Isopropyl myristate is one of the workhorse esters of the personal care industry: cheap, light, odourless and easy to formulate with. It is also one of the most frequently mis-specified, because buyers compare it on price per kilogram while the parameters that actually decide whether a lot performs are the ester content, the acid value and the identity figures. This guide covers the molecule, what each specification item is really controlling, how it compares with the other emollient esters, and where it causes formulation problems. The specification itself is on the isopropyl myristate product page.
Identity and physical properties
| Property | Value | Practical significance |
|---|---|---|
| Chemical name | Isopropyl tetradecanoate | A saturated C14 fatty acid esterified with isopropanol |
| CAS | 110-27-0 | – |
| Formula / molecular weight | C17H34O2 / 270.45 | Small and highly lipophilic – it spreads and penetrates rather than occluding |
| INCI name | Isopropyl Myristate | The label name in every major cosmetic market |
| Appearance | Colourless to slightly yellow oily liquid | Yellowing indicates oxidation or inadequate refining |
| Solubility | Insoluble in water; miscible with ethanol, isopropanol, mineral oil and most cosmetic esters | An oil-phase ingredient with no need for a solubiliser |
| Saturation | Fully saturated | Better oxidative stability than the unsaturated esters, but not immune to ageing |
How it is made
IPM is produced by esterifying myristic acid with isopropanol, normally with an acid catalyst and with the water of reaction removed to drive the equilibrium. The commercial quality is then decided by two things: how completely the esterification is driven (which shows up as acid value and ester content) and how well the product is refined and bleached (which shows up as colour).
| Stage | What it controls | Which specification item reflects it |
|---|---|---|
| Esterification | Conversion of acid to ester | Ester content, acid value |
| Excess alcohol removal | Residual isopropanol | Odour, and the ester content figure |
| Washing and neutralisation | Residual catalyst and free acid | Acid value, colour |
| Bleaching / stripping | Colour bodies and oxidation products | Hazen colour |
| Storage | Hydrolysis and oxidation during hold | Acid value drift, colour drift |
Reading the specification
| Parameter | Limit | What it is actually controlling |
|---|---|---|
| Ester content | Min 98% | The main purity figure. A low value means unreacted acid or alcohol is still present, which affects skin feel and can raise the irritation potential |
| Acid value | Max 0.5 mg KOH/g | Free fatty acid. The single most useful indicator of both process control and storage stability – a lot whose acid value climbs has been hydrolysing |
| Colour (Hazen) | Max 30 | Matters directly in white or pale formulations; also a proxy for oxidative history |
| Refractive index (20 deg C) | 1.434 – 1.438 | Identity. An isopropyl palmitate or isopropyl laurate mix-up changes this figure before anything else does |
| Specific gravity (20 deg C) | 0.850 – 0.855 | Identity and batch consistency; used for volumetric-to-mass conversion on the production floor |
Two of these deserve emphasis. The acid value is the one number that trends over time, so watch it across deliveries rather than only on release. And the refractive index is the cheapest defence against a chain-length substitution: IPM, isopropyl palmitate and isopropyl laurate are all “isopropyl esters of fatty acids” and behave differently on skin, but only one of them matches 1.434-1.438.
What it does in a formulation
| Function | Mechanism | Where it is the point of the ingredient |
|---|---|---|
| Emollient | Fills the spaces between corneocytes and softens the surface | Lotions and creams where a light, dry skin feel is wanted |
| Spreading agent | Lowers the viscosity of the oil phase and reduces the work needed to spread the film | Sunscreens and body products, where uniform coverage determines performance |
| Penetration enhancer | Increases partitioning of actives into the stratum corneum | Topical drug delivery, and intentionally in some cosmetic actives |
| Solubiliser and carrier | Dissolves oil-soluble actives, UV filters and colourants | Where the oil phase must carry a high load of solids |
| Skin-feel modifier | Reduces the greasiness of heavier oils when blended | Tuning an oil phase that would otherwise feel heavy |
Typical applications and use levels
| Sector | Function | Typical use level |
|---|---|---|
| Skin care emulsions | Emollient and spreading agent in the oil phase | Of the order of 2-10% |
| Sun care | Solubiliser for UV filters, film uniformity | Of the order of 2-8% |
| Colour cosmetics | Binder and emollient in lipsticks and pressed powders | Recipe-dependent, often 5-20% |
| Body and baby oils | Main oil-phase component | Up to 50% or more |
| Hair care | Lubricant and conditioning ester | Of the order of 0.5-3% |
| Topical pharmaceuticals | Vehicle and penetration enhancer | Set by the formulation and the regulatory dossier |
IPM against the other emollient esters
| Emollient | Skin feel | Spreading | Where it wins | Where it loses |
|---|---|---|---|---|
| Isopropyl myristate | Light, dry, non-greasy | Good | Cost, availability, broad compatibility, sun care | Can feel slightly “oily” at high levels; not the most occlusive |
| Isopropyl palmitate (IPP) | Richer, slightly heavier | Moderate | Where more body is wanted | Slower spreading; heavier on skin |
| Isopropyl isostearate | Lighter still, very spreadable | Excellent | Premium skin feel, easy-spreading products | Higher cost |
| Caprylic/capric triglyceride | Dry and smooth | Good | Where a vegetable-derived ester is preferred | Higher cost; different solubility profile |
| Silicone (dimethicone) | Slippery, non-greasy | Very good | Film formation and slip | Not substantive to skin; can interfere with reapplication |
| Mineral oil | Heavy, occlusive | Poor | Barrier and occlusion at low cost | Greasy feel, poor spreadability, consumer perception |
| Vegetable oils | Variable, often rich | Poor to moderate | Marketing story and natural positioning | Oxidative instability; batch variability |
Formulation and compatibility notes
| Point | What to know |
|---|---|
| Emulsification | A polar oil; it needs a suitable emulsifier pair and is not self-emulsifying. It sits happily in both O/W and W/O systems with the right surfactant blend |
| Solubility of actives | Good solvent for many UV filters and oil-soluble actives; check the specific active, since solubility varies |
| Silicone compatibility | Miscible with most dimethicones, which makes it useful for adjusting the feel of silicone-heavy systems |
| Oxidation | Saturated, so more stable than unsaturated esters, but the acid value will still rise over time. Add an antioxidant where the formulation is stored warm |
| Skin feel at high loading | Above about 15-20% of the oil phase, the dry feel gives way to a distinct oiliness – blend with a lighter ester if that is a problem |
| Packaging contact | Compatible with most plastics and lined metal; check gasket materials in pumps and closures |
Buying notes
| Item | What to fix in writing |
|---|---|
| Ester content and acid value | Both figures, with the test methods, since these two decide skin feel and stability |
| Identity figures | Refractive index and specific gravity – the cheapest guard against a chain-length substitution |
| Colour | Hazen limit, and confirmation that it is measured on the neat ester |
| Grade statement | Cosmetic grade, with the market-specific declaration your labelling requires |
| Packaging | Drum or IBC, and confirmation of the liner or coating if the container is not stainless |
| Remaining shelf life | Agreed on delivery; the acid value moves during storage |
| Documentation | Batch COA with measured values, SDS, and an allergen or GMO statement if your customer requires one |
Frequently asked questions
Is isopropyl myristate the same as isopropyl palmitate?
No – they are different fatty acid chain lengths (C14 versus C16) and behave differently on skin. IPM is lighter and spreads more easily; IPP is richer. The refractive index distinguishes them quickly.
Why does the acid value matter if the ester content is already 98%?
Because they measure different things. Ester content says how much ester is present; acid value says how much free fatty acid is present. Free acid drives odour, irritation potential and further degradation, so a lot can be nominally on specification and still be drifting.
Can IPM be used in a natural-certified formulation?
Check the certification scheme. IPM is a synthetic ester even though the myristic acid may be vegetable-derived, so some natural and organic standards exclude it. Confirm against the standard you are actually certified to.
Is it suitable for sensitive skin?
IPM is widely used in leave-on products and is generally regarded as a mild emollient, but no ingredient suits every skin. The acid value and purity of the particular lot matter, and any claim about suitability belongs to the finished product’s own testing and regulatory assessment.
How should IPM be stored?
Sealed, cool and out of direct sunlight. It is a saturated ester so it is more stable than a vegetable oil, but heat and air will still raise the acid value over time.