stearic acid

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 στέαρ "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 simplesugar or corn cyrup as a hardener in candies. In fire works stearic acid is often used to coat metal powders such as  aluminium  and iron . This prevents oxidation, allowing compositions to be stored for a longer period of time.

 

Analysis of Stearic Acid

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

----

Scroll to Top