Sodium Naphthalene Formaldehyde (SNF)
Sodium naphthalene formaldehyde (SNF), also called PNS, NSF or sodium naphthalene sulfonate formaldehyde condensate (CAS 36290-04-7), is an anionic superplasticizer and dispersant. It is used mainly as a high-range water reducer in concrete, and also as a dispersant in dyes, leather tanning, rubber, paint and oil-well cementing. The grades are distinguished mainly by their sodium sulphate content.
- CAS No.
- 36290-04-7
- Also called
- PNS; NSF; sodium naphthalene sulfonate formaldehyde condensate
- Ion type
- Anionic
- HS code
- 38244010.00
- Grades
- Na2SO4 < 3%, < 5%, 10% max, < 18%, 20% max
SNF Grades Compared
| Grade | Na2SO4 | Net paste fluidity | Chloride | Solids | pH |
|---|---|---|---|---|---|
| SNF 3% (GAC-SNF-3) | < 3% | ≥ 220 mm | < 0.4% | ≥ 91% | 7–9 |
| SNF 5% (GAC-SNF-5) | < 5% | ≥ 220 mm | < 0.4% | ≥ 91% | 7–9 |
| SNF powder, high solids (GAC-SNF-P) | 10% max | — | < 200 ppm | 95% min | 6.5–8.5 |
| SNF 18% (GAC-SNF-18) | < 18% | ≥ 210 mm | < 0.5% | ≥ 91% | 7–9 |
| SNF 20% (GAC-SNF-20) | 20% max | ≥ 210 mm | 0.5% max | 91% min | 7–9 |
Typical values from the current TDS of each grade. Surface tension (71 ± 1) × 10⁻³ N/m for the 3%, 5%, 18% and 20% grades. Batch results are stated on the COA.
Why Sodium Sulphate Content Matters
- Sodium sulphate is a by-product of neutralization. Low-sulphate grades (3%, 5%) carry more active condensate per kilogram and give slightly higher fluidity.
- Low-sulphate grades are preferred for liquid admixtures: at high sulphate levels, sodium sulphate can crystallize out of concentrated solutions in cold weather.
- High-sulphate grades (18%, 20%) are the economical choice for powder use and for dry-mix products.
How SNF Works in Concrete
SNF molecules adsorb on cement particles and give them a strong negative charge, so the particles repel each other and release the water trapped between them. This allows high-range water reduction: much less water for the same workability, or much higher flow at the same water content. Unlike lignosulfonates, SNF adds little set retardation or air entrainment, which is why it is used for high-strength and precast concrete.
Dosage and Use
- Typical dosage: 0.5–1.0% by weight of cementitious material, with 0.75% as a starting point (TDS for the 18% and 20% grades).
- Added as powder or as a solution in the mixing water.
- Check compatibility with the cement and other admixtures in trial mixes; slump loss over time can be faster than with polycarboxylates.
Other Uses
- Dispersant for disperse and vat dyes, pigments and fillers.
- Leather tanning auxiliary.
- Water reducer for oil-well cement.
- Dispersant in rubber latex, paint and gypsum.
Packaging and Storage
- 25 kg woven bags; 650 kg or 700 kg bulk bags for some grades.
- Store in a dry, ventilated warehouse. If the powder takes up moisture, it can still be dissolved and used without loss of effect.
Frequently Asked Questions
What is the difference between SNF grades?
Mainly the sodium sulphate content: under 3%, under 5%, 10% max (high-solids powder), under 18% and 20% max. Lower sulphate means more active material and better suitability for liquid admixtures.
Is SNF the same as PNS and NSF?
Yes. SNF, PNS and NSF are different names for sodium naphthalene sulfonate formaldehyde condensate.
SNF: Product Page, Documents and Quotes
SNF on LigninCorp: grades, documents and quotes.
Related: SNF 20% grade, Dispersant NNO, sodium lignosulfonate construction grade.
Questions about a specification, a test result or a formulation: contact us or email info@greenagrochem.com.