Degradation and Decomposition

Several methodologies can be used to identify not only crude or refined product type, but also the brand, grade, and, in some instances, the source crude. The petroleum industry has yielded conventional methods for the characterization of refined products. The simplest is the routine determination of API gravity and development of distillation curves where NAPL is present. More sophisticated methods include gas chromatography and statistical comparisons of the distribution of paraffinic or n-alkane compounds between certain C-ranges. With increased degradation and decomposition, the straight-chain hydrocarbons ( -alkanes) become less... 

Because of the complex nature of most biological samples, a single fractionation technique may not be adequate for the separation of the wide range of molecules present. Better resolution of some molecules is obtainal when properties other than differences in size are exploited. These include differences in ionic characteristics, affinity for other molecules and hydrophobicity. In separations that involve any one or more of these properties, the sample constituents interact with the column material and are then eluted with a suitable eluant. As a consequence of this interaction, and the use of eluants, whose properties may not closely resemble those of the medium found in vivo, the metal may dissociate from the ligand. In addition, as the complexity of the sample increases it is difficult to predict the behaviour of the various constituents. Undesirable effects leading to irreversible interaction between some molecules in the sample and the column packing material, degradation and decomposition of some constituents may result. Furthermore, it may be difficult to rid the column of certain trace metal contamination. 

Liquid inventory. With unstable chemicals, minimizing liquid inventories at hot temperatures minimizes product loss due to degradation and decomposition reactions. In batch distillation, excessive liquid inventory lowers product recovery. With hazardous chemicals, minimizing liquid inventories lowers the hazard. 

Van Krevelen DW, "Group Contribution Techniques for Correlating Polymer Properties and Chemical Structure", in Bicerano J (Ed) "Computational Modelling of Polymers", Marcel Dekker, New York, 1992, Chap. 1. Vasile C, "Degradation and Decomposition", in Vasile C (Ed), "Handbook of Polyolefins", Marcel Dekker, New York, 2nd Ed, 2000, Chap. 17. 

Vasile C, "Degradation and Decomposition", in Vasile C (Ed), "Handbook of Polyolefins , Marcel Dekker, New York, 2nd Ed, 2000, Chap. 11. 

Supercritical fluids are effective at much lower temperatures than distillation, and their application in separation avoids degradation and decomposition of heat-labile compounds. Attractiveness of supercritical extraction processes are due to the sensitivity of responses to process variables, promise of complete and versatile regeneration of solvents, energy savings, enhanced solute volatilities, solvent selectivities, favorable transport properties for solvents, and state governed effectiveness of solvents which enables the use of low cost, non-toxic, environmentally acceptable solvents. The impact of inherent characteristics of supercritical fluids on separations is summarized in Table 21.1.5. 

Degradation and decomposition. The evolving products are combustible gases and vapours, liquids, entrained solid particles as smoke, and solid carbonaceous residue. Thermal decomposition is affected by the decomposition temperature, by the endothermic or exothermic character of the decomposition, and by the decomposition mechanism of the polymer. 

Alvarez V, Rodriguez E, Vazquez A (2006) Ther mal degradation and decomposition of jute/ vinylester composites. J Therm Anal Calorim 85 383-389... 

Polyolefin degradation and decomposition constitutes the topic of an enormous number of publications, so that it is practically impossible to cite them all. Most of... 

Both degradation and decomposition are mainly dependent on structural defects, with photodegradation also strongly dependent on nonbonded chemical impurities. 

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