Pyrolysis definition

The extent of short-chain branching in PE may be quantitatively determined by a variety of techniques including IR. 1 pyrolysis Ct., 7" and y-radiolysis."84 The most definitive information comes from l3C NMR studies.2S5"2 0 The typical... 

Conventional rubber compound analysis requires several instrumental techniques, in addition to considerable pretreatment of the sample to isolate classes of components, before these selected tests can be definitive. Table 2.5 lists some general analytical tools. Spectroscopic methods such as FTIR and NMR often encounter difficulties in the analysis of vulcanised rubbers since they are insoluble and usually contain many kinds of additives such as a curing agent, plasticisers, stabilisers and fillers. Pyrolysis is advantageous for the practical analysis of insoluble polymeric materials. 

EXMAT - A Linked Network of Expert Systems for Materials Analysis. Seven individual expert systems comprise EXMAT (1) problem definition and analytical strategy (2) instrumental configuration and conditions (3) data generation (4) chemometric/search algorithms (5) results (6) interpretation (7) analytical goals. Dynamic headspace (DHS)/GC and pyrolysis GC (PGC)/concentrators... 

The fuel oils coming out of olefin plants are also characterized by an abundance of polynuclear aromatic molecules, (Same definition as for Figure 2—1). They are sometimes inaccurately referred to as having a high aromatics content. Nomenclature aside, because of this, the burning characteristics of pyrolysis gas oil and pyrolysis pitch are poor. They are smoky, sooty, and gum formers they rend to be more viscous, and because of their polynuclear aromatic concent, they are suspected carcinogens. They are basically a witchs brew of unsavory hydrocarbons.. ... 

Didehydropyridine (97) is less well investigated, and the existence of this intermediate is not yet established definitively. Aryne 97 has been postulated as an intermediate in the gas-phase pyrolysis of 2,3-pyridinedicarboxylic anhydride (107) at 600 °C, which hnally yields (3-ethinyl acrylonitrile (108). Indirect evidence stems from trapping experiments with benzene and thiophene. Photolysis of matrix isolated 107 does not produce 97 (Scheme 16.25). Nam and Leroi ... 

Thermal Inactivation. Heating the wood surface to temperatures above 150 to 200°C definitely has been shown to cause poor adhesion with phenolic adhesives and, possibly, urea adhesives. Early research (60) verified that overheated wood was less wettable and tended to absorb less water from the adhesive. Whether this is caused by extractives, pyrolysis, oxidation of hydroxyl groups, or other chemical reactions at the wood surface has been the subject of much debate. Further, the mechanisms of thermal or "surface" inactivation may vary from species to species. 

The reaction of BPA in supercritical methanol at 340°C and pr = 0.5 is summarized in Figure 3 and led to N-methylaniline as a major product. Benzaldehyde and benzyl alcohol were observed in yields less than 0.1. The yield of toluene was 0.56, roughly equivalent to that observed from neat pyrolysis, whereas the aniline yield was approximately 0.1, substantially reduced from that observed in the neat case. The yield of N-methylaniline surpassed that of aniline, as a value of 0.4 was attained after 120 min. Reaction in 13C-labeled methanol showed the label to reside on the methyl group in the N-methylani1ine product, definitively indicating that methanol reacted with BPA. 

Tetrachlorophthalic anhydride gave a relatively low yield of products derived from tetrachlorobenzyne. The pyrolysis tube was badly carbonized evidently extensive decomposition of the anhydride, the aryne, or the chlorinated products had occurred. Tetrabromophthalic anhydride gave a still lower yield of products. These are not listed in the table because none of them retained all four bromine atoms and could be definitely ascribed to reactions of tetrabromobenzyne, although tri-bromo- and dibromonaphthalene were present in appreciable amounts. Tetraphenylphthalic anhydride also gave low yields of products of the reaction of tetraphenylbenzyne with pyridine. This was not because of the stability of the anhydride and its reluctance to form the aryne, but rather because the aryne preferred to stabilize itself intramolecularly. The behavior of tetraphenylphthalic anhydride is discussed in another Section. 

This study on the kinetic chlorine isotope effect in ethyl chloride50 was extended to secondary and tertiary alkyl halides pyrolyses51. The isotope effects on isopropyl chloride and terf-butyl chloride pyrolysis were found to be primary and exhibited a definite dependence on temperature. They increased with increasing methyl substitution on the central carbon atom. The pyrolysis results and model calculations implied that all alkyl chlorides involve the same type of activated complex. The C—Cl bond is not completely broken in the activated complex, yet the chlorine participation involves a combination of bending and stretching modes. 

For solvolysis of 2-ary 1-2-chloropropanes, r is 1.0 by definition, and this value appears to be approximately correct for pyrolysis of 1-arylethyl acetates. Although the magnitude of the charge is smaller in the latter reaction, resonance stabilization of this charge by the aromatic is proportionally greater because of the absence of the solvent (63T937). Nevertheless, for some very polarizable heterocycles, differences in reactivity be-... 

Assuming the above statements are correct, any two p-xylylene species should be capable of copolymerization in any desired ratio. This is somewhat of a simplification since it has been observed that for each substituted p-xylylene there is a definite ceiling condensation temperature above which it will not condense and polymerize at any appreciable rate. Thus, if the monomer does not condense, it is not available for copolymerization. This was demonstrated in the studies described earlier of the pyrolysis of acetyl-di-p-xylylene and separation of the monomers VI and VII on the basis of widely differing Tc s. 

The present authors found another pyrolysis mechanism leading to optical anisotropy (10), in which no definite liquid phase was observable during the carbonization. In some carbonaceous substances, such as semi-anthracite coal, optical anisotropy over broad regions develops promptly at certain temperatures from the highly viscous stage. The component layers appear to be stacked, and are rearranged by heat-treatment to show optical anisotropy. Such a mechanism can be called the "preordered layer-transformation mechanism". 

---