Properties of Stearic Acid

Y. Kakiuchi. Proc. Japan Acad. 23, 65-8 (1947) (in English). Crystal structure and electric properties of stearic acid and cetyl alcohol. 

TABLE 10-6. SOME PROPERTIES OF STEARIC ACID MONOLAYERS ADSORBED ON METALS... 

Aging and tear strength properties of stearic acid/ZnO compounds are superior to those of oleic acid systems. 

The focus of this chapter is on the chemosensory properties of stearic acid in the human oral cavity. Stearic acid is an eighteen-carbon, saturated fatty acid. As with other long-chain fatty acids, stearic acid is thought to be detected by multiple sensory systems in the human oral cavity [4, 7, 8, 11, 20,22]. 

A major roadblock in identifying gustatory properties of stearic acid is the absence of a delivery system that can present high concentrations or amoimts of hydrophobic stimuli in the absence of tactile (and olfactory) cues. For example, Chale-Rush et al. [4, 22] and Mattes [2] foimd that the detection of smell and taste thresholds of fatty acid stimuli differed with presentation conditions. This absence of a suitable delivery system ciurently limits suprathreshold studies on fatty acid chemosensation in the oral cavity. 

With the development of biomedicine and biomaterial, more and more properties of stearic acids will be found and applied in biomedicine for improving the living and health conditions of human beings. 

In a series of organic acids of similar type, not much tendency exists for one acid to be more reactive than another. For example, in the replacement of stearic acid in methyl stearate by acetic acid, the equilibrium constant is 1.0. However, acidolysis in formic acid is usually much faster than in acetic acid, due to higher acidity and better ionizing properties of the former (115). Branched-chain acids, and some aromatic acids, especially stericaHy hindered acids such as ortho-substituted benzoic acids, would be expected to be less active in replacing other acids. Mixtures of esters are obtained when acidolysis is carried out without forcing the replacement to completion by removing one of the products. The acidolysis equilibrium and mechanism are discussed in detail in Reference 115. 

A comparison test carried out over a commercial Ni catalyst showed that early formation of stearic acid (C18 0) results in a very high pour point, thus indicating that very high selectivity is required to improve oxidative stability while retaining cold properties. 

The amount of bonded surfactant can be determined by simple techniques. A dissolution technique proved to be very convenient for the optimization of non-reactive surface treatment and also for the characterization of the efficiency of the treating technology [74,84]. First the surface of the filler is covered with increasing amounts of surfactant, then the non-bonded part is dissolved with a solvent. The technique is demonstrated in Fig. 11, which presents a dissolution curve of stearic acid on a CaC03 filler. Surface treatment is preferably carried out with the proportionally bonded surfactant (cioo)j this composition the total amount of surfactant used for the treatment is bonded to the filler surface. The filler can adsorb more surfactant (Cjnax)>but during compounding a part of it can be removed from the surface by dissolution or simply by shear and might deteriorate properties. 

This work aims to produce mixed calcium carboxylate stabilisers for use in place of calcium stearate for the stabilisation of PVC. The new stabilisers are based on mixed salts of stearic acid with derivatives of phthalic or maleic acid and also with branched alpha, alpha-branched carboxylic (C12-C16) acids, noted for their lower cost and adequate effectiveness. Test results are examined in detail for the performance of these stabilisers in terms of service properties, processability, and stabilising action. 2 refs. (Translated from Plasticheskie Massy, No.5, 2000, p.19)... 

The construction and properties of monolayers has been well documented by Kuhn (1979) and the photochemical reactions which occur in such systems reviewed (Whitten et al., 1977). Molecules in monolayers are usually ordered and in the case of rru/i -azastilbenes irradiation of the ordered array produces excimer emission and dimers (Whitten, 1979 Quina et al, 1976 Quina and Whitten, 1977). This contrasts with what is found when the fra/jj-isomers of such compounds are incorporated into micelles. In such systems the predominant reaction is cis-trans isomerisation excimer emission is lacking. It is suggested that the lack of isomerisation in the fatty acid monolayers is due to the tight packing and consequent high viscosity of such systems. Styrene also dimerises in a fatty acid monolayer. Interestingly, the products formed on photo-oxidation of protoporphyrins are dependent upon whether the reaction is carried out in a monolayer or a micelle (Whitten et al., 1978). Zinc octa-ethylporphyrin exhibits excimer emission in monolayers (Zachariasse and Whitten, 1973). Porphyrins are photoreduced by amines in monolayers (Mercer-Smith and Whitten, 1979). Electron-transfer reactions have been carried out with monolayers of stearic acid containing chlorophyll and electron acceptors such as quinones (Janzen et al., 1979 Janzen and Bolton, 1979). 

The properties of fatty acids and of lipids derived from them are markedly dependent on chain length and degree of saturation. Unsaturated fatty acids have lower melting points than saturated fatty acids of the same length. For example, the melting point of stearic acid is 69.6°C, whereas that of oleic acid (which contains one cis double bond) is 13.4°C. 

A wide range of different grades of stearic acid are commercially available that have varying chemical compositions and hence different physical and chemical properties see Table III. A specification for stearic acid is contained in the Food Chemicals Codex (FCC). 

Other properties of fatty acid monolayers such as the phase transition temperature are consistent with the field strength theory stearic acid monolayers formed rigid films on alkaline earth subphases (17, 35). The temperature of the phase transition from rigid to fluid monolayers, estimated by the Devaux talc test, was a function of pH and buffer composition (Figure 17). Thus transition temperature at pH 6 decreased in a weak field sequence (I in Table III) while transition temperatures at pH 8 decreased in an intermediate field sequence (III or IV in Table III). Since variables such as tt are not controlled in these experiments, it is surprising that transition temperature data followed these sequences. 

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