Stearic Acid Used in Soaps, cosmetics, detergents
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Stearic acid?is a saturated?fat full?acid with an 18-carbon chain
It is a?waxy?solid product from refinery and its chemical formula is C17H35CO2H. Its name comes from the Greek?word στ?αρ “stéar“, which means tallow .?Salts and esters?of stearic acid are called?stearates. Stearic acid is one of the most common saturated fatty acids found in nature following palmitic acid. Triglyceride derived from three molecules of stearic acid is called stearin .
Stearic acid is derived from fats and oils by the saponification?of the triglycerides using hot water (about 100?°C). The resulting mixture will be then distilled.?Commercial stearic acid is often a mixture of stearic and palmitic acid .although purified stearic acid is also available.
Fats and oils rich in stearic acid are more abundant in animal type fat (up to 30%) than in vegetable fat (typically <5%). The important exceptions are the foods cocoa butter .
In terms of its biosynthesis, stearic acid is produced from carbohydrates via the fatty acid .
In general, the applications of stearic acid exploit its functional character, with a polar head group and a nonpolar chain that confers solubility in organic solvents. The combination leads to uses as a surfactant and softening agent. Stearic acid undergoes the typical reactions of saturated carboxylic acids, and esterification with a range of alcohols. This is used in a large range of manufactures, from simple to complex electronic devices.
In Human diet
The fatty acids are absorbed in the regular diet the same as the free fatty acids. Low acute toxicity is shown. There was in 2017 no evidence at doses up to 10% in the diet for toxic effects.
Used in Soaps, cosmetics, detergents
Stearic acid is mainly used in the production of detergents, soaps, and?cosmetics?such as shampoo?and shaving cream??products. Soaps are not made directly from stearic acid, but indirectly by saponification?of triglycerides consisting of stearic acid esters.Esters?of stearic acid with ethylen glycol , glycol stearate??are used to produce a pearly effect in shampoos, soaps, and other cosmetic products. They are added to the product in molten form and allowed to crystallize under controlled conditions. Detergents are obtained from amides.
Lubricants, softening and release agents
In view of the soft texture of the sodium salt, which is the main component of soap, other salts are also useful for their lubricating properties. Lithium stearate?is an important component of grease. The stearate salts of zinc, calcium, cadmium, and lead are used to soften PVC. Stearic acid is used along with castor oil for preparing softeners in textile sizing. They are heated and mixed with caustic potash or caustic soda. Related salts are also commonly used as release agents?e.g. In the production of automobile tires
Being inexpensive and chemically benign, stearic acid finds many niche applications. As an example, it can be used to make?castings from a plaster?piece mold?or?waste mold. In this use, powdered stearic acid is mixed in water and the suspension is brushed onto the surface to be parted after casting. This reacts with the calcium in the plaster to form a thin layer of calcium starate??which functions as a release agent. When reacted with zinc?it forms zinc steartae?which is used as a lubricant?for playing cards fanning powder?to ensure a smooth motion when fanning .
Stearic acid is used as a negative plate additive in the manufacture of lead-acid batteries. It is added at the rate of 0.6 g per kg of the oxide while preparing the paste. It is believed to enhance the hydrophobicity??of the negative plate, particularly during dry-charging process. It also reduces the extension of oxidation of the freshly formed lead (negative active material) when the plates are kept for drying in the open atmosphere after the process of tank formation.
Fatty acids are classic components of candle-making. Stearic acid is used along with simple sugar?or corn cyrup?as a hardener in candies. In fire works stearic acid is often used to coat metal powders such as?aluminum??and iron .?This prevents oxidation, allowing compositions to be stored for a longer period of time.
Analysis of Stearic Acid
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CHARACTERISTIC
RESULT
METHOD
Iodine?Value
Max. 1.5
ISIRI 4886
Melting?Point
58-62?C
ISIRI 4887
Acid?Value
195-207
ISIR?4178
Stearic?Acid
70-75?wt%
ISIR?4090-4091
Palmitic?Acid
25-30?wt%
ISIR 4090-4091
Appearance
Flake
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