You spec “dimethicone” for a body lotion, a release coating, and a damping fluid, and the supplier asks the question that decides everything before it quotes: which viscosity? Dimethicone ships as anything from a thin fluid that spreads like a solvent to a heavy oil you pour slowly, and every grade is the same polymer. Pick the wrong one and it migrates off the part, drags, leaves the wrong after-feel, or never wets the surface. This guide is written for personal-care, coatings, and lubricant formulators and the procurement teams buying for them.
The short version. Dimethicone is the INCI name for polydimethylsiloxane (PDMS), CAS 9016-00-6: a polymer built from a repeating [-Si(CH₃)₂-O-] unit, an inorganic silicon-oxygen backbone carrying two methyl groups on every silicon. In a formula it functions as a slip and spreading agent, film former, conditioning agent (by physical deposition), lubricant, release agent, water-repellent treatment, and defoamer active. Those functions all follow from a few physical properties: low surface tension (around 20-21 mN/m), an exceptionally flexible chain, water repellency, and thermal and oxidative stability to roughly 200 °C in air. The one variable you actually buy on is viscosity, measured in centistokes (cSt) and set by chain length. Match the grade to the function.
What dimethicone actually is
Dimethicone and polydimethylsiloxane are two names for one material. PDMS is the materials-science and industrial name; dimethicone is the INCI name used on personal-care ingredient labels for the fully methylated, trimethylsiloxy-terminated PDMS homopolymer. Both share CAS 9016-00-6 and appear on PubChem under dimethicone, dimethylpolysiloxane, and PDMS. Structurally it is a linear chain of dimethylsiloxane units: each silicon atom bonds to two backbone oxygens and two methyl (–CH₃) groups, and the chain ends are capped with trimethylsiloxy groups.
The end-group is what the name pins down. “Dimethicone” specifically means the trimethylsiloxy-terminated homopolymer. Change the end-group and the INCI name changes: hydroxyl-terminated PDMS is dimethiconol, not dimethicone. One chemistry covers a wide range of physical forms, because the number of repeat units (the degree of polymerization) sets the molecular weight, and molecular weight sets viscosity. Short chains give a thin fluid; long chains give a heavy oil; the longest chains give a gum. So naming the polymer does not specify the product. Always pair the name with a viscosity grade, because that is what determines behavior. For the full chemistry, see our pillar on what polydimethylsiloxane is.
The physical properties that drive its functions
Nearly every function dimethicone performs traces back to the siloxane backbone and the methyl groups on it.
- Low surface tension (~20-21 mN/m). Well below water and most organic oils. This is why it spreads and wets readily, lubricates, releases, and ruptures foam films.
- Chain flexibility. The Si-O-Si linkage is long, wide-angled, and almost free to rotate, giving a glass transition near -120 °C, so the fluid stays mobile across a wide temperature span.
- Water repellency. The outward-facing methyl shell is non-polar and hydrophobic, so the fluid sheds water and works as a water-repellent surface treatment. It is insoluble in water and disperses or dissolves only in select organic solvents.
- Thermal and oxidative stability. The partly inorganic backbone holds up thermally to roughly 200 °C in air for extended service before the methyl groups begin to oxidize.
- Chemical inertness and dielectric character. It is inert toward many acids, bases, and polar solvents and carries almost no electrical charge, which makes it useful as a dielectric and heat-transfer fluid.
Here is the honest trade-off the catalog number hides: that 200 °C figure is a ceiling, not a guarantee. Above it in air, the methyl groups oxidize and crosslink, viscosity climbs, and the fluid can gel. The real limit depends on grade, atmosphere, and exposure time. Qualify the fluid at your actual service temperature rather than trusting a single number.
Viscosity grades: one polymer, many behaviors
Viscosity is the spec that matters, reported in centistokes at 25 °C and spanning several orders of magnitude. The table maps the common bands to function. A deeper breakdown lives in our silicone oil viscosity guide.
| Viscosity (cSt at 25 °C) | Character | Typical formulation function |
|---|---|---|
| ~5–50 | Light, fast-spreading, thin film | Light slip and spreadability, low-residue release, formulation carrier |
| ~100–350 | Medium-light, balanced spread and film | General slip and lubrication, antifoam base, personal-care after-feel |
| ~1,000 | Medium body, good film build and lubricity | Lubricants, damping fluids, dielectric coolant, durable slip film |
| ~5,000–60,000 | Heavy, slow-flowing | Damping, heavy lubrication, thick release and barrier films |
| ~100,000+ | Gum-like, barely pourable | Elastomer and sealant feedstock, viscosity-building additive |
The pattern is consistent: lower viscosity buys volatility-adjacent spreading and a thinner residual film; higher viscosity buys film thickness, drag, and persistence. No single grade does both, which is the whole reason the family exists as a ladder. The reliable move is to bracket your best guess with the grade above and below it, request samples, and test both on your own system.
Formulation functions across industries
The same polymer recurs in a handful of roles. Each is a physical or formulation function, not a health or cosmetic-benefit claim.
Personal-care formulation. Under the INCI name dimethicone, PDMS is valued for slip, even spreadability, and a dry, non-greasy after-feel in lotions, color cosmetics, and hair products, and for forming a thin continuous film over the substrate. In hair and skin formulas it acts as a conditioning agent by physical deposition — the low-surface-tension fluid spreads and lays down a smoothing film that reduces surface friction and adds gloss. In makeup it improves spreadability and pigment dispersion and contributes a uniform film. These describe what the material does physically in a formula at the beauty and personal care bench; they are not statements about skin or hair health.
Coatings. Low surface tension makes dimethicone a slip, leveling, and mar-resistance additive and a defoaming active in coatings. The same property is a double-edged tool: over-dosed or poorly matched silicone can cause craters and fisheyes in a paint film. Dose low and qualify on your real substrate before scaling.
Lubrication. As a low-friction lubricant for plastic-on-plastic, rubber, and elastomer contacts, dimethicone offers shear stability and a steady film across a wide temperature range. The 1,000 cSt grade is a common workhorse for industrial manufacturing lubrication, damping, and dielectric duty.
Release. Because the methyl surface is low-energy and inert, cured resins, rubbers, and adhesives do not bond to it, so dimethicone releases molded parts cleanly. Lighter grades leave a thinner residual film where downstream painting or bonding matters.
Defoaming. PDMS is the active ingredient in most silicone defoamers. Its low surface tension lets droplets spread across the foam lamella and destabilize it, typically compounded with hydrophobic silica or supplied as an aqueous emulsion for water-based systems.
Textile and water-repellent finishing. The hydrophobic methyl shell imparts water repellency and a softer hand to fabrics, which is why silicone fluids and their emulsions are used as textile softeners and water-repellent treatments.
Dimethicone versus related silicones
Formulators rarely choose dimethicone in isolation; they choose it against its siblings. The distinctions are physical, and they decide where each fits.
| Material | How it differs physically | Where the difference points |
|---|---|---|
| Dimethicone (PDMS) | Linear, fully methylated, non-volatile across most grades; persistent film | Durable slip, film, lubrication, release |
| Cyclopentasiloxane (cyclomethicone) | Cyclic, volatile siloxane that evaporates and leaves little residue | Light, fast-spreading carrier; dry after-feel where no residual film is wanted |
| Dimethiconol | Hydroxyl-terminated PDMS, higher viscosity, more substantive film | Heavier conditioning film and longer persistence |
| Amodimethicone | Amine-functional; the charged groups give it substantivity to negatively charged substrates | Conditioning agent that deposits and persists on fibers and hair; textile softening |
| PEG-12 Dimethicone | PEG-grafted, water-dispersible silicone surfactant | Emulsifier and wetting agent that carries silicone into the water phase |
The honest tension is volatility versus persistence. Cyclopentasiloxane flashes off and leaves a dry feel but no lasting film; dimethicone stays and builds a durable film but can feel heavier at high viscosity. Amino-functional and PEG-modified grades exist precisely because unmodified dimethicone neither deposits selectively onto a charged substrate nor disperses into water on its own. Pick the variant whose physical behavior matches the result you need, then confirm it in the finished formula.
Grades, specs, and bulk sourcing
Dimethicone is specified primarily by viscosity grade (cSt at 25 °C), with end-group and any functionalization (amino, PEG, hydroxyl) as the next decisions. Typical physical reference points are a clear, colorless, essentially odorless fluid that is insoluble in water; exact viscosity, volatiles, and refractive index are lot-specific and governed by the Certificate of Analysis (CoA), not by a catalog figure.
RawSource supplies dimethicone and the broader silicone-fluid range from domestic US stock for personal care and industrial manufacturing formulators: standard dimethicone viscosity grades, the 1,000 cSt silicone oil workhorse, amino-functional amodimethicone, and water-dispersible PEG-12 Dimethicone — in drums, IBCs, and bulk, with CoA documentation. For an RFQ, tell us the target viscosity grade, the end use (personal care, coatings, lubrication, release, or antifoam), whether your system is water- or solvent-based, and your volume, and request a sample to qualify the grade on your own line.
Frequently asked questions
Is dimethicone the same as polydimethylsiloxane (PDMS)?
Yes. Dimethicone is the INCI (personal-care label) name for the fully methylated, trimethylsiloxy-terminated PDMS homopolymer, and both names share CAS 9016-00-6. PDMS is the industrial and materials-science name for the same polymer. Change the end-group and the INCI name changes too: hydroxyl-terminated PDMS is dimethiconol.
What viscosity grade of dimethicone do I need?
Work backward from the function. Light grades (about 5–50 cSt) give fast spreading and a thin film for slip and low-residue release; 100–1,000 cSt covers general lubrication, release, and personal-care after-feel; 5,000–60,000 cSt is for damping and heavier films; gum grades feed elastomers and sealants. Bracket your best guess with the grade above and below and test both on your own system.
What is the function of dimethicone in a formulation?
It acts as a slip and spreading agent, a film former, a conditioning agent by physical deposition, a lubricant, a release agent, a water-repellent treatment, and a defoamer active. These functions follow from its low surface tension, chain flexibility, water repellency, and thermal and oxidative stability.
Is dimethicone water-soluble?
No. Unmodified dimethicone is insoluble in water and disperses only in select organic solvents. To carry silicone into a water phase, formulators use a water-dispersible silicone surfactant such as PEG-12 Dimethicone or a pre-made silicone emulsion rather than neat dimethicone.
How is dimethicone different from cyclopentasiloxane?
Cyclopentasiloxane (cyclomethicone) is a volatile cyclic siloxane that evaporates and leaves little residue, so it is used where a light, fast-spreading carrier and a dry feel are wanted with no lasting film. Dimethicone is non-volatile across most grades and builds a durable film, so it is used for persistent slip, lubrication, and release.
What is the difference between dimethicone and amodimethicone?
Amodimethicone is an amine-functional silicone. The charged amino groups give it substantivity to negatively charged substrates such as fibers and hair, so it deposits selectively and persists where unmodified dimethicone would not. That makes it a conditioning agent in personal care and a softener in textiles, while plain dimethicone is the general-purpose, non-functionalized fluid.
Editorial note. This article is general technical guidance for personal-care, coatings, lubricant, and industrial formulation professionals. Dimethicone performance depends on the specific viscosity grade, end-group, functionalization, formulation, dose, substrate, and service temperature, and must be validated on your own system; the Certificate of Analysis governs the grade you buy. Review the current Safety Data Sheet (SDS) and use appropriate handling practices before use. Products are sold for industrial and professional use only. Nothing here is a medical, health, cosmetic-benefit, or safety claim. RawSource makes no warranty, express or implied, and assumes no liability for use of this information.
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