Squalane stability

More complex with respect to molecular interaction is the case of formation of non-aqueous films on the surface of aqueous solutions from non-ionic surfactants [528], Films from octane were obtained by adsorption from drops of octane/non-adsorbing diluent (squalane) mixture. Occasionally the spreading of alkanes on aqueous surfactant solution gives stable thin oil films (e.g. on solutions of the anionic surfactants Aerosol OT) [529,530], Some evidence about the stability of asymmetric films can be derived from the data about the surface pressure and spreading coefficients of liquids on water surface. These data are known for many organic liquids [531,532], It should be also noted that the techniques for determination of the spreading coefficients have improved considerably [533,534]. Most precise values were obtained by measuring the surface pressure of a monolayer with a special substance introduced as an indicator [533]. 

Gel emulsions were applied successfully for the first time in aldol additions of DHAP to phenylacetaldehyde and benzyloxyacetaldehyde as model aldehydes catalyzed by RAMA [24]. The first interesting observation was that the stability of RAMA in water-in-oil gel emulsions improved by 25-fold compared to that in dimethylformamide/water l/4v/v co-solvent mixture. The reported experimental data concluded that both the highest enzymatic activities and equilibrium yields were observed in water-in-oil gel emulsion systems with the lowest water-oil interfacial tension attained with the most hydrophobic oil component (i.e. tetradecane, hexadecane, and squalane). 

Each of these groups of phases includes the numerous items of various trade names, different average molecular weights, viscosity, thermal stability, and so forth, but all of them are very close to each other by polarity. Up to the middle of the 1970s, the preferred nonpolar phase was squalane (isoprenoid alkane C30H62). This phase is no longer used because of its low thermal stability (only about 110°C). However, this obsolete phase maintains its importance as a nonpolar standard in gas chromatography. Other phases may be characterized by differences of RI values of specially selected test compounds between the phase under consideration and squalane, for example ... 

A comparison between a HAS and a PAO as stabilizers against the oxidation of PP showed that they behave differently [4]. Based on experiment showing the ability of the HAS and the PAO to reduce the oxidation rate of decalin, squalane and decalin/lauryl aldehyde mixtures, it is shown that the HAS is mainly active in the presence of aldehydes. For unstabilized PP it is shown that aldehydes play an important role in its oxidation [5]. These results are used to propose an oxidation mechanism for PP and a mechanism underlying the action of HAS. 

The influence of the stabilizers mentioned in Figure 1 was studied by oxidizing three different model compounds decalin (a cyclic hydrocarbon which, like PP, contains secondary and tertiary carbons), squalane (a high molecular weight aliphatic hydrocarbon which also contains secondary and tertiary carbons), a mixture of 10% lauryl aldehyde in decalin, which could serve as a model for partly oxidized PP. All reactions were initiated with 1% of t-bulylhydroperoxide and performed at 120°C (for details see ref. 4). 

Figure 8. Influence of 0.1 wt % stabilizer on the oxidation rate of squalane at 120°C. Control (+), HAS-1 ( l) and PAO-1 (o). Bars show the standard...

It is clear that the efficiency of the different stabilizers highly depends on the model system. PAOs are effective in all systems, but HAS are not effective in decalin. The oxidation of decalin mainly takes place at the tertiary carbon, leading to cyclodecanone and cyclodecanol [8]. This oxidation does not lead to the formation of aldehydes and acids. When aldehydes are added to decalin HAS becomes effective, so HAS is effective against the oxidation of aldehydes. HAS is also effective against the oxidation of squalane, which, like decalin, is a hydrocarbon containing secondary and tertiary carbons. However, because of its... 

A derivative of squalene called squalane, where all the double bonds are saturated by hydrogenation, has better scope of appHcations than the squalene due to its improved oxidative stability. 

Figure 8.8 The effect of calcium carbonate on the stability of squalane...

Curvature in OIT vs phenol concentration (Figure 3.22) can originate from stabilizer volatile loss [27, 28] in the conditions in which DSC-OIT is performed. As a matter of fact, the slope for squalane -I- A04 is lower than for squalane -I- A02 whereas both stabilizers are expected to display a comparable efficiency in trapping radicals linked of a comparable Bond Dissociation Energy for O-H group. 

FIG. 11 Effect of carbon number of the oil on the stability of alkane ultrafine emulsions at 25°C. Lp, liquid parafin S, squalane. (From Ref. 10.)... 

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