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A common purchasing request is simply:
“We need hydrophobic fumed silica. Which grade do you recommend?”
But hydrophobic fumed silica is not a single product.
IOTA currently lists multiple hydrophobic grades, including HB7132, HB7135, HB7139, HB7151, HB7152, HB7612, HB7615, HB7620 and HB7630.
To narrow down a suitable grade, the supplier first needs to understand the application.
Start by telling the supplier where the silica will be used.
For example:
The same hydrophobic silica grade should not automatically be assumed to be suitable for every formulation.
Provide basic information about the formulation.
For silicone applications, useful information may include:
This helps the supplier understand the formulation environment rather than recommending a grade only from a product specification.
Hydrophobic fumed silica may be selected for different reasons.
The customer may need:
Clearly identifying the main objective makes grade selection more focused.
Instead of simply saying “we need better silica,” describe the actual problem.
For example:
This information can be more useful than providing BET surface area alone.
If you already use another hydrophobic fumed silica, provide its grade or technical specification.
The supplier can then compare key characteristics and recommend a candidate for testing.
A replacement should still be validated in the customer's actual formulation rather than assumed to be a direct one-to-one substitute.
IOTA HB7135 is an HMDS-treated hydrophobic fumed silica with a listed BET surface area of 210 m²/g. Its published applications include silicone rubber, adhesives and sealants, defoamers and toner. The product page also highlights low thickening effect, processability and reinforcement in silicone rubber.
Whether HB7135 or another hydrophobic grade is more appropriate depends on the actual formulation and performance target.
Yes. Different applications and formulations can require different silica characteristics.
No. BET is useful, but surface treatment, formulation compatibility, rheology, processing and final performance also matter.
If available, yes. It gives the supplier a useful reference point for comparison.
It should not be assumed. Side-by-side formulation testing is recommended.
You can still provide non-confidential information such as application, polymer type, processing problem, current silica characteristics and desired performance.
Final selection should be confirmed through testing in the actual formulation and processing conditions.
