Volatile products from thermal

Study of Volatile Products from Thermal Analyzers. The MC-2 mass chromatograph is ideally suited for thermal analysis or pyrolysis studies for the obvious reasons of quantitative and qualitative analysis and also for its unique trapping assembly. With the traps, sample effluents can be collected and concentrated over extended periods of time prior to analysis. 

G.J. Hartmann et al. (1 4 ) and G.A. Reineccius and R. Liardon (J 5J have recently studied the volatile products from thermally degraded thiamin. A number of different decomposition components were identified including... 

The volatile products from thermal degradation of poly(2-methyl-l,4-phenylene oxide), poly(2,5-dimethyl-l,4-phenylene oxide), and poly(l,4-phenylene oxide)have been analysed by gas chromatography-mass spectrometry. The methyl substituted... 

Tabfe 6.3 Volatile products from thermal decomposition of PEEK identified at different temperatures. 

The vapour pressures of the main volatile compounds involved in esterification and polycondensation are summarized in Figure 2.25. Besides EG and water, these are the etherification products DEG and dioxane, together with acetaldehyde as the main volatile product of thermal PET degradation. Acetaldehyde, water and dioxane all possess a high vapour pressure and diffuse rapidly, and so will evaporate quickly under reaction conditions. EG and DEG have lower vapour pressures but will still evaporate from the reaction mixture easily. 

This experiment showed that some volatile component was formed in the thermal decomposition of tetramethyllead and that this compound consumed a cold lead mirror with formation of a volatile product. If, instead, a zinc mirror was first deposited and allowed to be consumed by the volatile product from decomposition of tetramethyllead, dimethylzinc could be identified as the product. Paneth concluded that free methyl radical was formed in the thermal reaction and could determine its half-life to be 0.006 seconds under the reaction conditions employed. Also, free ethyl radicals could be formed in... 

Aikawa K, Chikuni K. 1988. Antimutagenic effect of volatile decomposition products from thermally oxidized linoleate. Mutat Res 208 163-166. 

Hydrogen abstraction by the C from the or Q2 may also lead to the formation of these products. All of the aliphatic hydrocarbons formed according to eqs. (19) through (32) have been reported l to be the volatile products of thermal degradation of polyethylene. 

All of tl products l,3 triphenylbenzene, 1,3-diphenylpropane, 1,3,5-triphenylpen-tane, ethylbenzMie, methylben2 ne, and styrene are volatile products of thermal degradation of polystyrene This kind of intramolecular cyclization is not likely to be important in thermal degradation of poly(methyl methacrylate) and poly(a-methylstyrene), because the reactive site is linked to two bulky substituents which restrict the rotation of the terminal carbon atom containing the unpaired electron and thus prevent it from coming into proper orientation to attack the other carbon atoms in the chain. 

Mass spectra of volatile products from photothermal and thermal degradations at 354°C and of photothermal degradation at 200 and 250 C are illustrated in figure 1. They are all typical of a mixture of hydrocarbons with the main peaks separated by 14 units (CH2). They are generally similar, except that as the degradation temperature is decreased, the lines at mass numbers 15 and 16 become relatively much more intense. These two lines, as well as forming part of the breakdown pattern of higher hydrocarbons, are characteristic of methane. Thus it may be concluded that the relative proportions of methane in the volatile products... 

By comparison with mineral oils, the viscosity of silicone oils changes little with temperature. They are thermally stable, low volatility products (from ca. 50 mPa s) exhibiting long term stability at 150°C in air and even up... 

Figure 1. Mass spectra of volatile products from photothermal and thermal degradations of PP. A, thermal at 354°C B, photothermal at 354°C C, photothermal at 200°C D, photothermal at 250°C.

Pyrolysis with in situ methylation in the presence of TMAH is now commonly applied for the structural investigation of HS. It has been reported, however, that TMAH not only methylates polar pyrolysate but also assists in bond cleavage. For example, TMAH was found as effective at 300°C as at 700°C for the production of some volatile products from HS, indicating that pyrolysis occurs with equal effectiveness at subpyrolysis temperature of 300°C. It is believed that TMAH pyrolysis is actually a thermally assisted chemolysis rather than pure pyrolysis and it can cause hydrolytic ester and ether bond cleavage even at lower temperature, resulting in some unwanted side reactions, e.g., artificial formation of carboxylic groups from aldehydes. Therefore, TMAH thermochemolysis at low temperature, e.g., 300°C has been proposed. This technique offers several advantages over classical flash pyrolysis or preparative pyrolysis apparatus " ... 

Table I. Various Aromatic Molecular Types Identified as Constituents of the Volatile Products from the Thermal Decomposition of Asphaltene Fractions...

A substantial amount of work has been published on the reactions of [Ru3(CO)i2] particularly with P donor ligands and this is very thoroughly reviewed in references 1 and 3-5. The usual products from thermal reaction of [Ru3(CO),2] with PRj are [Ru3(CO) PR3)3], the mono- and di-substituted derivatives normally not being isolated unless bulky phosphines such as PCy3 are used. With phosphines with small substituents e.g. PHj, PMc3 it is also possible to isolate [Ru3(C-0)g(PR3)4]. Likewise reaction of [Ru3(CO),2] with PFj/CO mixtures gives in addition to [Ru(C-0)j (PF3) ] (Section 45.5.1.3) a less volatile residue of red crystals identified by mass spectrometry as a mixture of [Ru3(CO),2 (Pp3) ] (n Similar results are obtained with AsR, although... 

Chemical transformations of the volatile products from the initial coal destraction in the high-temperature conditions of thermal plasma ... 

Overall, taking into account the theoretical considerations stated above and available laboratory data, acetaldehyde remains the major volatile product from PET during thermal degradation/oxidation. Of the proposed products mentioned above, we cannot be certain which one is important few have been identified in studies to date. Many of the initially derived small-molecule species may undergo further reaction, or reaction with other species in or on the polymer. 

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