vulcanizates by mathacrylic acid and magnesium oxide. J Appl Polym Sci 85(13) 2667-2676... 

Natural rubber pale crepe was cured in the presence of 0.59 1.0, 2.0, 3.0, U.O, 10.0 and 20.0 parts dicumyl peroxide per h mdred parts of rubber (p.h.r.) at lU5°C for approximately ko minutes. Poly-cis-1, -butadiene samples were cured with 0.5 1.0, 2.0 and U.O p.h.r. dicumyl peroxide under similar conditions. 

The problem of cross-linking or grafting low unsaturated rubbers (e. g. EPDMs or EPTMs) or thermoplastics (e. g. ethylene-butadiene copolymer is fundamentally the same. Radical mechanisms are believed to be operative when peroxides or sulfur-based formulations are used, even though in the latter case ionic mechanisms also seem to contribute to the curing process ... 

Most rubber is based on polymers of isoprene or butadiene and contains many reactive C=C double bonds available for cross-linking. It is cross-linked by sulfur, aided by metal oxides and organic catalysts, producing sulfide cross-links between the polymer chains. Ethylene-propylene rubber is mostly made with several percent of diene ter-monomer to inttoduce C=C double bonds, which can then be vulcanized in the same way. Similarly, butyl rubber is made with a few percent of isoprene comonomer to introduce C=C double bonds and permit sulfur vulcanization. Even saturated elastomers are sometimes cured by sulfur, using peroxides and catalysts to activate C-H bonds, and metal oxides to attack C-Cl bonds. 

Polybutadiene-type resins n. Unsaturated, thermosetting hydrocarbons cured by a peroxide-catalyzed, vinyl-type polymerization reaction, or by sodium-catalyzed polymerization of butadiene or blends of butadiene and styrene. Liquid systems, curable in the presence of monomers, are used for casting, encapsulation, and potting of electrical components, and in making laminates. Molding compounds, often containing fillers and modified with other resins or rubbers, may be compression or transfer molded. Syndiotactic 1,2-butadiene, introduced in 1974 in Japan, is thermoplastic, with semicrystalline nature, with good transparency and flexibility without plasticization. In the presence of a photosensitizer such as p,p -tetramethyl... 

The unmodified PGV and modified MMTs were used as a fillers in ethylene-propylene copolymer EPR and hydrogenated butadiene-acrylonitrile rubber HNBR. The elastomers were cured using dicumyl peroxide DCP. 

Figure 2 illustrates the length-temperature data for one of the elastomers, poly-cis-1, U-butadiene cured with 0.5 p.h.r. dicumyl peroxide, at a series of loads. From the slopes of the straight lines in this plot, the linear thermal expansion coefficients of the strained rubber can be readily obtained. In order to compute the relative energy contribution to rubber elasticity by eq. 6, we need the linear thermal expansion coefficients of the unstrained rubber and the temperature coefficient of the shear modulus. These can be determined by plotting a as a function of the quantity (X -l)/(X +2). If eq. 7 is indeed valid, then one would expect a linear relation. From the intercept and slope of such a plot, values of and dilnG/dT can be easily obtained. 

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