Sodium naphthalene sulphonate formaldehyde (SNF, also spelled sulfonate; also called PNS or NSF) is the sodium salt of a naphthalene sulfonic acid–formaldehyde condensate. It is a brown, water-soluble powder used mainly as a high-range water reducer for concrete and as a dispersant. Our superplasticizer grades are supplied under CAS 36290-04-7.
How It Is Made
Naphthalene is sulfonated with sulfuric acid, condensed with formaldehyde, and neutralised with sodium hydroxide. Neutralisation of the excess acid leaves sodium sulfate in the product; how much is left decides the grade.
Specification by Grade
| Grade | Sodium sulfate (Na2SO4) | Chloride (Cl–) | Cement paste fluidity | Solids | pH |
|---|---|---|---|---|---|
| SNF-5 (GAC-SNF-5) | 5% max | 0.4% max | 220 mm min | 91% min | 7 – 9 |
| SNF-10 (GAC-SNF-10) | 10% max | 0.4% max | 220 mm min | 91% min | 7 – 9 |
| SNF-18 (GAC-SNF-18) | 18% max | 0.5% max | 210 mm min | 91% min | 7 – 9 |
| SNF-20 (GAC-SNF-20) | 20% max | 0.5% max | 210 mm min | 91% min | 7 – 9 |
| Powder Grade, high solids (GAC-SNF-P) | 10% max | Below 200 ppm | Not listed | 95% min | 6.5 – 8.5 (1:10) |
Water Reduction Efficiency
Water reduction is measured in concrete at equal slump against a reference mix without admixture. In the SNF-5 TDS test the result was 17% against a 14% minimum criterion, with air content 2.0% (3.0% max). To be sold as a high-range water reducer, a finished admixture is tested against a reference concrete: ASTM C494 Type F requires mixing water of 88% of the reference or less (at least 12% reduction), and EN 934-2 Table 3.1 requires at least 12% water reduction.
How It Works
The molecules adsorb on cement grains and give them a negative charge, so the grains repel each other and release trapped water. The effect fades as hydration proceeds, which is why concrete with SNF loses slump over time.
Uses
- Concrete, precast and dry-mix mortar: high-range water reducer.
- Oil-well cement slurries: dispersant.
- Dyes and pigments: dispersant, usually sold as Dispersant NNO (NNO product page).
- Gypsum and other mineral slurries: dispersant.
Dose
The current TDS gives a supplier-recommended starting trial range of 0.5–1.0% powder by weight of cementitious material, with 0.75% as the first trial point. Confirm the working dose by trial mixes with your own cement, aggregates and admixtures.
Grades, samples and quotations: SNF product page.
Frequently Asked Questions
What is sodium naphthalene sulphonate formaldehyde?
A naphthalene sulfonic acid–formaldehyde condensate in sodium salt form (SNF, PNS, NSF), used as a concrete superplasticizer and dispersant.
What is the water reduction of sodium naphthalene sulphonate formaldehyde?
In the SNF-5 TDS concrete test it was 17% (criterion 14% min). Results in your mix depend on the cement, aggregates and dose.
Why is there sodium sulfate in SNF?
It forms when the excess sulfuric acid is neutralised with sodium hydroxide. Grades are named by the maximum sodium sulfate content.
Is it sulphonate or sulfonate?
Both spellings are used; “sulphonate” is British and “sulfonate” American. They name the same product.
