NSF (naphthalene sulfonate formaldehyde) is the sodium salt of a naphthalene sulfonic acid–formaldehyde condensate. It is the same material sold as SNF, PNS or Dispersant NNO. It is a water-soluble anionic polymer used as a high-range water reducer in concrete and as a dispersant for dyes, pigments, gypsum and pesticides.
Names and Identity
| Item | Detail |
|---|---|
| Names | NSF, SNF, PNS (polynaphthalene sulfonate), sodium naphthalene formaldehyde, Dispersant NNO |
| CAS No. | 36290-04-7 (on our SNF TDS); 9084-06-4 is also widely used |
| HS code | 3824401000 (SNF TDS) |
| Form | Brown to dark brown powder (SNF); yellow-brown to light yellow powder (NNO) |
| Ionic type | Anionic |
How It Works
The polymer adsorbs on particle surfaces and gives them a negative charge, so the particles repel each other. Water trapped in clusters of cement or pigment is released, and the suspension flows at lower water content. The mechanism is electrostatic; polycarboxylate (PCE) superplasticizers add steric hindrance from side chains. How the condensate is made and what each specification item means: what is naphthalene sulfonate formaldehyde.
Grades
| Grade | Na2SO4 | Cement paste fluidity | Chloride | Solids | pH |
|---|---|---|---|---|---|
| SNF 3% (GAC-SNF-3) | < 3% | ≥ 220 mm | < 0.4% | ≥ 91% | 7 – 9 |
| SNF 5% (GAC-SNF-5) | 5% max | 220 mm min | 0.4% max | 91% min | 7 – 9 |
| SNF 10% (GAC-SNF-10) | 10% max | 220 mm min | 0.4% max | 91% min | 7 – 9 |
| SNF 18% (GAC-SNF-18) | 18% max | 210 mm min | 0.5% max | 91% min | 7 – 9 |
| SNF 20% (GAC-SNF-20) | 20% max | 210 mm min | 0.5% max | 91% min | 7 – 9 |
| SNF powder, high solids (GAC-SNF-P) | 10% max | — | < 200 ppm | 95% min | 6.5 – 8.5 (1:10) |
| Parameter | NNO Grade A | NNO Grade B | NNO Grade C | NNO High-Purity |
|---|---|---|---|---|
| Appearance | Brown powder | Brown powder | Light yellow powder | Powder |
| Dispersing power (vs standard) | 95% min | 90% min | — | — |
| Sodium sulfate | 5% max | 18% max | 22% max | Sulphate about 3.0% |
| pH | 7 – 9 (1%) | 7 – 9 (1%) | 7 – 9 (1%) | 7.0 – 9.0 (2%) |
| Ca + Mg | 0.4% max | 0.4% max | Cl, Ca, Mg 0.15% max | — |
| Water-insoluble matter | 0.05% | 0.05% | 0.1% max | — |
| Other | — | — | Water 8% max; free formaldehyde 200 ppm max | Free naphthalene < 5 ppm; free formaldehyde < 50 ppm; quinoline < 200 ppm |
Applications
| Application | Role | Grade to start with |
|---|---|---|
| Ready-mix and precast concrete | High-range water reducer | SNF 5%, 18% or 20% |
| Gypsum board | Reduces slurry water | SNF or NNO High-Purity |
| Dyes and pigments | Dispersant and diffusing agent | NNO Grade A or C |
| Pesticides (WP, WDG) | Dispersant | NNO |
| Leather | Auxiliary tanning agent | SNF / NNO |
| Oil-well cement | Water reducer | SNF |
Concrete Performance
| Test (concrete) | Criterion | SNF 5% | SNF 18% / 20% |
|---|---|---|---|
| Water reduction | 14% min | 17% | 16% |
| Air content | 3.0% max | 2.0% | 2.0% |
| Water penetration ratio | 90% max | 80% | 85% |
| Compressive strength ratio, 1 d | 140% min | 165% | 160% |
| Compressive strength ratio, 3 d | 130% min | 155% | 155% |
| Compressive strength ratio, 7 d | 125% min | 135% | 135% |
| Compressive strength ratio, 28 d | 120% min | 130% | 125% |
| Shrinkage ratio, 28 d | 135% max | 87% | 89% |
Supplier-recommended starting trial range for SNF in concrete: 0.5 – 1.0% by weight of cementitious material, with 0.75% as a first trial level (grade TDS). Confirm the dose in trial mixes with your own cement and aggregates.
NSF, Lignosulfonate or PCE?
NSF gives higher water reduction than lignosulfonate with less set retardation; PCE reaches higher water reduction at lower dosage and holds slump longer but is more sensitive to cement and clay. Many plants blend NSF with lignosulfonate. Compare in trial mixes: PCE superplasticizer and sodium lignosulfonate.
Checks on Receipt
- Compare the COA with the TDS for each listed item.
- Check appearance and that the bags or containers are sealed and dry.
- Make a 1% solution in water and look for undissolved matter.
- Measure pH of the solution and compare with the TDS range.
- Keep a retained sample of each batch for later comparison.
Products: SNF product family, Dispersant NNO. Grade selection guide: SNF superplasticizer guide.
Frequently Asked Questions
What is NSF in concrete?
Naphthalene sulfonate formaldehyde condensate, a high-range water reducer (superplasticizer). It is the same material as SNF or PNS.
Is NSF the same as SNF?
Yes. NSF, SNF and PNS are different names for sodium naphthalene sulfonate formaldehyde condensate.
What is the CAS number of sodium naphthalene sulfonate formaldehyde condensate?
36290-04-7 is given on our SNF TDS; 9084-06-4 is also widely used.
Does NSF entrain air?
Air content in the TDS concrete test was 2.0%, within the 3.0% maximum criterion.
