Name: Stearic-Coated CaCO3 for Sealant Processing SCS-3
Brand: Coatingsink
SKU: calcium-carbonate-stearic-coated
Availability: InStock

Question 1

Why choose stearic-acid-coated CaCO3 over uncoated ground calcium carbonate in sealants?

Accepted Answer

The stearic acid surface treatment renders SCS-3 organophilic, improving polymer-filler compatibility in silicone, PU, and MS sealant matrices. Compared to uncoated grades at the same D50, SCS-3 reduces mix viscosity by 20–30%, suppresses moisture uptake, and prevents agglomeration during storage, yielding more consistent extrusion behaviour and sag resistance.

Question 2

At what dosage is SCS-3 used in neutral-cure silicone sealants?

Accepted Answer

Loadings of 30–60 phr are typical. At 40–50 phr, SCS-3 builds the thixotropic structure needed for non-sag performance while maintaining elongation at break >200%. Loadings above 60 phr reduce raw-material cost further but can begin to reduce elongation and may impact UV weatherability in exposed glazing or façade applications.

Question 3

Does SCS-3 consume NCO groups or cause foaming in moisture-cure polyurethane sealants?

Accepted Answer

No. The stearic coating and low moisture content (≤0.3%) make SCS-3 chemically inert toward isocyanate groups under normal processing conditions, preventing CO2 generation and pinholes. For high NCO-index systems or prolonged oven-dry mixing, pre-drying SCS-3 to ≤0.2% moisture is recommended as an added precaution.

Oil Absorption	18–22 g/100g
Moisture Content	≤0.3%
Whiteness (R457)	≥95%
D50 Particle Size	3 µm
Stearic Acid Coating	2.0%

Stearic-Coated CaCO3 for Sealant Processing SCS-3

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