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A new fumed silica passes the first laboratory test.
The sealant looks good immediately after mixing.
But after storage, the customer notices that its behavior has changed.
This raises an important question:
If the initial test passed, why did the formulation change later?
The answer may involve more than the silica's basic specification.
When evaluating a new silica, customers often compare the formulation immediately after production.
They may check:
These are useful tests.
But for a commercial sealant, the material also needs to remain acceptable after storage.
Hydrophilic and hydrophobic fumed silica have different surface characteristics.
These differences can affect how the silica interacts with:
For formulations where moisture sensitivity or long-term compatibility matters, a surface-treated hydrophobic grade may therefore be worth evaluating.
That does not mean hydrophobic silica is automatically better.
It means the surface chemistry should match the formulation requirement.
A silica that is not properly incorporated into the formulation may appear acceptable immediately after mixing but show differences later.
When changing suppliers or grades, keep the first comparison controlled:
Same formulation → Same dosage → Same mixing sequence → Same equipment → Same storage conditions
This helps separate the effect of the raw material from the effect of the process.
Do not evaluate only Day 0.
Depending on the product and customer's own quality procedure, useful checkpoints may include:
Initial → Stored samples → Recheck processing → Recheck rheology → Recheck cured performance
The exact aging conditions should follow the manufacturer's own product-validation procedure.
It may be worth testing when the formulation requires a different balance of:
IOTA supplies both hydrophilic and hydrophobic fumed silica, allowing the starting grade to be selected according to the actual formulation rather than using one silica type for every sealant.
If a silica passes the initial test, is the replacement confirmed?
Not necessarily. Storage and finished-product performance should also be evaluated.
Does hydrophobic silica automatically improve shelf life?
No. Shelf life depends on the complete formulation, packaging and storage conditions.
Why compare silica under the same processing conditions?
Changing several variables simultaneously makes it difficult to identify the cause of performance differences.
Should hydrophilic silica be excluded from sealant formulations?
No. Suitable hydrophilic grades can perform well depending on the formulation.
What information should be provided when evaluating a hydrophobic grade?
Sealant type, cure chemistry, current silica, dosage, process, storage problem and target properties.
Related Products:
IOTA Hydrophobic Fumed Silica Series
IOTA HL7200 Hydrophilic Fumed Silica
Application boundary: Storage stability and shelf life are properties of the complete formulation and package. Fumed silica selection should be confirmed through the customer's own aging and finished-product tests.
