Grafting, high-temperature

Because high temperatures are required to decompose diaLkyl peroxides at useful rates, P-scission of the resulting alkoxy radicals is more rapid and more extensive than for most other peroxide types. When methyl radicals are produced from alkoxy radicals, the diaLkyl peroxide precursors are very good initiators for cross-linking, grafting, and degradation reactions. When higher alkyl radicals such as ethyl radicals are produced, the diaLkyl peroxides are useful in vinyl monomer polymerizations. 

Issues to be considered in selecting the best stabilizing system are polymeric chain branching which increases with high temperature and the presence of some stabilizers, polydispersity of the particles produced, and grafting copolymerization, which may occur because of the reaction of vinyl acetate with emulsifiers such as poly(vinyl alcohol) (43,44). 

Grafting is most commonly carried out with peroxides that arc sources ol t-alkoxy radicals e.g. 22-25). At the high temperatures usually used, the extent of... 

At this point, we can schematically represent the structure of Cr(II) sites as (SiO)2Cr L , where L represents a weak ligand (oxygen of a SiOSi bridge) and n is a not fully known figure which increases upon activation at high temperature. The adsorption of CO at room temperature on grafted Cr(II) sites... 

Similar studies were undertaken as a comparison in the styrenic systems, although in these systems we also were able to compare the graft systems to diblock systems of similar composition. DSC also shows a depression of the high temperature Tg for all of the styrenes for the IK graft systems. The 5K systems showed a smaller depression but still a slight lowering of the Tg (Table VIII). Clearly, the t-butylstyrene system is most influenced, as anticipated. 

Two different approaches have been used to graft molybdenum on alumina, namely, either a two-step process involving gas-phase impregnation and further decomposition at high temperature (GPID) or the direct contact of [Mo(CO),5] vapor with the alumina support placed in a hot zone so as to achieve its decomposition. All of the relevant studies point to the existence of a close relationship between the OH group density on the support and the amount of deposited molybdenum as well as the chemical nature of such deposits. Hence, we successively deal with three types of alumina highly, partially and fully dehydroxylated surfaces. 

Use of Crosslinked VC/PE Graft Copolymers for Cable Insulation. At high temperatures, plasticized PVC cable insulations show a rather high flow. This should be improved by crosslinking of the thermoplastic insulation material. Unfortunately, PVC is not easily cross-linkable by chemical agents. The presence of about 503 of grafted or... 

The surface of polymeric materials such as polypropylene (PP), PS, polyacrylonitrile (PAN), and nylon was oxidized by immersing them in aqueous solution of oxidizing agents such as potassium peroxy disulfate under nitrogen purging at high temperatures [14]. Graft polymerization of water-soluble monomers such as AAm, methacrylic acid, and 3-aminopropyl methacrylate has been frequently performed in aqueous solution with the use of ceric ion, for instance, at... 

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