Sodium dodecylbenzenesulfonate, universally abbreviated to SDBS and also called LAS-Na, is the sodium salt of linear alkylbenzene sulfonic acid and the single most widely used anionic surfactant in the world. It is the surfactant that made synthetic laundry powder possible, and it remains the benchmark against which every other anionic is judged on cost, detergency and handling.
This guide covers the identity of SDBS (CAS 25155-30-0), how it is produced from linear alkylbenzene, what the specification numbers actually mean in a powder plant (active matter 80 +/- 2%, bulk density above 0.18 t/m3, moisture below 3%, pH 8.5-11.5 in 1% solution), where it is used beyond laundry, and how to choose between SDBS, LABSA, AOS and SLES for a given formulation.
What Is Sodium Dodecylbenzenesulfonate?
SDBS is an anionic surfactant built from a linear C10-C13 alkyl chain attached to a benzene ring carrying a sulfonate group, neutralised with sodium hydroxide. The commercial product is not one molecule but a distribution of homologues and phenyl isomers, controlled by the linear alkylbenzene feedstock; the “dodecyl” in the name reflects the average chain length rather than a single pure compound.
Two structural features drive everything that follows. The sulfonate head group is fully ionised across the whole practical pH range, which is why SDBS works in strongly alkaline formulations where carboxylate soaps would be protonated and lose surface activity. The linear alkyl tail gives the biodegradability that made LAS the industry standard after branched alkylbenzene (ABS) was phased out in the 1960s.
Chemical Identity: CAS 25155-30-0
| Item | Detail |
|---|---|
| Common names | SDBS, LAS-Na, sodium linear alkylbenzene sulfonate, sodium laurylbenzenesulfonate |
| CAS Registry Number | 25155-30-0 |
| Chemical class | Anionic surfactant; sodium salt of linear alkylbenzene sulfonic acid |
| Alkyl chain | Linear C10-C13, predominantly C12 (homologue mixture) |
| Appearance | White or slightly yellow free-flowing powder / granules |
| Active matter | 80 +/- 2% |
| Bulk density | Min 0.18 t/m3 (approx. 180 g/L) |
| Moisture | Max 3% |
| pH (1% solution, 25 deg C) | 8.5 – 11.5 |
| Related material | LABSA (linear alkylbenzene sulfonic acid, the acid precursor) |
Keep the distinction between SDBS and LABSA sharp in purchasing and in formulation. LABSA is the strong acid, supplied at roughly 96% active matter, and it must be neutralised on site with caustic – a reaction that generates heat and requires dedicated equipment. SDBS arrives neutralised, at 80% active matter in powder form, ready to dry-blend. The two are the same chemistry at different points in the value chain.
How SDBS Is Produced
The chain runs through four steps, and each one leaves a fingerprint in the specification:
- Linear alkylbenzene (LAB). Benzene is alkylated with a linear olefin or chloroparaffin fraction to give a C10-C13 linear alkylbenzene.
- Sulfonation. LAB is sulfonated with sulphur trioxide in a falling-film reactor, producing LABSA at 96%+ active matter.
- Neutralisation. The acid is neutralised with sodium hydroxide solution under controlled temperature and pH. This is where the residual alkalinity in the final product – and therefore the 8.5-11.5 pH window – originates.
- Drying. The neutralised slurry is dried (spray drying, drum drying or a dedicated powder process), milled to the target particle size and classified for bulk density.
The specification numbers map onto those steps: active matter reflects sulfonation and neutralisation efficiency; the 3% moisture limit reflects drying; bulk density reflects particle size distribution; and pH reflects neutralisation endpoint and residual free alkali.
Specifications We Supply
| Property | Specification | What it means in use |
|---|---|---|
| Appearance | White or slightly yellow free-flowing powder / granules | Colour indicates feedstock quality; free-flowing character drives handling |
| Active matter (%) | 80 +/- 2 | Real detergent value; the basis for cost-per-active comparisons |
| Bulk density (t/m3) | Min 0.18 | Lower bulk density means more shipping volume and worse dry-blend behaviour |
| Moisture (%) | Max 3 | Excess moisture causes caking and premature hydrolysis in blended powders |
| pH (1% solution, 25 deg C) | 8.5 – 11.5 | Alkalinity; needs balancing against enzymes, bleach and acidic components |
Three of these five numbers are handling specifications rather than detergent specifications – bulk density, moisture and appearance – and they are the numbers that decide whether a powder plant can actually run your material. A 78% active matter lot with excellent colour but a bulk density of 0.15 t/m3 will cost more in freight and blend segregation than it saves on invoice price.
Key Surface-Active Properties
| Property | Practical significance |
|---|---|
| Anionic, fully ionised sulfonate | Stable and surface active from mildly acidic to strongly alkaline pH – the reason LAS dominates alkaline cleaners |
| Excellent wetting and emulsification of oily soil | Strong on particulate and sebum-type soil in laundry; weaker than nonionics on greasy soil above its cloud point |
| Good foam generation | Desirable in hand-wash and dishwash; a nuisance in machine and industrial systems, where antifoam may be needed |
| Calcium sensitivity | Hard-water performance depends on the builder system: LAS precipitates with Ca2+ unless builders keep calcium in solution |
| Readily biodegradable (linear chain) | The property that displaced branched ABS and keeps LAS acceptable in most markets |
| High solubility in warm water | Dissolves readily; add powder to water with agitation to avoid lumping |
Why Bulk Density and Moisture Matter
In an industrial powder plant, SDBS is one component of a blend that includes builders, alkali, bleach, polymer, enzyme and perfume. Two physical properties decide whether that blend behaves:
- Bulk density above 0.18 t/m3 keeps SDBS in the same density band as zeolite and sodium carbonate. A light, fluffy surfactant segregates in the blender and in the bag, so the consumer gets a dose that varies from wash to wash.
- Moisture below 3% limits the water available for premature reactions in the finished powder – enzyme deactivation, perborate decomposition and caking under load in warm warehouses.
Free-flowing granules also reduce dust in the plant. Dust is both a housekeeping problem and a respiratory exposure issue, and it is the usual reason a plant rejects an otherwise acceptable lot.
Applications
Household detergent powders
SDBS remains the primary anionic surfactant in laundry powder in most markets. A typical formulation pairs it with a builder system (zeolite 4A, sodium carbonate, sodium silicate), a co-surfactant (nonionic alcohol ethoxylate for greasy soil), a polymer (polycarboxylate anti-redeposition), optical brightener, enzyme and perfume.
Industrial and institutional cleaning
Alkaline degreasers, floor cleaners, dairy and brewery cleaning compounds and CIP formulations use SDBS for its stability at high pH and its ability to emulsify fats and oils. In these systems foam control and rinse behaviour matter as much as detergency.
Emulsion polymerisation
SDBS is a standard anionic emulsifier for acrylic, styrene-acrylic, styrene-butadiene and vinyl acetate polymerisations. It provides the ionic stabilisation that keeps latex particles apart, and its particle-size effect is well characterised, which makes it a predictable choice when a formulator needs a narrow particle size distribution.
Agrochemical formulations
Wettable powders and suspension concentrates use SDBS as a wetting and dispersing agent, usually in combination with a nonionic or a naphthalene sulfonate dispersant.
Construction materials
Gypsum board and aerated concrete production use sulfonate surfactants as foaming agents to create the air cells that reduce density. Here the requirement is foam stability in a strongly alkaline, high-solids slurry.
Textile and leather processing
Scouring, wetting and leveling operations use SDBS for its heat and alkali stability, alone or with nonionic co-surfactants.
Formulation Guidance
| Application | Typical SDBS level | Notes |
|---|---|---|
| Laundry powder (household) | 12 – 20% of the finished powder | Balance against nonionic for greasy soil; builder dose set by water hardness |
| Hand dishwash / hand-wash powder | 15 – 25% | Foam is a feature here; pair with a foam booster |
| Alkaline industrial degreaser | 2 – 8% | Combine with nonionic and a hydrotrope for stability at high alkali |
| Emulsion polymerisation | 0.5 – 3% on monomer | Anionic backbone; add nonionic for electrolyte stability |
| Wettable powder (agrochemical) | 2 – 5% | Pair with a dispersant; check suspensibility after ageing |
| Gypsum / aerated concrete foaming | 0.05 – 0.3% on solids | Dilute before injection; foam stability is the controlling property |
These are starting points. The two variables that most often move the answer are water hardness (which changes the builder demand, not the surfactant demand) and the bleach system (perborate or percarbonate plus activator imposes a moisture and alkalinity budget on the whole powder).
SDBS Versus Other Anionic Surfactants
| Surfactant | Form supplied | Hard-water tolerance | Cost per active | Best fit |
|---|---|---|---|---|
| SDBS (LAS-Na) | 80% powder / granule | Moderate – needs builders | Lowest | Powder detergents, alkaline cleaners, emulsion polymerisation |
| LABSA (LAS acid) | 96% acid | Moderate – needs builders | Lowest, but requires on-site neutralisation | Liquid detergents and plants with neutralisation capacity |
| AOS | 92% powder or 34-36% liquid | Good | Higher | Hard water, personal care, enhanced oil recovery |
| SLES | 70% liquid | Good | Higher | Shampoos, liquid detergents, mildness-sensitive products |
| SLS | Powder or needle | Moderate | Higher | Toothpaste, powder with mildness claims |
For a full comparison of the alternatives, including where each one wins on mildness and on electrolyte tolerance, see AOS vs SLES, LAS and SLS.
pH, Compatibility and the Alkalinity Budget
A 1% SDBS solution sits between pH 8.5 and 11.5 – quite a wide window, and the upper end is genuinely alkaline. That matters for three common co-components:
- Enzymes. Proteases and amylases in laundry powders have pH optima around 8-10 and lose activity above that; a lot at the top of the pH window can cost enzyme performance.
- Bleach. Perborate and percarbonate decompose faster at high pH and in the presence of moisture, releasing oxygen before the wash.
- Acidic components. Any acidic builder or pH adjuster will neutralise residual alkali, generate heat and locally liberate free acid, which is both a handling and a stability issue.
The practical control is to ask for the pH of each SDBS lot and to adjust the powder’s alkalinity with sodium carbonate or a mild acid rather than assuming a single value.
Storage, Caking and Tropical Shipping
SDBS is hygroscopic in bulk and slightly alkaline, and both properties matter more in transit than in a warehouse in the country of manufacture. A container that crosses the equator with bags stacked against a steel wall will see temperature swings that drive moisture migration inside the liner – and a powder at the top of the 3% moisture specification has no margin left for that.
| Risk | What happens | Mitigation |
|---|---|---|
| Moisture migration in transit | Surface caking; lumps that will not break down in the blender | Inner PE liner sealed, desiccant where appropriate, pallets away from container walls |
| Compression under stack load | Hard caking at the bottom of the pallet, worse at high warehouse temperature | Limit stack height; use pallets sized for the bag count |
| Prolonged storage above 40 deg C | Colour drift towards yellow; slow loss of free-flowing character | FIFO stock control; shaded storage |
| Humid ambient air during blending | Finished powder picks up moisture from the surfactant, then cakes in the pack | Condition the blending room; blend in dry weather or dehumidified air |
| Acid contact in the warehouse | Liberation of free LAS acid; local corrosion and odour | Segregate from acids and oxidisers |
For tropical destinations the practical answer is a tighter internal moisture specification combined with a properly sealed liner, not a larger desiccant load. Ask for the moisture figure on the actual shipping lot, and check appearance on arrival: a lot that has caked in the container is usually a moisture problem that started before shipment.
Handling, Storage and Safety
SDBS is a mild irritant in concentrated powder form. The controls that matter are dust-related: local exhaust ventilation at weighing and blending, dust masks and eye protection when handling open bags, and prompt clean-up of spills, because a surfactant powder on a wet floor is a slip hazard.
| Item | Practice |
|---|---|
| Storage | Dry, ventilated, on pallets; keep bags sealed to hold moisture below the 3% limit |
| Incompatibility | Strong acids liberate the free acid; keep away from oxidisers in bulk storage |
| Shelf life | Use within the period stated on the COA; caking is the first sign of moisture ingress |
| Spill response | Sweep dry, avoid washing into drains in quantity, prevent foam generation in surface water |
Packaging, Supply and Documentation
| Item | Detail |
|---|---|
| Standard pack | 25 kg net multi-layer bag with inner PE liner |
| Bulk pack | 500-1000 kg jumbo bag on request |
| Palletisation | Shrink-wrapped export pallets; bag count per pallet confirmed per order |
| Documents | COA per batch (appearance, active matter, bulk density, moisture, pH), SDS in English, packing list and shipping documents |
| Samples | Available for blending and polymerisation trials |
Frequently Asked Questions
What is the difference between SDBS and LAS? LAS is the surfactant family and usually refers to the acid (LABSA); SDBS is specifically the neutralised sodium salt, normally supplied as an 80% powder.
Why is the active matter only 80%? The balance is sodium sulfate, sodium chloride, unsulfonated matter and moisture – the natural outcome of neutralising and drying the acid. Higher active grades exist but are harder to dry and to handle.
Can SDBS replace LABSA in my liquid detergent? Chemically yes, practically it is a different process: powders are dry-blended, liquids are normally made by neutralising LABSA in situ. Compare total cost including neutralisation equipment and energy.
Is SDBS suitable for hard water? SDBS works in hard water only with an adequate builder system; if hardness is high and builders are limited, AOS or a nonionic-rich system performs better.
Is SDBS biodegradable? Yes – the linear alkyl chain makes LAS readily biodegradable under standard test conditions, which is why it replaced branched ABS.
Contact PolyBlueChem for specifications, samples, COA and quotations.