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Isostearic Acid

Definition - What does Isostearic Acid mean?

Isostearic acid is a fatty acid molecule with an 18-carbon atom chain backbone. It is an isomer of stearic acid, meaning that they both have a chemical formula of C18H36O2, but differ in the arrangement of their atoms. While stearic acid has a linear carbon chain with 18 carbon atoms, isosteric acid as a carbon chain with 17 atoms and a single carbon branch at the 16th carbon atom. Its chemical structure can be represented as (CH3)2CH(CH2)14CO2H. It is found naturally in meat products and vegetable oils.

Isostearic acid has a wide range of industrial uses. It is mainly used as an additive in adhesives or lubricants for both paints and personal care products.

Corrosionpedia explains Isostearic Acid

The slight structural difference between isostearic acid and its isomer, stearic acid, changes the physical state at room temperature and pressure. Although stearic acid is solid, isostearic acid is a clear yellow liquid. This is because the branching nature of isostearic acid’s carbon chain makes the molecules unable to pack as efficiently in the solid state as in the non-branching stearic acid. Less efficient packing relatively lowers the melting point. Some other basic properties include:

  • Molecular mass: 284.48 g/mol
  • Density (at 25°C): 0.89 g/cm3

Being a fatty acid, isostearic acid is also amphiphilic, meaning it is a molecule with a hydrophobic end and a hydrophilic end. As such, isostearic acid can have favorable interactions with both polar and non-polar molecules, enabling it to act as a surfactant. It is also soluble in many oils, which allows it to be used as an emulsifier or dispersant. With this set of properties, isostearic acid is a useful additive in a variety of applications, including:

  • Adhesives
  • Coatings and paints
  • Finishing agents
  • Lubricants
  • Sealants
  • Solvents
  • Surfactants
  • Viscosity adjusters

Consumer uses include personal care products and cosmetics, which take advantage of the lubricating or adhesive properties of isostearic acid. It is also used in paper products.

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