A detergent powder is not a bag of surfactant; it is a blend of surfactant, builder, alkali, bleach, polymer and enzyme that has to survive blending, packing, storage and a wash cycle without any of those components destroying the others. SDBS (CAS 25155-30-0) is the anionic surfactant at the centre of that blend, and the way it is specified – active matter, bulk density, moisture, pH – determines whether the powder works in a plant and in a washing machine.
This guide is written for formulators and plant engineers: how SDBS behaves in a powder, how much to use, how it interacts with builders and bleach, what goes wrong in industrial cleaning compounds, and which tests catch a problem before the customer does.
Why powder plants buy SDBS rather than LABSA
Both are the same chemistry. The difference is where the neutralisation happens. LABSA is a 96% acid that must be neutralised with caustic on site, producing heat, requiring a dedicated neutralisation vessel, and generating a slurry that then has to be dried. SDBS arrives already neutralised, at 80 +/- 2% active matter in powder form, and can be dry-blended directly with builders.
| Factor | SDBS 80% powder | LABSA 96% acid |
|---|---|---|
| Capital equipment | Blender only | Sulfonation/neutralisation plant plus drying |
| Handling hazard | Dust irritant | Strong acid; corrosive, exothermic neutralisation |
| Flexibility | Fixed 80% active | Any active level by dilution |
| Cost per unit active | Higher (you ship 20% inactive) | Lower, if you already own the plant |
| Best fit | Powder detergents, industrial blends | Liquid detergents, integrated surfactant producers |
The four numbers that decide plant performance
Active matter 80 +/- 2%
Active matter is the detergent value. Everything else in the bag – sodium sulfate, sodium chloride, unsulfonated matter, water – is carried at freight cost and takes space in the blender. This is why serious buyers compare quotations on cost per unit of active matter, and why a “cheap” 76% lot is usually not cheap.
Bulk density above 0.18 t/m3
Blend segregation is the silent killer of powder quality. Zeolite 4A, sodium carbonate and sodium sulfate all sit in a relatively narrow density band; if the surfactant is much lighter, it separates during conveying and settling, and the last bag off the pallet washes differently from the first. A bulk density above 0.18 t/m3 keeps SDBS in that band.
Moisture below 3%
Water is the enemy of every other component in a laundry powder: it deactivates enzymes, decomposes percarbonate, promotes caking and corrodes packaging. The surfactant is a major moisture carrier if it is over-dried insufficiently, so the 3% limit is really a stability budget for the whole formula.
pH 8.5-11.5 in 1% solution
The alkalinity carried through neutralisation is a formulation input, not a defect. In an alkaline laundry powder it is welcome; in a formula with enzymes or a bleach activator it has to be offset with a mild acid or a lower-alkalinity surfactant lot.
Building the rest of the powder around it
| Component | Typical level (%) | Function | Interaction with SDBS |
|---|---|---|---|
| SDBS | 12 – 20 | Primary anionic surfactant | – |
| Nonionic (alcohol ethoxylate) | 2 – 6 | Greasy soil, low-foam in machines | Reduces total foam, improves oily soil removal |
| Zeolite 4A | 15 – 25 | Calcium sequestration (builder) | Essential – protects SDBS from hard water |
| Sodium carbonate | 10 – 20 | Alkalinity, saponification | Raises pH; watch enzyme compatibility |
| Sodium silicate | 2 – 6 | Corrosion inhibition, anti-redeposition | Also a builder; improves particle strength |
| Polycarboxylate | 1 – 3 | Anti-redeposition, scale control | Complements SDBS on particulate soil |
| Sodium percarbonate / perborate | 10 – 20 | Bleach | Moisture and pH sensitive; coat or separate |
| Enzyme | 0.3 – 1 | Protein/starch soil | pH and moisture sensitive; consider separate granule |
| Optical brightener, perfume | 0.1 – 0.5 | Consumer perception | Neutral |
Industrial and institutional cleaning
In industrial cleaning SDBS is used for a different reason: sulfonates stay surface-active in strongly alkaline conditions, where soap-based surfactants would be protonated and lost. Typical formulations include:
- Alkaline degreasers (2-8% SDBS with sodium hydroxide, a nonionic and a hydrotrope such as sodium xylene sulfonate).
- Dairy and brewery CIP, where foam behaviour and rinse-out matter as much as cleaning power; a low-foam nonionic is usually blended in.
- Floor and hard-surface cleaners, where SDBS provides detergency and the builder provides alkalinity without damaging the substrate.
Two practical traps: foam in high-pressure or circulation systems (add an antifoam, do not just cut the surfactant, or cleaning performance falls with it) and hard-water dilution, which consumes anionic surfactant unless a chelant is present.
What goes wrong, and how to test for it
| Symptom | Likely cause | Test |
|---|---|---|
| Caking in the bag | Moisture above limit, or hygroscopic builder absorbing water | Moisture on incoming lots; accelerated storage at 40 deg C / 80% RH |
| Varying wash performance between bags | Blend segregation from density mismatch | Sample top, middle and bottom of each bag for active matter |
| Poor cleaning in hard water | Insufficient builder; SDBS neutralised by calcium | Wash tests at the actual water hardness; check zeolite/carbonate level |
| Loss of enzyme performance | pH at the top of the SDBS window | pH of 1% solution per lot; check powder pH after blending |
| Bleach smell or loss of whitening | Percarbonate decomposition from moisture plus alkalinity | Available oxygen on stored samples |
| Excess foam in machines | Surfactant level too high for the wash system | Foam height test; rebalance with nonionic and antifoam |
Frequently asked questions
How much SDBS goes into a laundry powder? Typically 12-20% of the finished powder as the primary anionic, with a nonionic at 2-6% for greasy soil. Builder level, not surfactant level, should be adjusted for water hardness.
Can I use SDBS in a liquid detergent? It dissolves, but the powder grade is designed for dry blending. Liquids are usually made by neutralising LABSA in situ or from a 30% SDBS slurry.
Does SDBS work in cold-water washes? Yes, but its performance at low temperature benefits from a co-surfactant and from a polymer that keeps soil suspended; consider raising the nonionic share for cold-wash claims.
Is the pH range a problem for enzymes? Potentially. Ask for lot-specific pH and keep the finished powder within the enzyme’s optimum – or granulate the enzyme separately.
Contact PolyBlueChem for SDBS samples, COA and formulation support.