Thermal Ceramics

Low biopersistent fibre in a class of its own

Superwool XTRA - engineered for superior chemical resistance and zero respirable crystalline silica formation.

Over the last two decades, our journey of continued research and development to pursue alternatives to Refractory Ceramic Fibres (RCF) has essentially supported the improvement of our Low Biopersistent (LBP) Fibres, Alkaline-Earth-Silicate (AES) grades Superwool® Plus and Superwool Primes by developing manufacturing methods, raw materials, process control, in-service performance, market needs, energy saving insulation amongst many more capabilities.

Thermal Ceramics has extended its product range with Superwool XTRA, a Potassium-Alumino-Silicate (PAS) high-temperature LBP fibre with a classification temperature of 1450°C (2600°F) and comparative, if not better, pollution resistance than RCF.

Superwool XTRA has a unique chemical composition different than any LBP fibre on the market today. Superwool XTRA that can now replace many RCF 1400°C (2550°F) applications with an LBP, exonerated fibre.

  • Exonerated from carcinogen classification and not classified as hazardous by IARC or under any national regulations on a global basis
  • Superwool XTRA does not form crystalline silica when exposed to high temperatures
  • Our Superwool XTRA fibre has been proven in targeted applications, with over 4 years of success
  • Proven to perform better than RCF with most industrial furnace pollutants, especially alkali metals
  • With higher thermal expansion, Superwool XTRA heals shrinkage gaps in the furnace insulation as the furnace heats up
  • High melting point for high over-temperature protection >1650°C (3000°F)
  • Designed to replace RCF 1400°C (2550°F) applications
  • A patented fibre classification of its own

Superwool XTRA Product Portfolio

Frequently Asked Questions on Superwool XTRA


What is low biopersistent fibre?

  • Developed in the 1980s and made commercially available from the early 1990s
  • Used in consumer goods, transportation, energy, metals and other industrial applications
  • Exonerated from Carcinogenic classification globally
  • Low Biopersistence (LBP)
  • Can be used up to 1450°C (2600°F)

Under Note Q, LBP fibress must contain more than 18 weight-% alkali metal or alkaline earth oxides and meet requried low biopersistence criteria. The most commonly known example of LBP fibres are AES fibres, which consist of amorphous fibres produced by melting a combination of CaO-, MgO- and SiO2 (see also EN 1094-1; VDI-recommendation 3469, Parts 1 and 5; per ECFIA website ).

How is Superwool XTRA different than Superwool Plus and Superwool Prime?

Not all low biopersistent fibres are the same.

Superwool Plus and Superwool Prime, both an Alkaline-Earth-Silicate (AES) fibre, and Superwool XTRA is a Potassium-Aluminosilicate (PAS) fibre. Both are low biopersistent.

Superwool XTRA fibres do not form crystalline silica at any stage

Does Superwool XTRA form crystalline silica?

Due to the unique fibre chemistry, Superwool XTRA does not form crystalline silica. Extensive testing, over 7000 hours at 1250°C, show no formation of crystalline silica.

How do you explain the thermal expansion and shrinkage of Superwool XTRA?

With Pyro-Bloc Modules and Pyro-Stack Modules, due to the unique fibre chemistry, the shrinkage is permanent and only happens on the first firing and when the material transforms from amorphous state to crystalline. The thermal expansion is a fundamental material property and it is a function of temperature and will continue to occur in every heating cycle and the shrinkage gaps close.