Slow Thermal Decomposition

The peioxide and a2o thermal initiatois also aie photochemicady unstable and have been used as ladical sources at weU below thek nornial theimal decomposition tempeiatuies. Howevei, thek industiial use as photoinitiatois has been limited because thek light-absoiption chaiacteiistics fiequentiy aie unsuitable and because of the obvious potential complication owing to thek slow thermal decomposition, which leads to pool shelf-life and noniepioducible photoactivity in given formulations (88). Further information on photoinitiatois can be found in the Hteiatuie (92). 

Slow thermal decomposition of the alkali metal salts of 3 takes place quantitatively in accordance with Eq. (5), where M represents an... 

Organic hydroperoxides, such as -butyl hydroperoxide, (0113)30—0-OH, likewise induce polymerization in vinyl monomers through the action of free radicals formed as primary intermediates in their decomposition. The following compounds, or classes of compounds, also are effective polymerization initiators at temperatures where they undergo slow thermal decomposition by mechanisms which are believed to involve the release of free radicals as indicated ... 

The slow thermal decomposition of gaseous azomethane becomes explosive above... 

It is somewhat endothermic (AH°f (g) +87.5 kJ/mol, 1.0 kJ/g), the liquid may explode on pouring or sparking at 2°C, and the gas readily explodes on rapid heating or sparking [1,2], on adiabatic compression in a U-tube, or often towards the end of slow thermal decomposition. Kinetic data are summarised [3], The spontaneously explosive decomposition of the gas was studied at 42-86°C, and induction periods up to several hours were noted [4], Preparative precautions have been detailed [5],... 

The slow, thermal decomposition of hydrazoic acid in a static system has been studied by Meyer and Schumacher58. It turned out to be completely governed by heterogeneous catalysis. There are no studies on the kinetics of the homogeneous decomposition of this substance save for the investigation of its decomposition flame59. From the variation of flame properties with pressure it can be deduced that second-order reactions control the over-all rate. The unimolecular reaction... 

Morris et al. (1991) obtained hematite of very small particle size ( 10 nm), termed nanophase by slow thermal decomposition in air of tri-Ee -acetato-hy-droxy-nitrate. XRD shows only two broad lines as in a 2-line ferrihydrite, but the magnetic hyperfine field at 4.2 K of 50.4 T appears to be more in agreement with poorly crystalline hematite. Well-crystalline hematite and Al-hematite were produced by decomposing Ee-Al-oxinates at 700 °C (da Costa et al. 2001). 

The researches of Wischin [113] and those of Garner and Maggs [84] have shown that metallic nuclei are formed during the slow thermal decomposition of silver azide. These researches were carried out by means of an optical microscope. 

Pentaalkylstiboranes are pale yellow liquids that can be distilled under reduced pressure (Table IV). Although distillation at atmospheric pressure is also possible, it is to be avoided. A violent explosion was reported in one case when a larger quantity of (CH3)6Sb was rectified (still temperature 160°C) (33). When small amounts of IRSb compounds are heated, slow thermal decomposition is observed, which leads to trialkylantimony compounds, alkane and alkene (86a) ... 

The unique phosphine-carbon dioxide complex Cp2Ti (C02)PMe3 is prepared by treatment of Cp2Ti(PMc3)2 with dry CO2 at -180°C (equation 50). Slow thermal decomposition of Cp2Ti(C02)PMc3 at room temperature leads principally to Cp2Ti(CO)2. ... 

Slow thermal decomposition was examined by Garner [Vol. Ill, p. 171). It was shown 1112 that when silver azide is heated, silver is formed in an oriented way througli the a/idc lattice. The rapid growth of nuclei by the surface migra- tion of metal in lead azide seems to be demonstrated 113]. Oioi and Boutin [1141 showed the existence of azide radicals in the course of the decomposition. 

Thermal decomposition of polyester copolymers is of considerable interest because of their common use in practice. A number of reports are available in literature describing either pyrolysis or slow thermal decomposition of polyester copolymers [57-60], etc. Some of these reports are summarized in Table 10.1.10. 

The factors governing the slow thermal decompositions of inorganic azides have been discussed by Fox and Hutchinson [18]. They draw attention to the interest shown in early studies for fitting of kinetic results to rate equations based on nucleation and growth models. Support of kinetic interpretations by microscopic observations (e g., [21]), contributed significantly towards establishment of the role of the active, advancing interface in solid state reactions. The kinetic characteristics of some of the metal azides are summarized in Table 11.1. 

Studies of slow thermal decomposition, when combined with the hot-spot theory, proved to have particularly interesting consequences for understanding the sensitivity of the azides and their troublesome and seemingly temperamental response to some stimuli. 

Figure 1. Energy-level diagram used in the interpretation of the mechanism of slow thermal decomposition. An electron from an azide ion in the metal azide is promoted directly from the valance to the conduction band, transferred via the intermediate exciton levels introduced by impurities or defects, or promoted to the conduction band of the metal formed by decomposition, i// is the electron affinity of the solid azide compound and 0 the work function of the metal.

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