Name: Fumed Silica Reinforcing Filler for Silicone Sealants FSR-200
Brand: Coatingsink
SKU: fumed-silica-sealant-reinforcement
Availability: InStock

Question 1

At what loading level does FSR-200 provide optimum mechanical reinforcement in RTV-1 silicone sealants?

Accepted Answer

Optimum reinforcement typically occurs at 20–30 phr on a PDMS base. Below 15 phr, tensile strength improvement is marginal; above 40 phr, viscosity rises sharply, processing becomes difficult, and elongation declines. In-situ treatment with silanol-terminated PDMS or hexamethyldisilazane (HMDS) during mixing reduces crepe hardening and improves long-term storage stability of the compound.

Question 2

How does BET surface area affect the thixotropic behaviour of silicone sealants?

Accepted Answer

Higher BET (200 m²/g vs. 130 m²/g grades) creates a denser hydrogen-bonding network between surface silanol groups, yielding stronger gel structure and higher yield stress. This gives better sag resistance on vertical joints but requires higher shear during mixing. FSR-200 is preferred where non-sag performance is critical; lower-surface-area grades suit pourable or self-levelling formulations.

Question 3

Can FSR-200 be used in both acetoxy-cure and neutral-cure silicone sealant systems?

Accepted Answer

Yes. Being unfunctionalised (hydrophilic surface), FSR-200 is compatible with acetoxy-cure (acetic acid release), oxime-cure, alkoxy-cure, and amine-cure systems. In acetoxy systems, surface silanol groups may slowly esterify over time but reinforcement is not impaired. For applications requiring minimal moisture uptake in the cured product or improved weatherability, surface-hydrophobised grades treated with HMDS or PDMS oligomers are preferred.

SiO₂ Content	≥99.8%
Tapped Density	~50 g/L
BET Surface Area	195–205 m²/g
pH (4% dispersion)	3.7–4.5
Loss on Ignition (1000°C)	≤1.0%

Fumed Silica Reinforcing Filler for Silicone Sealants FSR-200

Specifications

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