FAQ: Technical Questions

Questions

1. What happens to glass cloth above its maximum operating temperature?
2. Does Microtherm^® have any sound absorption properties?
3. Can Microtherm^® withstand vibration?
4. Can Microtherm^® be waterproof?
5. Can Microtherm^® be recycled?
6. What is the maximum temperature limit for Microtherm^®?

Answers

1. What happens to glass cloth above its maximum operating temperature?
   
   For most purposes Microtherm^® uses E-glass cloth coverings. At temperatures above 600 °C the fibres of the cloth will begin to stick together, leading to brittleness and loss of strength on cooling. Some shrinkage may also be observed leading to splits in the cloth. These effects are more severe at higher temperatures. E-glass cloth will melt at temperatures exceeding 800 °C.
   
   Microtherm^® offers glass cloth coverings with higher temperature resistance for special applications.”
   
   The main consequence of these thermal changes to the glass cloth is that the strength and handleability of the insulation tends to revert to what it would have been without the glass cloth covering - the insulation performance is not altered in any way. Since Microtherm^® Insulation is usually held between metal sheets or refractory materials, deterioration of the glass cloth is normally not an important issue.
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2. Does Microtherm^® have any sound absorption properties?
   
   Microtherm^® Insulation is the world-leading high temperature thermal insulation due to its microporous structure. However, this highly porous interconnecting cellular structure also serves to absorb a certain amount of sound across the frequency spectrum. Microtherm^® Quilted Panel has been tested in accordance with BS EN 20354:1993 and ISO 354:1985 and the results are available on request. Microtherm^® Insulation is used in combination with other materials where acoustic and thermal protection are required in some of our passive fire protection systems for marine applications, particularly engine rooms.
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3. Can Microtherm^® withstand vibration?
   
   Microtherm^® insulation has been used extensively in applications on all forms of transport from aeroplanes to diesel locomotives where vibration is present. It has also been used on applications such as firedoors where impact vibration is encountered. As long as Microtherm is effectively contained it will not be damaged by vibration. We advise that if Microtherm^® insulation, in any of its varied forms, is to be applied to a surface which will be subject to vibration, then the Microtherm must be attached to the surface in such a manner that no movement of the Microtherm relative to the surface can occur, and in such a way that expansion of the Microtherm^® is prevented.
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4. Can Microtherm^® be waterproof?
   
   Microporous insulations absorb water which then causes an increase in thermal conductivity and damage to the structure. However, all microporous insulations can be encapsulated for protection in applications where water may be present. The disadvantage of this is the fact that the material used to protect the insulation will be destroyed as exposure temperatures increase.
   
   Microtherm^® is available in a hydrophobic grade which can be totally immersed in water for extended periods of time without harm. Although the special treatment which produces this hydrophobicity will be progressively destroyed when the insulation is exposed to temperatures above 250 °C, at a rate which increases with increasing temperature, this is a much higher temperature tolerance than can be obtained from wrapping materials such as plastic coverings and shrink wrap. It should also be remembered that the hydrophobicity will progressively disappear from the hot exposure surface inwards as exposure temperatures increase. In many applications, part of the insulation thickness will remain hydrophobic even with high hot surface temperatures.
   
   Further advice on this is available from our materials specialists.
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5. Can Microtherm^® be recycled?
   
   This is possible but not necessarily cost effective. Any Microtherm^® for recycling must be free from contamination and water damage and foreign objects. It should then be possible to re-process it. Further advice on this issue is available from our materials specialists.
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6. What is the maximum temperature limit for Microtherm^®?
   
   900 °C (1652 °F) for Microtherm^® G, and 1000 °C (1832 °F) for Microtherm^® Super G and Microtherm Board. Microtherm^® Super A has an upper temperature limit of 1150 °C (2102 °F). These figures are defined as the maximum temperature the insulation can take before it shrinks in diameter by more than 2 % in 24 hours full soak in a furnace according to ASTM C356, ISO 2477 or EN 104-6. This is an extremely demanding performance requirement.
   
   In most applications with single sided heating, Microtherm^® may withstand higher temperatures but we will not guarantee its performance as so many different factors can have an influence. Any comparison of temperature limits and shrinkage between products from different manufacturers should always be done with due reference to the standard against which the materials are tested. The working temperature limits that we quote for continuous exposure are defined as the maximum measured temperature at which the insulation shrinks less than 2 % in the dimensions perpendicular to the direction of pressing, in a furnace under full soak conditions according to all of ASTM C356, ISO 2477 and EN 1094-6.
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