Structure aliphatic

In the narrow sense, bis-maleimide resin means the thermosetting resin eom-posed of the bis-maleimide of methylene dianiline (BMI, bis(4-maleimidophenyl)-methane) and methylene dianiline (MDA, bis(4-aminophenyl)methane) (Fig. 1). Beeause of the addition meehanism, the resin is eured without elimination, whieh is a eharacteristic of this resin. Bis-maleimide resin is used as a thermally stable matrix up to 204°C (400 F) whieh typical epoxy resins may not normally be used. However, in spite of having an imide structure, bis-maleimides are classified as being moderately thermally stable resins. The aliphatic structure of the resin is not stable for long periods above 232°C (450°F.) If a highly aromatic thermally stable thermosetting resin is necessary, acetylene end-capped aromatic imide-based oligomers should be used. 

Alicyclic Hydrocarbons. These refer to cyclic analogues of aliphatic hydrocarbons and are named accordingly, using the piefix cyclo-." Their properties are similar to their open-chain aliphatic counterparts. Alicyclic hydrocarbons are subdivided into monocyclic (cycloalkanes, cycloalkenes, cycloalkynes, cycloalkadienes, etc.) and polycyclic aliphatic compounds. Monocyclic aliphatic structures having more than 30 carbon atoms in the ring are known, but those containing 5 or 6 carbon atoms are more commonly found in nature [47, p. 28]. 

The PET polymer structure can also be generated from the reaction of ethylene glycol and dimethyl terephthalate, with methyl alcohol as the byproduct. A few producers still use this route. The aromatic rings coupled with short aliphatic chains are responsible for a relatively stiff polymer molecule, as compared with more aliphatic structures such as polyolefin or polyamide. The lack of segment mobility in the polymer chains results in relatively high thermal stability, as will be discussed later. 

In contrast, there are less experimental data available for aliphatic structures, much more present in natural compounds. Fluoiination lowers lipophilicity and enhances the hydrophobicity. However, other factors, like strong hydrogen bonds... 

Table IX shows the effect of two chemically very different organic liquids on the glass temperature of polystyrene (2). Ethylbenzene, with a chemical structure very similar to that of the polystyrene monomer unit, greatly lowers Tg and therefore, is a much more efficient plasticizer for polystyrene than paraffin oil, with its completely aliphatic structure.

Growth of the 1700 cm.-1 band is accompanied by reduction in the intensity of all absorptions associated with nonaromatic C-H groups. Currently held views are that aliphatic structures are destroyed during the oxidation of coal, and the changes in absorption pattern support this. 

Aliphatic structures are still of major importance in the second group of resinites, those of the bituminous coals, but aromatic structures are present in significant amounts. The spectra of these resinites display the type of absorption pattern that has come to be associated with other coal macerals, particularly the sporinites and to a large extent the vitrinites. This pattern is established in the resinites of the high volatile bituminous coals. Furthermore, resinites of this group are reactive during carbonization and oxidation processes in which their behavior parallels that of similarly affected vitrinites of equivalent rank. 

Dr. Heredy The facts are as stated, but I agree that there may be a little difficulty in accounting for them. However, surely hydrogen transfer reactions, perhaps via the solvent, could place hydrogen from aliphatic structures on free radicals centers created by C-C bond scission on aromatic nuclei. 

A decade of work on the distribution of carbon (and also hydrogen) has now led to a fair assessment of the aromatic and hydroaromatic contents of coals although there may still be differences of opinion about the accuracy of these values (16). Our information on the aliphatic structures present in coal is, however, less complete. 

It is evident, therefore, that the aromatic carbon alone yields coke, and hydroaromatic carbon yields tar. Since neither appears to contribute substantially to the formation of gases (during the low temperature pyrolysis), it seems certain that the gases of low temperature pyrolysis owe their origin largely to the aliphatic structure in coal. At least it is now certain that methane formation is quite independent of the aromatic and hydroaromatic structures in coal. 

MAZIHADAft ET 41. Aliphatic Structure in Coal and Hydrogen undor Atmospheric Pressure... 

MAZUMDAR FT Al. Aliphatic Structures in Coal (Assussud From Pyrolysis) with Othor Forms of Carbon in Coal... 

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