Of stearic acid

The limiting compression (or maximum v value) is, theoretically, the one that places the film in equilibrium with the bulk material. Compression beyond this point should force film material into patches of bulk solid or liquid, but in practice one may sometimes compress past this point. Thus in the case of stearic acid, with slow compression collapse occurred at about 15 dyn/cm [81] that is, film material began to go over to a three-dimensional state. With faster rates of compression, the v-a isotherm could be followed up to 50 dyn/cm, or well into a metastable region. The mechanism of collapse may involve folding of the film into a bilayer (note Fig. IV-18). 

The adsorption of stearic acid from n-hexane solution on a sample of steel powder is measured with the following results ... 

MI] Tredgold R H and Winter C S 1981 Tunneling currents in Langmuir-Blodgett monolayers of stearic acid J. Phys. D Appl Phys. 14 LI 85-8... 

A study of the effect of stearic acid and 2iac oxide on a sulfonamide-accelerated, sulfiir-cured natural mbber compound dramatically showed the need for both 2iac and fatty acid activators (Fig. 7) (21). 

Panning and pressing is no longer used because of high labor costs, but it gave us the terms single-pressed, double-pressed, and triple-pressed stearic acid. These terms are widely used to denote the quaUty of stearic acid. These commercial "stearic" acids are actually mixtures of palmitic acid and stearic acid. 

Individual particle surfaces can be lubricated by an adsorbed film that produces a smoother surface and/or decreases interparticle attraction. A plasticized binder may serve this purpose. Forming surfaces can be lubricated by coating with a film of low viscosity Hquid such as water or oil. Die surfaces can also be coated with a solution of stearic acid dissolved in a volatile Hquid that rapidly evaporates to leave a lubricating film. 

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. 

Somewhat better results have been obtained with octoates and benzoates but these still lead to some plate-out. The use of liquid cadmium-barium phenates has today largely resolved the problem of plate-out whilst the addition of a trace of a zinc salt helps to improve the colour. Greater clarity may often be obtained by the addition of a trace of stearic acid or stearyl alcohol. Thus a modem so-called cadmium-barium stabilising system may contain a large number of components. A typical packaged stabiliser could have the following composition ... 

The most commonly used stabilizers are barium, cadmium, zinc, calcium and cobalt salts of stearic acid phosphorous acid esters epoxy compounds and phenol derivatives. Using stabilizers can improve the heat and UV light resistance of the polymer blends, but these are only two aspects. The processing temperature, time, and the blending equipment also have effects on the stability of the products. The same raw materials and compositions with different blending methods resulted in products with different heat stabilities. Therefore, a thorough search for the optimal processing conditions must be done in conjunction with a search for the best composition to get the best results. 

This chapter reports the results of studies on the physical, dynamic mechanical, and rheological behavior of zinc oxide neutralized m-EPDM, particularly in the presence of stearic acid and zinc stearate, with special reference to the effects of precipitated silica filler. 

Zinc salt of maleated EPDM rubber in the presence of stearic acid and zinc stearate behaves as a thermoplastic elastomer, which can be reinforced by the incorporation of precipitated silica filler. It is believed that besides the dispersive type of forces operative in the interaction between the backbone chains and the filler particles, the ionic domains in the polymer interact strongly with the polar sites on the filler surface through formation of hydrogen bonded structures. 

Fats can be either optically active or optically inactive, depending on their structure. Draw the structure of an optically active fat that yields 2 equivalents of stearic acid and 1 equivalent of oleic acid on hydrolysis. Draw the structure of an optically inactive fat that yields the same products. 

When 13.66 g of lactic acid, C3H603j is mixed with 115 g of stearic acid, the mixture freezes at 62.7°C. The freezing point of pure stearic acid is 69.4°C. What is the freezing point constant of stearic acid ... 

Using the Molecules Database on the Web site for this book, examine the structure of tristearin, formed by ilk the condensation of three molecules of stearic acid,... 

Heterogeneous catalytic deoxygenation of stearic acid for production of biodiesel. Ind. Eng. Chem. Res., 45, 5708-5715. 

C, 0.25 nm molecule in the coexistence region between the liquid-expanded and the liquid-condensed (L2) phases (b) BAM image of stearic acid at 22°C, 0.60 nm molecule in the coexistence region between the gas (G) and the hquid-condensed (L2) phases. In each of these images, the polarizer angle has been set to 60°. The subphase is milh-Q water acidified to pH 1.8 with HCl. The scale bar in the lower left of each image is 450 p,m. 

FIG. 1 Variation of pressure vs. area isotherm of stearic acid. 

Carboxypolymethylene exhibits a stabilizing effect against separation and viscosity change of a cetyl alcohol-stearic acid-sodium lauryl sulfate system. Samples 1 and 2 are identical, except that the former contains carboxypolymethylene (adjusted to pH 7). Sample 1 shows no separation, while sample 2 shows 13% separation after 6 months. Figure 8 shows the viscosity characteristics of the above samples. The broken line represents the viscosities of sample 1 at different time intervals, and the unbroken line, the viscosities at the same time intervals for sample 2. Apparently the carboxypolymethylene prevents the agglomeration and precipitation of stearic acid, which would result in separation and loss of viscosity. 

As anticipated, SA conversion increases with increasing residence time (1/LHSV) and with increasing temperature to a maximum of about 98%. This limit is most likely caused by equihbrium. This limit and thus the equilibrium constant were not affected by the temperature range studied, consistent with a low heat of reaction. The sum of the molar heats of combustion of stearic acid (11320 kJ/mol) and methanol (720 kJ/mol) is almost the same as the heat of combustion of methyl stearate (12010 kJ/mol), meaning that the change in enthalpy of this reaction is nearly zero and that the equihbrium constant is essentially temperature independent. 

Calcium, magnesium, and zinc salts of stearic acid... 

Slightly different constraints are used to illustrate the mathematical technique. In this example, the constrained optimization problem is to locate levels of stearic acid (X ) and starch (X2) that minimize the time of in vitro release (y2) such that the average tablet volume (jy) did not exceed 9.422 cm2 and the average friability (y3) did not exceed 2.72%. 

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