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Product Description
Benefits & Application Details



ATH (aluminium trihydrate, chemical formula Al(OH)3
) is an intermediate product of aluminium production, characterised by:

  • High purity
  • High whiteness
  • Relatively low density of 2.4 g/cm3 compared to other mineral fillers, which are typically at 2.7 g/cm3
  • Medium Mohs Hardness of 3
  • Decomposition around 200°C, releasing water.


Basic properties

Property Value Unit
Moisture < 0.4 [%]
pH 9 [-]
Hardness (Mohs) 3 [-]
Refractive index 1.57 [-]
Electrical conductivity 60 [µS/cm]
L.O.I. 34.5 [%]
Density 2.4 [kg/ dm3]


Portaflame SG and Boratherm SG  are the product names for Sibelco’s milled ATH-based products.

Portaflame SG and Boratherm AG are the product names for Sibelco’s milled ATH-based products. Portaflame SG is used as a flame retardant mineral in a wide variety of applications. Boratherm SG products are used to increase the thermal conductivity of polymer based composites.  Depending on processing conditions and requirements for the final application  4 different subgroups have been developed to meet the expectations of the formulator, converter /applicator and end-customer. They are a cost-effective replacement for precipitated ATH.


Additional benefits when using Portaflame SG or Boratherm SG:

  • Chemical resistance: due to its inert nature, ATH provides good chemical resistance compared to conventional fillers.
  • Low abrasion due to its low hardnesss of 3 on the scale of Mohs.
  • UV-curing compatibility: being transparent for UV radiation, ATH does not block the curing mechanism


Product variants

ATH, fine

Sibelco’s Fine ATH range consists of products with a defined PSD, topcut, colour, Oil absorption and BET. The fine ATH-grades are typically used in applications critical to surface defects, colour, impregnation or FR-performance, often replacing fine precipitated ATH-grades.

ATH, medium /coarse

Sibelco’s Medium and Coarse ATH-range consists of products with a defined PSD and relatively high bulk density. These products are typically used in applications where easy handling of the product and economics are important.

ATH, Low Viscosity (LV & LVS)

Sibelco’s Low Viscosity ATH-range consists of products optimized for low Oil Absorption values. By dedicated milling particle shape and PSD are optimized for optimal packing performance. With Sibelco’s Low Viscosity products the formulator can achieve higher filler loading levels in different resin systems.

ATH, Elctrical

Sibelco’s Electrical ATH-grades consist of coarse E-grades with a steep particle size distribution well controlled on topcut and demagnetized. These grades are especially suitable for encapsulation of electrical component.

Furthermore in the ATH Electrical range Sibelco produces a fine milled ATH with special silane treatment optimized for application in silicone HVI and elastomers.

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