Definitions of HTIW

- Jun 11, 2018-

Classification temperature

The classification temperature is defined as the temperature at which a linear shrinkage of 4% is not exceeded after 24‑hour heat treatment in the electrically heated laboratory oven and in a neutral atmosphere. Depending on the type of product, the value may not exceed the following limits: 2% for boards and shaped products, 4% for mats and papers. The classification temperature is specified in 50 °C steps (starting at 850 °C and up to 1600 °C). The classification temperature does not mean that the product can be used continuously at this temperature. In the field, the continuous application temperature of amorphous HTIW (AES and ASW) is typically 100–150 °C below the classification temperature. Products made of Polycrystalline Wool can generally be used up to classification temperature.


Wool is an ordered accumulation of fibres of varying length and diameter. HTIW fulfil this definition and are therefore covered by the term “wool”. Amorphous AES and ASW are produced by melting the raw materials in a melting pot by means of electrical resistance melting. The jet of melt discharged from the pot is accelerated in a blowing or spinning process and pulled into fibres with different length/diameter ratios.

Continuous fibres/textile glass fibres (VDI 3469 Part 1)

These fibres are produced by means of the continuous filament process with defined nozzle diameters, all fibres having the technical defined and required diameter. During handling, only fibres of the given diameter but different length are released.