What Is Hydrogenated Polyisobutene?
Hydrogenated polyisobutene, often shortened to hydrogenated PIB, is a fully saturated synthetic hydrocarbon polymer. It is produced by polymerising isobutene into polyisobutene and then hydrogenating the polymer chain, a step that converts the residual double bonds into single bonds. That saturation is what separates it from ordinary polyisobutene: the hydrogenated grade resists oxidation far better, does not yellow during storage and stays inert when it meets other formulation ingredients. The commercial product is a clear, colourless, practically odourless liquid with a smooth, non-tacky feel and a viscosity that is set during manufacture.
Because the material is a single-component polymer rather than a blended oil, batch-to-batch consistency in viscosity, colour and water content is straightforward to control, which makes it easy to reformulate without re-running stability work.
Physical and Chemical Properties
As a polymer, hydrogenated polyisobutene is described by ranges and grade-dependent values rather than one fixed set of numbers. The table below lists the properties that buyers normally write into a purchase specification.
| Property | Typical description |
|---|---|
| Appearance | Clear, colourless to water-white liquid, essentially odourless |
| Chemical structure | Saturated branched polyolefin derived from isobutene, with no measurable residual unsaturation |
| CAS number | 68937-10-0 |
| Density | Close to that of light mineral oil, so it blends without large density mismatch |
| Viscosity | Supplied in several grades, from low-viscosity fluids to high-viscosity, syrup-like products |
| Water solubility | Practically insoluble; freely compatible with many non-polar oils and silicone fluids |
| Oxidation stability | High; acidity and colour remain stable under normal storage conditions |
| Volatility | Very low; the material does not evaporate readily at ambient temperature |
| Reactivity | Non-reactive with most common cosmetic, lubricant and industrial ingredients |
Main Applications
Emollient and skin-conditioning agent: hydrogenated polyisobutene spreads evenly and leaves a light, breathable film that slows moisture loss without a heavy, occlusive after-feel. It appears in lotions, creams, cleansing balms and body butters.
Carrier and spreading aid: the fluid carries pigments, mineral filters and other dispersed actives, helping them distribute uniformly over skin, hair and lip surfaces.
Gloss and colour enhancer: in lip products, pressed powders and hair serums it lifts shine and reduces the whitening that powdery ingredients can cause.
Lubricant base fluid and additive: in the lubricant industry it improves the lubricating performance of other base oils and lowers friction between moving parts in lightly to moderately loaded assemblies.
Process and carrier fluid: its low volatility and non-reactive nature also suit it to industrial and agrochemical formulations where the carrier must not react with the active substance.
Hydrogenated PIB Compared with Standard Polyisobutene
| Property | Standard polyisobutene | Hydrogenated polyisobutene |
|---|---|---|
| Residual double bonds | Present | Essentially eliminated by hydrogenation |
| Oxidation resistance | Moderate | High |
| Colour stability on storage | May darken over time | Remains water-white |
| Odour | Faint olefinic note | Practically odourless |
| Typical end use | Adhesives, sealants, lubricant additives | Personal care, lubricants, carrier fluids |
Where a formulation has to stay colour-stable and odour-free for a long shelf life, the hydrogenated grade is normally the preferred choice, even though its cost per kilogram is higher than the unsaturated material.
Quality Control, Packaging and Storage
Purchase specifications usually fix viscosity, colour, water content and ash, and expect those figures to be repeated on the certificate of analysis for every lot. Incoming inspection should confirm the viscosity grade against the reference sample, since two lots with the same nominal viscosity can still feel different on skin if the molecular weight distribution differs.
Store in sealed original containers, away from direct sunlight, strong oxidising agents and ignition sources.
Keep drums and intermediate bulk containers closed when not in use; no special temperature control is needed, although prolonged heating should be avoided.
Packaging is normally in standard steel or high-density polyethylene drums and intermediate bulk containers, with small-batch and sub-packaged quantities available for trials.
When stored correctly in unopened containers the product remains stable for an extended period, and a retest date is normally quoted on the certificate of analysis.
Frequently Asked Questions
Q: Is hydrogenated polyisobutene the same as polyisobutene?
No. Both start from the same isobutene polymer, but hydrogenated polyisobutene has been treated with hydrogen so that the residual double bonds are saturated. The result is a more oxidation-resistant, more colour-stable and less odorous liquid.
Q: Is hydrogenated polyisobutene safe for skin contact?
The material has low toxicity and is not regarded as a skin sensitiser in normal use. It stays largely on the surface of the skin rather than penetrating deeply, which is why it is widely used in leave-on personal care products.
Q: How is the right viscosity grade chosen?
Low-viscosity grades give a lighter feel and faster spreading, while higher-viscosity grades build a heavier film and add body to a formulation. The grade is chosen by matching the required sensory profile and film thickness, then confirming it in stability testing.
Q: Can it be used in lubricant formulations?
Yes. It is used as a base fluid and as an additive component where low volatility, good oxidation stability and clean friction behaviour are required.
Q: How should the material be stored?
Keep containers closed in a cool, dry, ventilated area away from sunlight, oxidisers and heat sources. Under these conditions the product is stable, and the retest date on the certificate of analysis should be observed.
Q: What documentation is supplied with a shipment?
Lots are normally accompanied by a certificate of analysis, a safety data sheet and the commercial shipping documents, so that the receiving laboratory can confirm the specified viscosity, colour and water content.