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The idea is simple: more filler usually means lower cost and better reinforcement. In practice, many compounds turn stiff, hard to mix and difficult to deair as soon as loading goes up.
The filler itself is often the reason. Standard fumed silica builds viscosity quickly, so the compound hits its processing limit before the target loading is reached.
IOTA HB7132 is a hydrophobic fumed silica designed for exactly this situation: low thickening effect with excellent processability.
IOTA HB7132 is produced from hydrophilic fumed silica HL7200 after chemical post-treatment with HMDS (hexamethyldisilazane). The hydrophobic surface reduces hydrogen bonding between particles, which lowers the thickening effect in polymers.
Its published specifications:
|
Item |
Value |
|
Specific surface area (BET) |
160 m²/g |
|
pH value in 4% dispersion |
7.0–8.5 |
|
Loss on drying (105°C, 2 h) |
≤ 0.5% |
|
Ignition loss (1000°C, 2 h) |
≤ 4.0% |
|
SiO2 content (based on ignited material) |
≥ 99.8% |
|
Tamped density (based on dried material) |
40–60 g/dm³ |
|
Carbon content (based on dried material) |
2.5–4.0% |
These are typical values; the final compound must be verified by testing.
Stated applications and properties:
Two properties matter most for high-loading compounds: low thickening effect (the compound stays processable) and good transparency (the filled system stays clear).
A practical sequence:
1. Is HB7132 a treated grade?
Yes — it is hydrophobic fumed silica post-treated with HMDS. The treatment type is stated on the datasheet and should be confirmed for your application.
2. Can it be used outside silicone rubber?
Yes — defoamers, toner and adhesives/sealants are stated applications. Suitability in your specific system must be verified by testing.
Conclusion: when the limit is processability rather than reinforcement, a low-thickening hydrophobic grade such as IOTA HB7132 lets you push loading higher without losing the compound.
Related product: Fumed Silica IOTA HB7132
