Thermal stability grease

Perfluorination techniques have been developed for the conversion of many hydrocarbons to their perflnorinated counterparts. Flnorocarbons are chemically inert becanse of their kinetically nmeactive carbon skeletons and have been considered as blood substitntes becanse of their high oxygen solnbUity. The thermal stability and low secondary bond forces of flnorocarbons have contributed to their use as greases, lubricants, and vapor-phase heat transfer reagents. 

Polycyclic aromatic hydrocarbons occur as natimal constituents and combustion products of fossil fueb, and are widespread environmental contaminants [9]. These compounds exhibit high chemical and thermal stabilities, and thus have been widely used as insulating liquids for transformers, as grease for vacuum pumps and turbines, and as coolants. Moreover, they have found application in the production of wrapping papers, carbon paper, inks, paints, tyres, and many other products. 

Because of their thermal stability and low viscosity-temperature coefficient, silicone fluids find use as hydraulic fluids, lubricants and greases. Other applications include textile finishes, mould release agents and anti-foaming agents where water repellency, non-stick characteristics and surface activity respectively are utilized. 

The properties of ester oils and complex esters are improved by additives, such as viscosity-index improvers of the methacrylate type. On the other hand, these ester oils are also used as base stock and additive for lithium greases (- lubricating greases). Perfluorinated alcohols (->perfluoro alkyl compounds) are sometimes built in ester oils to increase thermal stability. 

The selection of an appropriate liquid phase for an analysis depends on several factors but principally on the compounds to be separated. Phases which may be suitable for the separation of a small selected group of organic acids may not be suitable when other acids are present. Clearly, non-polar phases separate compounds with respect to boiling point or molecular weight and will only permit elution of compounds which are volatile within the thermal stability range of the phase. Equivalent constraints apply to polar phases. Prior to the introduction of the modified silicone oil liquid phases, the phases most commonly in use were, for non-polar conditions, silicone grease or Apiezone L and for polar columns the polyglycols, polyesters or polyethers. 

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