The procurement question
You're formulating a heavy-duty industrial coating — marine protective, bridge and infrastructure, refinery equipment, water-treatment plant. The sheen needs to be matt (15-25 GU) for visibility-safety reasons (less glare reflecting off equipment). Plus, the high-build film (200-400 μm dry) needs anti-sag during application + anti-settling during storage.
These two functions — matting and anti-settling — historically came from separate additives. East Materials' approach: HMMAT 700 series (matting) + HJSIL 300 (anti-settling) combination that delivers both in a single coating formulation, with better performance than either alone.
Why heavy-duty industrial differs from architectural
Architectural matt paint (interior walls, exterior facade) is single-coat, 80-150 μm dry film, application at 23°C. Industrial maintenance coating is:
- High-build (200-400 μm dry per coat, often multi-coat to total 1-2 mm)
- High-pressure airless spray (3000+ psi gun, 0.025-0.035 inch tip)
- Service temperature (-30°C to +180°C)
- Chemical resistance (acid, alkali, solvent splash)
- Salt-spray and humidity (marine, infrastructure, water treatment)
The procurement problem: a matting silica that works in 100 μm interior paint may fail at 300 μm industrial coating because the silica particles settle in the wet film before drying. You need both rheology (yield stress holding paint vertical during application) AND matting (final film optical property).
The dual-additive approach
HMMAT 700 series — wax-treated matting silica with high oil absorption
| Property | HMMAT 700 |
|---|---|
| Particle size (D50) | 7-10 μm |
| Internal porosity | High (300+ ml/100g oil absorption) |
| Surface treatment | Wax-treated |
| BET surface area | 350-450 m²/g |
| Sheen at 4% loading in 200 μm film | 15-25 GU at 60° |
The high oil absorption (300+) means HMMAT 700 contributes to coating viscosity not just to surface roughness. At 4-7% loading on resin solids, it provides:
- Sheen target (15-25 GU)
- Initial yield stress (anti-sag during application)
- Anti-settling during shelf storage
HJSIL 300 — high-BET fumed silica for premium rheology
| Property | HJSIL 300 |
|---|---|
| BET surface area | 300 ± 30 m²/g |
| Tapped density | 50 ± 10 g/L |
| Loss on ignition | <2.0% |
| Reference | Aerosil 300, HDK T30 |
HJSIL 300 at 1.0-2.5% on total formulation provides aggressive yield stress for high-build vertical application — critical for the 200-400 μm dry film.
The combined effect
Used together at 4-7% HMMAT 700 + 1.0-2.0% HJSIL 300, you get:
- Matt sheen (15-25 GU at 60°)
- Pre-shear viscosity > 50,000 cps at 0.1 s⁻¹ (anti-sag at 0° spray)
- Post-shear viscosity 200-500 cps at 100 s⁻¹ (airless spray-friendly)
- Settling rate < 5 mm in 30 days at 25°C
- Service-temperature stability (HJSIL 300 maintains rheology to 80°C+; HMMAT 700 surface is wax-stable to 100°C)
Formulation example — 2K epoxy primer for industrial steel
| Component | % w/w | Role |
|---|---|---|
| Epoxy resin (DGEBA, MW 700, solid) | 35 | Binder |
| Polyamine curing agent | 12 | Hardener (Part B) |
| TiO₂ pigment | 14 | Hiding |
| Zinc phosphate | 8 | Corrosion inhibitor |
| Talc filler | 12 | Bulk filler |
| HMMAT 700 | 5 | Matting + anti-settling |
| HJSIL 300 | 1.5 | High-build anti-sag |
| Xylene + n-butanol | 10 | Solvent |
| Surface additives (wetting, anti-foam) | 2.5 | Application aids |
The 5% HMMAT 700 + 1.5% HJSIL 300 combination is the standard for industrial maintenance coating manufacturers in China, Europe, and increasingly North America. Dry film 200-300 μm; recommended overcoat after 8-48 hours.
When this combination doesn't work
Cold-application (below 5°C application temperature). HMMAT 700's wax surface treatment can transition phase below 5°C, causing surface defects. For cold-application industrial coatings, switch to HMMAT 800 (untreated matting silica) + HJSIL 300 combination.
Anti-corrosion top coat (final exposed surface to salt-spray). The HMMAT 700 + HJSIL 300 combination is for the primer / build-coat layer. The top coat (in a 3-coat system) often needs different rheology — see Anti-Corrosion Coatings Hub.
UV-cure industrial coating. The wax surface treatment of HMMAT 700 can absorb UV at very high loadings (>6%), slowing cure. For UV-cure industrial coating, use HMMAT 100 UV-transparent series instead.
Substituting from competitor combinations
| Existing combination | East Materials equivalent | Notes |
|---|---|---|
| Acematt OK 412 + Aerosil 300 | HMMAT 700 + HJSIL 300 | Direct 1:1 substitution, cost savings 30-40% |
| Sylobloc + Sipernat 320 | HMMAT 700 + HJSIL R274 (hydrophobic) | If solvent-based, hydrophobic R974 preferred |
| Eshunzol + Tixosil 38 | HMMAT 700 + HJSIL 200 | If lower-build paint (<200 μm) |
Procurement notes
HMMAT 700: MOQ 1 pallet (1.0 t), lead time 4-5 weeks FOB Shanghai. HJSIL 300: MOQ 1 pallet (1.2 t), lead time 4-5 weeks FOB Shanghai.
For combined supply, both grades can ship in a single container with cost optimization.
FAQ
Why not use just HJSIL 300 alone? It also has high BET.
Fumed silica gives rheology but not matting. The particle size of fumed silica aggregates (100-500 nm) is below the wavelength of light, so they don't scatter visible light — coatings remain glossy even at 5% HJSIL 300. You need matting silica (4-12 μm particles) for the sheen reduction.
What about cost? HMMAT 700 is more expensive than 600.
HMMAT 700 is ~10-15% more expensive than HMMAT 600 due to the higher internal porosity manufacturing. For industrial coating manufacturers, the cost premium is justified by: (1) anti-settling function reduces formulation re-stirring requirements; (2) high-build performance reduces inspector-rejection rate; (3) shelf-life is longer due to better settling resistance. Total cost of ownership is typically lower.
Are these grades food-contact compliant?
HJSIL 300 (hydrophilic) — yes, FDA 21 CFR 175.300 indirect food contact. HMMAT 700 (matting, wax-treated) — for cosmetic/leather use only, not food contact. For food-contact industrial coatings (food processing equipment), use HMMAT 600 (un-waxed or natural-wax versions) + HJSIL R274 instead.
Related
- HMMAT® Matting Agents Hub — full 6-series lineup
- HJSIL® Fumed Silica Hub — 8 grades for rheology selection
- How to Choose Matting Agent for Wood Coatings — companion application
- Anti-Corrosion Coatings Hub — for top-coat additives
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