Thermally induced cross-links

With regard to the type of thermally induced cross-links, the following conclusions may be drawn from our results Formation of C—C bonds can be definitely excluded due to the cleavage observed by aqueous acid. Intramolecular ether bonds within the glucose unit might explain the change in cuprammonium viscosity, but they should be cleaved also by aqueous alkali. The most probable conclusion is, according to our opinion, a formation of intercatenary acetal bonds (12). 

Different thermally induced cross-linking approaches have been investigated, such as the formation of sol-gel networks [93,94] or reactions resulting in poly-imides [95] and maleimides [96]. Thermoset PU have been widely studied for EO applications [92,97]. Zhang et al. synthesized a high /i/Lderived isophorone-derived... 

ASTM D3351 describes the gel count test. Gels are imperfections found in the film, often related to thermally induced cross-linking. In the standard test, a 640 in area of film is examined and the number and size of gels are counted. 

Another method to obtain a uniformly-ordered cholesteric network was applied by Vallerian et al. [15]. They started with a linear cholesteric side-chain polymer which was prepared between glass slides. By surface effects, a Grandjean texture becomes stable. Because the linear polymer additionally contains polymerizable groups, a thermally-induced cross-linking reaction forms the network. A disadvantage of this method is the limited size of the sample and problems in analyzing the mechanical properties of the network. 

Fittschen C, Hippier H, ViskoIczB (2000) The (1 C-C bond scission in alkoxy radicals thermal unimo-lecular decomposition of f-butoxy radicals. Phys Chem Chem Phys 2 1677-1683 Gajewski E, Dizdaroglu M (1990) Hydroxyl radical induced cross-linking of cytosine and tyrosine in nudeohistone. Biochemistry 29 977-980... 

At 350 - 400°C, thermal degradation rate is considerably increased, and the reaction proceeds with benzene isolation. In 380 - 440°C temperature range, degradation products display cyclosiloxane components of Dn composition, D4<1.5%. Note also that pyrolysis temperature increase induces sharp increase of CFfi, D3 and D4 compounds extracted. Liberation of benzene and methane is due to =Si-C and C-H bond break, which induces cross-linking at the expense of methyl and phenyl groups [47],... 

The radiation synthesis of polymeric nanocomposites is one of the promising technologies in the production of polymeric nanomaterials (Taleb et al. 2012). Along with the polymerization of monomers in situ (Liu et al. 2001, Meszaros and Czvikovszky 2007), radiation-induced cross-linking leads to the reinforcement of the available polymeric matrix owing to additional bond formation both between polymer chains of the matrix (Glhsel et al. 2003, Sharif et al. 2007) and between the polymer matrix and filler particles (KrkljeS et al. 2007, Planes et al. 2010). It is a very useful technique to improve the thermal stability, stress crack resistance, solvent resistance, and... 

Kimaro et al. [93] had prepared free-standing membranes by thermally initiated cross-linking copolymerization of styrene monomers followed by leaching of a polyester present as pore former at a concentration of 1.8 wt% in the reaction mixture. SEM pictures suggested the presence of isolated pores with diameters of up to 1 pm at a low density (< 2 %). In line with permeation data, it could be speculated that trans-membrane channels had been obtained, induced by the presence of a removable macromolecular pore former in the reaction mixture. 

The thermal stability of die polymer after irradiation varies inversely with the radiation dose [129], The yields for crosslinking and scission for several PVDF grades and its copolymers are given in Table 52.17. No substantial differences have been found for the radiation induced cross-linking of the a-, P-, and 7-crystalline forms of PVDF [130]. 

When the monomer shown in Figure 11.17 is heated with a thermal initiator [bis-(4-ferf-butylcyclohexyl) peroxycarbonate] to induce cross-linking, the ionic conductivity of the cross-linked gel polymer electrolyte reaches 6.2 x 10 S/cm at room temperature. Its electrochemical window is greater than... 

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