Non-Wax Surface Design for 100% Solids UV Systems
UV-curable coatings are 100% solids systems — no water, no solvent — composed entirely of reactive monomers, oligomers, photoinitiators, and additives. Introducing a wax-treated silica into this environment creates incompatibility risks: the wax can interfere with acrylate oligomer network formation at the curing interface, causing haze or surface defects in clear UV coatings. GMATT UV is engineered with a non-wax, low-oil-absorption surface modification specifically designed for compatibility with the reactive environment of UV-curable systems. At 3.0–5.0 wt% in UV wood clear coat, UV plastic topcoat, and UV inkjet applications, GMATT UV provides matte appearance (60° gloss 10–30 GU) without surface defects or compatibility-driven yellowing.
Minimal Viscosity Impact in Reactive Oligomer Blends
Application viscosity is critical in UV-curable coatings: too high and the coating cannot be applied at production line speed; too low and the film sags before cure. GMATT UV's low oil absorption (significantly lower than standard precipitated silica grades) ensures that fewer reactive monomer molecules are adsorbed into the silica pore structure, preserving the free monomer/oligomer concentration that controls application viscosity. At 3.0–5.0 wt% in a typical 100% solids UV wood clear coat (base viscosity 400–600 mPas at 25°C), GMATT UV adds only 20–40 mPas — maintaining application stability at line speeds up to 30 m/min without heating the applicator.
Refractive Index Optimisation for Rapid Through-Cure
In UV clear coats, silica particles scatter UV radiation from the mercury or LED cure source, reducing the photon flux at depth and creating undercure risk at the film/substrate interface. GMATT UV is manufactured with a refractive index closely matched to typical acrylate oligomer/monomer blends (n ≈ 1.48–1.50), minimising internal UV scattering. This transparency to UV radiation ensures the photoinitiator at depth receives sufficient photon energy for complete crosslinking in a single UV pass — critical for UV wood floor coating lines running at 20–35 m/min under standard medium-pressure mercury or LED UV sources.
Anti-Blocking in UV Lamination and Flexible Packaging
UV-cured matte finishes on paper, board, and flexible packaging substrates are susceptible to blocking — the sticking of coated surfaces under warehouse stack pressure. GMATT UV at 3.0–5.0 wt% in UV lamination topcoat creates a controlled micro-textured surface that prevents inter-surface adhesion under typical stack loads (3–5 kPa), without requiring migratable wax or PTFE anti-blocking additives that are incompatible with food contact or recycling standards.
When to Use GMATT UV for UV-Curable Coatings
GMATT UV's non-wax, low-oil-absorption, RI-matched profile makes it the essential choice for any 100% solids UV-curable system where viscosity control, through-cure integrity, and surface compatibility are design constraints.
| Scenario | Recommended Grade | Target DFT | Loading |
|---|---|---|---|
| UV wood floor clear coat, matte | GMATT UV | 15–30 µm | 3.0–5.0 wt% |
| UV plastic trim topcoat | GMATT UV | 10–20 µm | 2.5–4.5 wt% |
| UV inkjet matte topcoat | GMATT UV | 3–8 µm | 2.0–4.0 wt% |
| UV lamination anti-blocking | GMATT UV | 5–15 µm | 3.0–5.0 wt% |
| EB-curable wood panel topcoat | GMATT UV | 20–40 µm | 3.0–5.0 wt% |
Technical FAQ
GMATT UV formulation specifics for 100% solids UV-curable wood, plastic, ink, and lamination applications.
+Why is GMATT UV specified for 100% solids UV systems rather than standard wax-treated grades?
Standard wax-treated silica grades (e.g., GMATT 200 Series) are optimised for solventborne or waterborne systems where their wax surface treatment provides anti-settling and anti-caking benefits. In 100% solids UV-curable systems — which contain no solvent and no water — the wax surface treatment is unnecessary and can interfere with the acrylate oligomer network by creating incompatibility points. GMATT UV uses a non-wax surface modification with low oil absorption that minimises viscosity increase in reactive diluent and oligomer blends, enabling stable formulation viscosity through the pot life and across the application temperature range (20–40°C).
+How does GMATT UV affect viscosity in 100% solids UV-curable wood clear coat?
In 100% solids UV clear coat (typical viscosity 300–800 mPas at 25°C), GMATT UV at 3.0–5.0 wt% causes a viscosity increase of 20–40 mPas — significantly lower than equivalent loadings of high-oil-absorption precipitated silica grades (which can add 100–200 mPas). The low oil absorption of GMATT UV means fewer binder components are adsorbed by the silica pore structure, preserving the free oligomer concentration that controls application viscosity. This allows UV line speeds up to 30 m/min without viscosity-related application defects.
+How does GMATT UV refractive index optimisation affect UV through-cure depth?
In UV-curable systems, silica particles scatter UV radiation, reducing the photon flux reaching the photoinitiator at depth in the film. GMATT UV is manufactured with a refractive index closely matched to the weighted mean refractive index of typical acrylate oligomer/monomer blends (n ≈ 1.48–1.50), minimising UV scattering within the coating film. This improves through-cure efficiency — critical for UV matting on wood substrates where the topcoat must cure fully from surface to substrate interface in a single UV pass.
+Can GMATT UV be used in UV-inkjet inks for digital printing?
GMATT UV is compatible with UV-curable inkjet inks formulated with acrylate monomers and oligomers, provided the particle size is verified against the inkjet head nozzle diameter. For standard industrial inkjet heads (nozzle diameter 50–100 µm), GMATT UV with d99 below 20 µm is suitable for matte topcoat inkjet inks applied at 2.0–4.0 µm DFT. In functional inkjet (primer and topcoat in a single pass), GMATT UV's low viscosity impact preserves the narrow jetting viscosity window (8–12 mPas at 35°C) required for reliable drop formation.
+Does GMATT UV prevent blocking in UV lamination coatings?
Yes. Blocking — the sticking of coated surfaces when stacked under pressure — is a known defect in UV-cured matt finishes on paper, film, and flexible packaging. GMATT UV at 3.0–5.0 wt% in UV lamination topcoat creates a micro-textured surface with sufficient roughness to prevent inter-surface contact under typical warehouse stack loads (up to 5 kPa). The anti-blocking benefit is provided by the silica particle protrusion mechanism and does not require additives that could migrate and contaminate food packaging applications.
Recommended Solution
For 100% solids UV-curable wood, plastic, ink, and lamination coatings where viscosity stability, UV through-cure, and anti-blocking performance are required, specify GMATT UV Series — non-wax, RI-matched silica engineered for reactive UV environments.
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