Question 1

Why is GMATT UV specified for 100% solids UV systems rather than standard wax-treated grades?

Accepted Answer

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).

Question 2

How does GMATT UV affect viscosity in 100% solids UV-curable wood clear coat?

Accepted Answer

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.

Question 3

How does GMATT UV refractive index optimisation affect UV through-cure depth?

Accepted Answer

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.

Question 4

Can GMATT UV be used in UV-inkjet inks for digital printing?

Accepted Answer

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.

Question 5

Does GMATT UV prevent blocking in UV lamination coatings?

Accepted Answer

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.

السيناريو	الدرجة الموصى بها	DFT المستهدف	الإضافة
طلاء أرضيات خشب UV شفاف، مطفأ	GMATT UV	15–30 µm	3.0–5.0 wt%
تشطيب تجهيزات بلاستيك UV	GMATT UV	10–20 µm	2.5–4.5 wt%
تشطيب حبر UV مطفأ	GMATT UV	3–8 µm	2.0–4.0 wt%
مقاومة التصاق تصفيح UV	GMATT UV	5–15 µm	3.0–5.0 wt%
تشطيب ألواح خشب EB	GMATT UV	20–40 µm	3.0–5.0 wt%

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