Peroxide induced cross-linking

Perkalink . [Akzo] Cyanuratesormeth acrylates co-agent u> improve effi ciency of peroxide-induced cross-link ipg of rubber sensitizer for radiation cured compds. 

Peroxide-induced cross-links are stable to oxidation, whereas sulfur cross-links may oxidize, leading to cross-link rupture. Peroxide-cured vulcanizates exhibit higher compression set resistance than their counterpart sulfur-cured vulcanizates. Peroxide vulcanizates generally have better low-temperature flexibility than do sulfur vulcanizates. 

Zhou, W., Zhu, S. ESR study of peroxide-induced cross-linking of high density polyethylene. Macromol. (1998) 31, pp. 4335-4341... 

It is clear from these results that the formation of ethylenic unsaturation, peroxides, and cross-linked gel are primary processes associated with the shear-induced mechanochemical reactions occuring during the first minute of processing. The lower the temperature, the higher the... 

SiHcone mbber has a three-dimensional network stmcture caused by cross-linking of polydimethyl siloxane chains. Three reaction types are predominantiy employed for the formation of siHcone networks (155) peroxide-induced free-radical processes, hydrosdylation addition cure, and condensation cure. SiHcones have also been cross-linked using radiation to produce free radicals or to induce photoinitiated reactions. 

Exposure of protein amino groups to MDA (formed by the degradation of lipid peroxides) or to oxygen radicals directly, generated by transition metals and hydrogen peroxide, induce fluorescence indistinguishable from that attributed to Amadori-adduct formation (Chio and Tappel, 1969), and leads to the formation of cross-links (Lunec a al., 1985). 

Methods for detecting whether peroxy compound have been used for cross-linking elastomers have been reviewed. An important application of dialkyl peroxides is as initiators of cross-linking and graft polymerization processes. The success of both processes depends on the ability of the peroxide to produce free radicals and the ability of the free radicals for H-abstraction from a relevant donor substrate. A method for evaluating this ability consists of inducing thermal decomposition of the peroxide dissolved in a mixture of cyclohexane and MSD (225). The free radical X" derived from the... 

Articles in which glass fibers are imbedded to improve impact strength often are made by mixing the fibers with an ethenylbenzene (styrene) solution of a linear glycol (usually l,2-propanediol)-butenedioic anhydride polyester and then producing a cross-linked polymer between the styrene and the double bonds in the polyester chains by a peroxide-induced radical polymerization (Section 29-6E). 

Lipid peroxidation is one of the major sources of free-radical mediated injury that directly damages membranes and generates a number of secondary products. In particular, markers of lipid peroxidation have been found to be elevated in brain tissues and body fluids in several neurodegenerative diseases, and the role of lipid peroxidation has been extensively discussed in the context of their pathogenesis. Peroxidation of membrane lipids can have numerous effects, including increased membrane rigidity, decreased activity of membrane-bound enzymes (e.g., sodium pumps), altered activity of membrane receptors, and altered permeability [Anzai et al., 1999 Yehuda et al., 2002], In addition to effects on phospholipids, lipid-initiated radicals can also directly attack membrane proteins and induce lipid-lipid, lipid-protein, and protein-protein cross-linking, all of which obviously have effects on membrane function. 

De Vos et al. (1989) suggest that the copper-induced damage to the permeability barrier in roots of Silene cucubalus is caused by a direct metal action on both membrane lipids and thiols. They propose that the first damaging effects of copper ions is the oxidation and cross-linking of membrane protein sulphydryls. However, they also adjudge an important role to the copper induced membrane lipid peroxidation, possibly due to direct free radical formation in the membrane this effect could be enhanced by a depletion of thiols such as glutathione which results in a concomitant decrease of the cellular defence system against free radicals. 

In primary rahhit proximal tuhular (RPT) cells cisplatin exposure resulted in an inhihition of DNA synthesis, which is most likely related to the primary anti-tumorigenic mechanism of this compound i.e. DNA inter and intra strand cross linking [117]. RNA and protein synthesis were decreased in RPT cells and quiescent LLC-PK cells upon cisplatin exposure [117, 118]. Other effects of cisplatin on cultured RPT include a decrease in glucose uptake, an inhihition of Na -K ATPase and alterations in total glutathione content [117]. In the normal rat kidney (NRK) cell hne cisplatin (IpM for 48h) induced a marked increase in the level of lipid peroxides [119]. 

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