Thermal oxidation scheme

The polymers prepared by phenylboration polymerization of diynes exhibit relatively high stability against air and thermal oxidation (scheme 30).55... 

Polymer (RH) oxidation, irrespective of the precise initiation process, can be expressed largely in terms of the classical, thermal oxidation scheme (reactions 1-3) (9). In the case of PP, tert.-... 

F. Persson, L. H. Thamdrup, M. B. L. Mikkeisen, S. E. Jaarigard, P. Skafte-Pedersen, H. Bruus, and A. Kristensen, Double thermal oxidation scheme for the fabrication of Si02 nanochannels, Nanotechnology, 18, 245301... 

Concerning the above experimental material (refer to [1 - 5]), Schemes of PI, PAl, PPQ, PEI and PSF thermal oxidation schemes may be shown as follows ... 

Other variations of the dual-bed scheme exist as a combination of thermal oxidizing reactors and catalytic reducing reactors. The Questor company has developed a reactor with three zones the first zone is a thermal reactor with limited air to raise the temperature of the exhaust gas, the second zone is a catalytic bed of metallic screens to reduce NO, and the third zone is another thermal reactor where secondary air is injected to complete the oxidation of CO and hydrocarbons (45). 

A typical synthetic route to the incorporation of pendent carboranyl units into a polymer chain is shown in scheme 3. Poly(o-carboranyl-organo-siloxane)s have been successfully prepared through hydrolysis of dimethyldichlorosilane in the presence of carboranedichloromethylsilane. The polymer has some of the elastomeric characteristics of the parent poly(siloxane) however, the thermal-oxidative cleavage of the o-carboranyl pendent group is reported to occurat lower temperatures than that for the thermooxidative cleavage of Si—O and Si—C bonds.10 Thermal studies have... 

Whatever the initial step of formation of surface silyl radicals, the mechanism for the oxidation of silicon surfaces by O2 is expected to be similar to the proposed Scheme 8.10. This proposal is also in agreement with the various spectroscopic measurements that provided evidence for a peroxyl radical species on the surface of silicon [53] during thermal oxidation (see also references cited in [50]). The reaction being a surface radical chain oxidation, it is obvious that temperature, efficiency of radical initiation, surface precursor and oxygen concentration will play important roles in the acceleration of the surface oxidation and outcome of oxidation. 

The products of thermal oxidation of polyethylene films can be characterized by C FTNMR furthermore, using the spin-lattice relaxation technique, quantitative estimates can be made of the oxidized functional groups. Observation of the development progress of the various functional groups leads to the postulation of hydroperoxides as the primary oxidation products, which undergo further transformations to the other derivatives in a complex scheme . 

General Scheme for Chain Propagation. The reactions which have been discussed may be combined into a system of chain propagation which should be a general one during the thermal oxidation of alkanes. 

Scheme 1 Proposed mechanism for the thermal oxidation of water by Co3+ 9...

An interesting aspect of fused 1,2-thiazetidine A-oxides is their propensity for thermal isomerization. Thus, after heating the 1,2-thiazetidine 54 at 120 °C, the 1,4-thiazine A-oxide 55 was obtained as a pair of isomeric products (ratio 4 3, 78% yield) which differed only in the configuration of the A-oxide (Scheme 4). Irradiation of this 1,2-thiazetidine A-oxidc at A = 300 nm also effected isomerization affording the same ratio of products as that observed in the thermal process <1997SL167>. 

It might be assumed that, as condensed-phase flame retardants function by modifying the normal thermal degradation processes of polymers, they would also function as thermal stabilizers and that thermal antioxidant stabilizers would show flame-retardant properties. However, these statements are rarely the case, and to understand why, it is necessary to compare the mechanistic aspects of flame retardance as discussed earlier with those of thermal degradation and thermal oxidation as well, briefly alluded earlier, and in the case of the latter, the Bolland and Gee mechanism,17 in Scheme 2.1. 

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