Sulfonated melamine formaldehyde (SMF) is a synthetic anionic polymer made by condensing melamine with formaldehyde and sulfonating the product. In construction it is used as a high-range water reducer (superplasticizer) for concrete, mortars and gypsum, alongside sodium naphthalene formaldehyde (SNF) and polycarboxylate ether (PCE). Its best-known practical advantage is colour: SMF solutions are nearly colourless. That makes it a common choice for white cement, decorative concrete and light-coloured gypsum products, where brown lignosulfonate or naphthalene admixtures can tint the surface.
How SMF works
The sulfonate groups adsorb on cement or gypsum particles and give them a negative surface charge. The particles repel each other, release trapped water and the mix becomes more fluid at the same water content, or reaches the same flow with less water. Like SNF, SMF acts mainly by electrostatic repulsion. PCE adds strong steric repulsion through its side chains.
Standard performance class
| Standard | Class SMF is normally tested against | Minimum water reduction vs control |
|---|---|---|
| ASTM C494 | Type F (high-range water reducing) or Type G (high-range, retarding) | ≥12% |
| EN 934-2 | High-range water reducing / superplasticizing admixture | ≥12% |
These are class minimums in a reference concrete. Actual water reduction, slump retention and strength depend on the grade, dosage, cement and aggregates.
SMF compared with SNF and PCE
| Property | SMF | SNF | PCE |
|---|---|---|---|
| Main mechanism | Electrostatic | Electrostatic | Steric plus electrostatic |
| Colour | Nearly colourless | Brown | Light |
| Set retardation | Low | Low | Formulation-dependent |
| Slump retention | Limited; often dosed late or combined | Limited | Can be designed for long retention |
| Typical niches | White and decorative concrete, gypsum, self-levelling and precast | General high-range water reduction, precast | High-performance and self-compacting concrete |
Grade qualification
- Confirm the chemistry: SMF (melamine) is not Dispersant MF, which is a methylnaphthalene sulfonate condensate used mainly in dyes. See Dispersant MF.
- Request the solids, pH, chloride and sulphate content, plus free formaldehyde, from the current TDS and SDS.
- Run a trial mix: water reduction at equal slump, slump loss over time, setting time, air content, and 1-, 7- and 28-day strength against a control and your current admixture.
- For white or decorative work, check surface colour and efflorescence on test panels.
- For gypsum and self-levelling compounds, measure flow, setting and strength with the actual binder.
Handling and compliance
SMF is made with formaldehyde, so residual free formaldehyde depends on the manufacturing process and grade. Follow the SDS for the exact grade and confirm destination-market requirements, such as formaldehyde classification and labelling, before use.
Related construction admixtures
SNF superplasticizer · PCE powder · lignosulfonate concrete admixture · HPMC for mortars. For SMF availability, TDS and samples, contact info@greenagrochem.com.
