ISOOCTADECANOIC ACID

Isooctadecanoic Acid is a branched-chain saturated C18 fatty acid commonly known as isostearic acid.
Commercial Isooctadecanoic Acid combines the hydrophobic character of a long-chain fatty acid with fluidity at room temperature, low-temperature performance, and strong resistance to oxidative deterioration.
These characteristics support its use in personal care formulations, pigment dispersions, lubricants, metalworking fluids, coatings, inks, specialty esters, and fatty-acid derivatives.

CHEMICAL IDENTITY AND COMMON NAMES

Commercial Isooctadecanoic Acid is primarily a mixture of methyl-branched, saturated C18 monocarboxylic acid isomers.
The positions and distribution of the alkyl branches influence fluidity, crystallisation behaviour, viscosity, and the performance of the resulting esters and salts.
Isooctadecanoic Acid differs from linear stearic acid because branching prevents close molecular packing and substantially lowers the solidification temperature.
It differs from oleic acid because its predominantly saturated structure provides greater resistance to oxidation, colour change, and odour development.

CAS Number 30399-84-9 identifies the commercially established mixed-isomer material.
CAS Number 2724-58-5 identifies 16-methylheptadecanoic acid, a defined positional isomer that is also indexed under the common name isostearic acid in some chemical records.
The defined positional isomer and the commercial mixed-isomer material require separate identity control in specifications and purchasing documents.

Synonyms and Common Names: Isostearic acid, Isooctadecanoic acid, isooctadecanoic acid, iso-C18 fatty acid, branched C18 fatty acid, branched-chain C18 fatty acid, branched octadecanoic acid, isomeric octadecanoic acid, mixed-isomer isostearic acid, ISAC

TECHNICAL IDENTIFICATION

CAS Number: 30399-84-9
EC / EINECS Number: 250-178-0
INCI Name: Isostearic Acid
Molecular Formula: C18H36O2
Molar Mass: 284.48 g/mol
Chemical Class: Branched-chain saturated fatty acid
Functional Group: Monocarboxylic acid
Carbon Chain Length: C18
Commercial Chemical Form: Mixture of branched octadecanoic acid isomers

The molecular formula and molar mass describe the saturated C18 monocarboxylic acid components of the mixed-isomer material.
A single structural formula does not fully represent the branch-position distribution of commercial Isooctadecanoic Acid.

PHYSICAL AND CHEMICAL PROPERTIES

Appearance: Clear oily liquid
Physical State: Liquid at room temperature
Colour: Colourless to pale yellow
Odour: Mild characteristic fatty odour
Relative Density: Approximately 0.88–0.90 at 20–25 °C
Acid Value: Commonly 180–201 mg KOH/g
Saponification Value: Commonly 185–205 mg KOH/g
Iodine Value: Common low-unsaturation grades are specified at not more than 2–8 g I2/100 g
Cloud or Solidification Point: Common mixed-isomer grades remain fluid below approximately 10 °C
Dynamic Viscosity: Approximately 35–60 mPa·s at 25 °C for common mixed-isomer grades
Kinematic Viscosity: Approximately 33 mm²/s at 40 °C for lubricant-oriented grades
Kinematic Viscosity: Approximately 6.1 mm²/s at 100 °C for lubricant-oriented grades
Refractive Index: Approximately 1.45
Flash Point: Approximately 165–204 °C, according to composition and test method
Water Solubility: Practically insoluble
Organic Solubility: Soluble in many alcohols, ketones, ethers, hydrocarbons, oils, and other organic media
Vapour Pressure: Low at ambient temperature
Volatility: Low under normal storage and processing conditions
pH: Not applicable to the neat material
Unsaturation: Low in hydrogenated and low-iodine-value grades
Oxidative Stability: High compared with unsaturated C18 fatty acids
Chemical Stability: Stable under recommended handling and storage conditions
Incompatible Materials: Strong oxidising agents and strongly reactive bases

Acid value is one of the primary controls for assessing free fatty-acid content and reaction capacity.
Iodine value indicates residual unsaturation and is particularly important when colour stability, odour stability, thermal exposure, or long service life is required.

Cloud point, solidification behaviour, and viscosity are important for low-temperature processing, pumping, metering, and lubricant performance.
Moisture, colour, unsaponifiable matter, and branch distribution provide additional controls for sensitive cosmetic, esterification, coating, and specialty-fluid applications.

FUNCTIONAL CHARACTERISTICS

The branched hydrocarbon structure of Isooctadecanoic Acid disrupts crystallisation and keeps commercial mixed-isomer grades liquid at temperatures where linear stearic acid is solid.
This fluidity simplifies pumping, blending, pigment grinding, oil-phase incorporation, and low-temperature handling.

The saturated carbon chain provides better resistance to oxidative degradation than unsaturated fatty acids such as oleic acid.
Low residual unsaturation supports improved colour retention, reduced odour development, and longer functional life in formulations exposed to heat, air, or extended storage.

The long hydrocarbon chain provides oil solubility, hydrophobicity, surface substantivity, and boundary lubrication.
The carboxylic acid group enables neutralisation, salt formation, esterification, amidation, adsorption onto polar surfaces, and interaction with metal substrates.

Branching produces derivatives with lower crystallisation tendencies and improved fluidity.
Isooctadecanoic Acid is therefore valuable as both a functional ingredient and a chemical building block for specialty esters, metal soaps, surfactants, emulsifiers, corrosion-control additives, and resin modifiers.

PRODUCTION AND COMMERCIAL FORM

Isooctadecanoic Acid is produced from unsaturated C18 fatty-acid feedstocks through catalytic skeletal isomerisation followed by hydrogenation, separation, and purification.
Commercial material may also be recovered from the branched monomer fraction generated during dimer-acid production.

Catalytic isomerisation redistributes the carbon skeleton and forms methyl-branched C18 structures.
Hydrogenation reduces residual unsaturation, while distillation and fractionation control acid value, colour, odour, low-temperature behaviour, and the content of linear fatty acids and unsaponifiable matter.

Commercial Isooctadecanoic Acid is generally supplied as a clear, low-colour liquid.
Vegetable-derived, low-iodine-value, cosmetic-oriented, lubricant-oriented, and industrial grades are selected according to feedstock origin, isomer composition, colour, purity, moisture, and performance requirements.

APPLICATIONS AND INDUSTRIES

Personal care and cosmetics

Isooctadecanoic Acid functions as an emollient, skin-conditioning ingredient, binding agent, oil-phase component, and formulation stabiliser in personal care products.
Its branched structure provides smooth spreading, a soft skin feel, substantivity, gloss, and water-repellent character without the waxy behaviour associated with linear stearic acid.

Isooctadecanoic Acid is used in creams, lotions, facial products, lip products, foundations, mascaras, eye cosmetics, sunscreens, and other anhydrous or emulsified formulations.
Its liquid state assists cold processing and oil-phase incorporation, while its oxidative stability supports colour and odour retention during storage.

In colour cosmetics, Isooctadecanoic Acid wets mineral and organic pigments and helps distribute them throughout the oil phase.
Effective pigment wetting can improve dispersion uniformity, colour development, gloss, product smoothness, and resistance to pigment agglomeration.

The carboxylic group permits partial or complete neutralisation with suitable alkalis or amines.
The resulting isostearate soaps can contribute to emulsification, consistency, cleansing, surface activity, and deposition.

Cosmetic esters and specialty emollients

Isooctadecanoic Acid is an important feedstock for liquid isostearate esters used as emollients, spreading agents, binders, pigment dispersants, and oil-phase modifiers.
Esterification with monofunctional alcohols produces fluid esters with adjustable polarity, viscosity, spreadability, and sensory characteristics.

Reaction with polyols produces multifunctional esters used where richer texture, film formation, gloss, pigment wetting, or water resistance is required.
The branched C18 group reduces orderly crystallisation and helps the resulting esters remain fluid across a broader temperature range.

Low colour, low odour, low moisture, and low residual unsaturation are especially important when Isooctadecanoic Acid is used to manufacture high-quality cosmetic esters.
A high acid value and controlled unsaponifiable content support predictable reaction stoichiometry, conversion, purification, and final ester quality.

Lubricants and functional fluids

Isooctadecanoic Acid is used as a boundary lubricant, emulsifier, corrosion-control component, and synthetic-ester feedstock in lubricant systems.
The polar carboxylic group can adsorb onto metal surfaces, while the hydrocarbon chain provides a lubricating film that reduces direct surface contact.

The branched structure supports low-temperature fluidity and reduces crystallisation in lubricant formulations and derived esters.
Its predominantly saturated structure also provides greater oxidation resistance than comparable materials based on unsaturated fatty acids.

Polyol and complex esters produced from Isooctadecanoic Acid are used in synthetic lubricants requiring fluidity, lubricity, thermal stability, and controlled viscosity.
Alcohol and polyol selection determines the final ester’s viscosity, volatility, hydrolytic behaviour, seal compatibility, and low-temperature performance.

Metalworking and metal-forming fluids

Isooctadecanoic Acid is used in metalworking concentrates, rolling oils, cutting fluids, drawing compounds, and forming lubricants.
It provides boundary lubrication, emulsification support, metal-surface affinity, and corrosion inhibition.

In water-dilutable systems, neutralised Isooctadecanoic Acid forms surface-active soaps that assist emulsification and metal wetting.
The neutralising agent, degree of neutralisation, water hardness, electrolyte content, and concentrate composition determine emulsion stability and corrosion performance.

Low-single-digit treatment levels are commonly evaluated in metalworking formulations.
The optimum concentration is established through emulsion stability, corrosion, lubricity, foaming, residue, and metal-staining tests for the intended operation.

Greases and metal soaps

Isooctadecanoic Acid reacts with metal bases to produce isostearate soaps used as grease components, liquid stabilisers, water-repellent agents, and specialty additives.
Branching can modify soap solubility, thickening behaviour, consistency, and low-temperature response compared with linear stearates.

The acid may be incorporated during in-situ soap formation or used to prepare a separate metal isostearate.
Acid value, branch distribution, moisture, and unsaponifiable matter affect neutralisation, soap formation, grease texture, and storage stability.

Coatings and resin modification

Isooctadecanoic Acid is used as a building block and modifier in polyester, polyamide, alkyd-related, and specialty coating-resin chemistry.
Its long branched chain introduces flexibility, hydrophobicity, pigment affinity, and resistance to brittle crystallisation.

Resin modification with Isooctadecanoic Acid can improve film flexibility and help coatings accommodate deformation on flexible or stressed substrates.
Its saturated structure also supports thermo-oxidative stability and colour retention in coatings exposed to elevated temperatures or prolonged service.

Low-colour grades are important for white, pale, transparent, and colour-sensitive coatings.
Acid value, iodine value, moisture, and residual impurities affect polymerisation, molecular-weight development, cure behaviour, film appearance, and ageing performance.

Printing inks and pigment concentrates

Isooctadecanoic Acid is used in printing inks, pigment concentrates, and metallic pastes as a wetting aid, dispersing component, lubricant, and resin-compatible modifier.
Its polar acid group interacts with pigment or metal surfaces, while the branched hydrocarbon portion remains compatible with organic vehicles.

Improved pigment wetting can increase colour strength, gloss, dispersion stability, and achievable pigment loading.
The liquid state also facilitates dosing and incorporation into pigment-grinding stages.

Metallic pastes require careful control of moisture, acidity, and compatibility with the selected metal.
Low moisture and a controlled acid profile help maintain paste stability and processing consistency.

Waxes, emulsions, and surface treatments

Isooctadecanoic Acid and its salts are used in wax emulsions and hydrophobic surface-treatment systems.
The branched chain contributes lubricity, water repellency, film flexibility, and compatibility with organic wax phases.

Neutralised derivatives provide emulsification and dispersion functions in aqueous systems.
The choice of counterion and neutralisation level controls water dispersibility, emulsion particle characteristics, film formation, and surface feel.

Textile chemicals

Isooctadecanoic Acid serves as a feedstock for cationic and quaternary derivatives used in textile softeners, antistatic agents, and fibre-treatment formulations.
The long hydrophobic chain provides softness and surface lubrication, while the functionalised polar group promotes interaction with fibres and formulation media.

Branching helps derived textile auxiliaries resist crystallisation and maintain fluidity.
Colour, odour, active content, and residual acidity are important selection parameters for textile-finishing applications.

Chemical intermediates

Isooctadecanoic Acid undergoes reactions typical of long-chain carboxylic acids and is used to manufacture esters, amides, soaps, corrosion inhibitors, surfactants, stabilisers, and resin intermediates.
Its branched structure is retained in these derivatives and is used to introduce hydrophobicity, flexibility, liquidity, and oxidative stability.

Reaction partners and processing conditions determine the polarity, molecular weight, viscosity, surface activity, and end-use performance of the derivative.
High acid value, low moisture, and controlled composition support efficient conversion and consistent product quality.

GRADE SELECTION AND PRODUCT SUITABILITY

Cosmetic and personal care grades emphasise low colour, mild odour, low residual unsaturation, controlled composition, and suitable purity.
Relevant parameters include acid value, iodine value, saponification value, moisture, unsaponifiable matter, colour, appearance, traceability, and cosmetic documentation.

Ester-manufacturing grades require predictable carboxylic functionality and low levels of water and non-reactive impurities.
A high and consistent acid value supports accurate alcohol-to-acid stoichiometry, while low moisture assists reaction control and water removal.

Lubricant and metalworking grades are selected according to low-temperature fluidity, viscosity, iodine value, thermal stability, emulsification response, corrosion performance, and metal compatibility.
Branch distribution and residual linear fatty-acid content can influence cloud point, pour behaviour, and the properties of derived esters or soaps.

Coating, ink, and pigment-dispersion grades require suitable colour, oxidative stability, viscosity, pigment wetting, and compatibility with the resin or carrier phase.
Low iodine value is particularly valuable in formulations where heat, light, or air exposure can cause colour or odour deterioration.

Vegetable-derived grades support formulations with renewable feedstock requirements.
Feedstock origin, manufacturing route, identity, composition, and certification status form part of the relevant procurement documentation.

FORMULATION AND PROCESS CONSIDERATIONS

Isooctadecanoic Acid is incorporated directly into oil phases, resin systems, lubricant concentrates, pigment grinds, or esterification reactions.
Its negligible water solubility means direct addition to an aqueous phase does not produce a molecular solution.

For emulsions, Isooctadecanoic Acid may be combined with compatible surfactants or neutralised to form a water-dispersible isostearate soap.
Neutralisation level affects pH, emulsion structure, viscosity, surface activity, and storage stability.

For pigment dispersion, Isooctadecanoic Acid is normally introduced into the liquid carrier before or during pigment wetting.
Uniform pre-wetting followed by controlled high-shear mixing or milling helps reduce agglomerates and develop colour strength.

For esterification, Isooctadecanoic Acid reacts with an alcohol or polyol while the water of reaction is removed.
Temperature, catalyst, vacuum, reaction time, stoichiometry, and final acid value are controlled according to the selected ester and purification process.

Material that becomes hazy or partially solid after cold storage can be restored to homogeneity by gentle warming and mixing.
Localized overheating should be avoided to protect colour and prevent unnecessary thermal exposure.

QUALITY, SPECIFICATIONS AND DOCUMENTATION

Acid value measures free carboxylic functionality and supports identity, purity, neutralisation, and esterification calculations.
A result close to the theoretical value for a C18 monocarboxylic acid indicates a high proportion of reactive fatty acid.

Iodine value measures residual unsaturation.
Low iodine value supports oxidative stability, odour control, colour retention, and thermal ageing performance.

Saponification value assists identity and composition control and can indicate the presence of esterifiable or saponifiable components.
Comparison of acid and saponification values provides useful information about neutral impurities, ester content, and overall product character.

Cloud point, solidification point, and viscosity are important for storage, pumping, low-temperature processing, and lubricant applications.
Colour and odour are critical for cosmetics, light-coloured coatings, clear esters, and sensitive finished products.

Moisture affects esterification equilibrium, soap production, hydrolytic processing, metallic-paste stability, and storage quality.
Unsaponifiable matter influences reaction yield, residue, film properties, and the purity of derived products.

A procurement package may include a Technical Data Sheet, Safety Data Sheet, Certificate of Analysis, compositional information, origin statement, and application-specific documentation.
The Certificate of Analysis should report the batch parameters that determine performance in the selected application.

SAFETY AND REGULATORY CONSIDERATIONS

Concentrated Isooctadecanoic Acid can irritate the skin and eyes.
Protective gloves and eye protection are appropriate during sampling, transfer, formulation, and equipment cleaning.

Low vapour pressure limits inhalation exposure at room temperature, although heated vapour, mist, or aerosol can irritate the respiratory tract.
Ventilation and closed-transfer practices reduce exposure during elevated-temperature processing.

Isooctadecanoic Acid is combustible at sufficiently high temperatures.
The material should be kept away from ignition sources, excessive heat, hot surfaces, and strong oxidising agents.

Spilled material creates a slippery surface.
Leaks should be contained, collected with a suitable inert absorbent, and prevented from entering drains or surface water.

Cosmetic, industrial, and specialty applications require a grade supported by the identity, purity, traceability, safety, and regulatory documentation applicable to the intended market and use.
Finished formulations should be designed to remain non-irritating and non-sensitising under their intended conditions of use.

FIRST AID

Inhalation: Move the affected person to fresh air and keep the person comfortable for breathing.
Inhalation: Obtain medical attention if coughing, breathing difficulty, or irritation persists.
Skin Contact: Remove contaminated clothing and wash the affected skin thoroughly with soap and water.
Skin Contact: Obtain medical attention if redness, pain, or irritation persists.
Eye Contact: Rinse cautiously with clean water for at least 15 minutes while holding the eyelids open.
Eye Contact: Remove contact lenses when present and easy to do, then continue rinsing.
Eye Contact: Obtain medical attention if irritation persists.
Ingestion: Rinse the mouth and do not induce vomiting.
Ingestion: Obtain medical advice if a significant quantity has been swallowed or symptoms develop.
Note to Physicians: Provide symptomatic and supportive treatment.

HANDLING AND STORAGE

Handle Isooctadecanoic Acid with equipment and transfer lines suitable for long-chain fatty acids.
Avoid contact with the skin and eyes and prevent the formation of heated mist or aerosol.

Keep containers tightly closed in a cool, dry, well-ventilated area.
Protect the material from direct sunlight, strong oxidising agents, ignition sources, and unnecessary prolonged heating.

Cold conditions may cause haze, increased viscosity, or partial solidification.
Gentle warming with uniform mixing restores the liquid to a homogeneous condition.

Use clean, dry equipment to prevent contamination by water, incompatible chemicals, metals, pigments, or other fatty acids.
Maintain suitable housekeeping because small spills can make floors and working surfaces slippery.

PACKAGING AND PROCUREMENT CONSIDERATIONS

Isooctadecanoic Acid is commonly supplied in drums, intermediate bulk containers, and bulk deliveries.
Packaging selection depends on order quantity, unloading facilities, storage temperature, production scale, and contamination-control requirements.

Procurement specifications should identify CAS Number 30399-84-9 when the required material is commercial mixed-isomer Isooctadecanoic Acid.
The specification should also state the required acid value, iodine value, saponification value, colour, moisture, cloud point, viscosity, origin, packaging, and application-specific documentation.

For esterification, the priority parameters are acid value, moisture, unsaponifiable matter, colour, and composition.
For cosmetics, low colour, low odour, traceability, purity, and cosmetic documentation are central selection criteria.
For lubricants and metalworking fluids, low-temperature behaviour, viscosity, oxidation resistance, emulsification, corrosion performance, and metal compatibility receive greater emphasis.
For coatings, inks, and pigment systems, colour, pigment wetting, resin compatibility, residual unsaturation, and thermal stability are especially important.

For Isooctadecanoic Acid grade selection, specifications, documentation, packaging, application support, and supply requirements, contact Ataman Kimya at +90 216 577 10 10 or info@atamankimya.com