Thin Film Coatings: Why Particle Size Must Stay Below 8 μm
In coatings under 25 μm dry film thickness (DFT), matting agent particles must be small enough to protrude from the surface without compromising film integrity. A D50 of 3–6 μm is the standard spec window — particles above 8 μm will breach the film surface unevenly, causing visible texture defects and reduced scratch resistance. GMATT 100 Series grades with D50 around 4.5 μm deliver 15–25 gloss units (GU) at 60° with only 3–5% loading by weight. The cost efficiency is notable: smaller particles require less total loading to hit target gloss in thin films, keeping raw material spend per square meter competitive.
Thick Build Coatings: Scale Loading, Not Just Particle Size
Coatings above 100 μm DFT demand a fundamentally different approach. Larger particles (D50 8–15 μm) are required because fine particles simply get buried in the film matrix and never reach the surface to scatter light. GMATT 300 Series grades, with D50 values in the 10–12 μm range, are purpose-built for these applications. Loading rates climb to 5–8% by weight, and in some industrial protective coatings above 150 μm, formulators push to 10%. The trade-off is clear: material cost per batch rises, but gloss reduction per percentage point of loading is far more efficient than forcing fine-particle grades into thick films.
The 25–100 μm Mid-Range: Blending for Precision
Mid-range DFT coatings between 25 and 100 μm sit in a challenging zone where neither pure fine-particle nor pure coarse-particle grades perform optimally alone. Experienced formulators blend two grades — typically a 4–6 μm D50 grade at 2–3% with an 8–12 μm D50 grade at 2–4% — to create a bimodal particle distribution that mats both the surface micro-roughness and the deeper film structure. This approach achieves 20–35 GU at 60° with better surface feel than either grade alone. The particle size distribution of your matting agent matters as much as the median — narrow-cut grades give more predictable blending results.
Cost Analysis: Price Per Gloss Unit Drops in Thick Films
Buyers sourcing matting agents should evaluate cost not per kilogram but per gloss unit reduced per square meter. In thin films (≤25 μm), fine-particle grades like GMATT 100 Series typically cost 15–20% more per kg than coarse grades, but achieve target gloss at lower loading — net cost difference narrows to under 5%. In thick builds (>100 μm), coarse-particle GMATT 300 Series grades deliver 2–3× more gloss reduction per percentage point of loading versus fine grades, making them 30–40% cheaper on a per-gloss-unit basis. Current Q2 2026 pricing shows precipitated silica matting agents holding steady at $2,800–3,400/MT FOB China, with gel-type grades commanding a $400–600 premium.
Quick-Reference: Film Thickness vs Matting Agent Specs
The table below summarizes recommended particle size, loading, and expected gloss performance across three DFT ranges. Use it as a starting point — actual results vary with resin system, application method, and curing conditions.
| DFT Range | Recommended D50 | Loading (wt%) | Expected 60° Gloss | Suggested Grade |
|---|---|---|---|---|
| ≤25 μm | 3–6 μm | 3–5% | 15–25 GU | GMATT 100 Series |
| 25–100 μm | Blend 4–6 + 8–12 μm | 4–7% | 20–35 GU | GMATT 100 + 300 blend |
| 100–200 μm | 8–12 μm | 5–8% | 25–40 GU | GMATT 300 Series |
| >200 μm | 10–15 μm | 8–12% | 30–50 GU | GMATT 300 Series |
Frequently Asked Questions
Common questions about selection guide.
+What particle size matting agent should I use for thin film coatings under 25 μm?
Use a matting agent with D50 of 3–6 μm for coatings under 25 μm DFT. Particles larger than 8 μm will protrude unevenly from thin films, causing surface defects and reduced mechanical performance. GMATT 100 Series grades at 3–5% loading typically achieve 15–25 GU at 60°.
+Why do thick build coatings need larger matting agent particles?
Fine particles get buried within thick film matrices and never reach the surface to create light-scattering micro-roughness. Coatings above 100 μm DFT require D50 values of 8–15 μm so particles can protrude at the air-film interface. Without adequate particle size, you waste loading without reducing gloss.
+Can I use the same matting agent for both thin and thick coatings?
Not effectively. A single D50 grade compromises performance in at least one thickness range. Fine grades waste loading in thick films; coarse grades cause defects in thin films. For mid-range DFT (25–100 μm), blending two grades with different D50 values is the standard industry approach.
+How much matting agent do I need for coatings over 100 μm?
Thick build coatings over 100 μm typically require 5–8% matting agent loading by weight, rising to 8–12% for films above 200 μm. Use coarse-particle grades (D50 8–15 μm) like GMATT 300 Series to maximize gloss reduction efficiency per percentage point of loading.
+What is the current market price for silica matting agents in 2026?
Q2 2026 pricing for precipitated silica matting agents holds at $2,800–3,400/MT FOB China. Gel-type grades carry a $400–600/MT premium over precipitated types. Prices have remained stable through April–May with no significant supply disruptions reported.
+Does matting agent particle size affect surface feel and scratch resistance?
Yes. Finer particles (D50 3–6 μm) produce smoother surface feel and better scratch resistance in thin films. Coarser particles (D50 >10 μm) create more pronounced texture but may reduce pencil hardness by 1–2 grades. Particle size distribution width also affects feel — narrow-cut grades give silkier surfaces.
Match particle size to film thickness first, then optimize loading. Fine particles (D50 ≤6 μm) for thin films under 25 μm; coarse particles (D50 8–15 μm) for thick builds over 100 μm; blend both for mid-range DFT.