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When customers ask for fumed silica, one of the most common descriptions is:
“I need 200 m²/g fumed silica.”
BET surface area is certainly an important specification.
But for application-based material selection, BET alone is usually not enough.
Two fumed silica products with similar BET values may behave differently in the same formulation. IOTASILICA has recently discussed how surface characteristics, aggregate structure, moisture and dispersion can influence formulation behavior.
The first question should be:
Where will the fumed silica be used?
For example:
The required function can be very different between these systems.
The same fumed silica may behave differently in:
Compatibility between the silica surface and the formulation is therefore important.
Instead of only saying:
“I need 200 m²/g.”
It is more useful to explain whether the formulation needs:
The same BET value does not guarantee the same result for every function.
This is especially important for formulation replacement.
IOTASILICA's product portfolio includes both hydrophilic fumed silica and hydrophobic fumed silica, including grades such as HL7200 and HB7135/HB7139/HB7151.
The surface treatment can influence:
Therefore, when replacing an existing grade, the surface treatment should be considered together with BET.
The amount of fumed silica can strongly affect formulation behavior.
If a customer is evaluating an alternative supplier, it is useful to provide:
This allows a more meaningful comparison.
A practical qualification process can start with:
COA comparison → same-dosage trial → same processing conditions → application-property comparison
Depending on the formulation, relevant properties may include:
IOTA HL7200 can be evaluated when a customer is looking for a hydrophilic fumed silica with similar specification requirements.
Rather than assuming direct replacement based only on BET, a parallel formulation trial is recommended.
For customers currently using hydrophobic fumed silica, the same principle applies.
The evaluation should include:
BET + surface treatment + formulation compatibility + dispersion + rheology + finished-product performance
This is especially important when selecting silica for silicone rubber, sealants, adhesives, or other systems where surface chemistry strongly affects processing.
Product Reference: IOTA Hydrophilic and Hydrophobic Fumed Silica
Final product selection should be verified according to the customer's formulation, processing conditions, and finished-product requirements.
