Product oils molecular weight determinations

The products, which were obtained as viscous, pale amber oils, were purified by vacuum distillation or molecular distillation, whichever was best suited to the particular product. The yield of dialkylated p-cresol was 85-95%. Freedom from appreciable amounts of monoalkylated product was established by vapor phase chromatography (VPC), thin-layer chromatography (TLC), and molecular weight determination. The products obtained from propylene trimer and tetramer had no appreciable antioxidant activity) and will not be considered further here. 

Table V. Molecular Weight Determinations for Bitumen and Product Oils...

The reaction mixture, condensed in the traps as a slurry, is first washed with potassium hydroxide solution to remove acidic components. The product is then fractionated to separate the greater part of the NgO. At this stage, the NFg becomes a colorless liquid covered with a white layer of solid NgO. In order to remove this, the NFg must be repeatedly and very carefully fractionated. The last traces of NgO may be more conveniently separated by filtering the NFg at —196°C on a low-temperature filter. It is completely pure after only one filtration. Finally, the air dissolved in the NFg is removed, using an oil pump vacuum for several hours, while the trap with the product is immersed in liquid nitrogen. Purity is best ascertained by molecular weight determination (vapor density measurement). 

In many products, the spin-relaxation properties of the components can be different due to molecular sizes, local viscosity and interaction with other molecules. Macromolecules often exhibit rapid FID decay and short T2 relaxation time due to its large molecular weight and reduced rotational dynamics [18]. Mobile water protons, on the other hand, are often found to have long relaxation times due to their small molecular weight and rapid diffusion. As a result, relaxation properties, such as T2, have been used extensively to quantify water/moisture content, fat contents, etc. [20]. For example, oil content in seeds is determined via the spin-echo technique as described according to international standards [64]. 

Detailed analysis of residual products, such as residual fuel oil, is more complex than the analysis of lower-molecular-weight liquid products. As with other products, there are a variety of physical property measurements that are required to determine that residnal fnel oil meets specifications. But the range of molecular types present in petrolenm prodncts increases significantly with an increase in the molecular weight (i.e., an increase in the number of carbon atoms per molecule). Therefore, characterization measurements or studies cannot, and do not, focus on the identification of specific molecular structures. The focus tends to be on molecular classes (paraffins, naphthenes, aromatics, polycyclic compounds, and polar compounds). 

Much work has been done on the incorporation of castor oil into polyurethane formulations, including flexible foams [64], rigid foams [65], and elastomers [66]. Castor oil derivatives have also been investigated, by the isolation of methyl ricinoleate from castor oil, in a fashion similar to that used for the preparation of biodiesel. The methyl ricinoleate is then transesterified to a synthetic triol, and the chain simultaneously extended by homo-polymerization to provide polyols of 1,000, 000 molecular weight. Polyurethane elastomers were then prepared by reaction with MDl. It was determined that lower hardness and tensile/elongation properties could be related to the formation of cyclization products that are common to polyester polyols, or could be due to monomer dehydration, which is a known side reaction of ricinoleic acid [67]. Both side reactions limit the growth of polyol molecular weight. 

While the analysis of the composition products from the thermal and oxidative treatment of fats and oils has been widely studied, systematic studies concerning separation, determination, and elucidation of the chemical structure of the higher-molecular-weight materials such as dimers and... 

Oil Content. The production of petroleum waxes involves the removal of oil therefore, the oil content (actually the percentage of oil and low molecular weight fractions) is one indication of the quality of the wax. Oil content is determined (ASTM D721) as that percentage of the wax soluble in methyl ethyl ketone at —31.7 °C. 

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