THERMOSIL High Density Arc and Heat Resistant Boards are manufactured from carefully selected and treated Raw Asbestos Fibre and special grades of cement. The particular properties of the material are obtained by maintaining precision control of the blend, rate of mixing, addition of predetermined quantities of water and chemicals and then compressing the mix into sheet form under extremely high pressure. The sheets are then kept for maturing for several weeks under conditions of controlled humidity and temperature.

THERMOSIL High Density Boards are versatile materials which combine the following distinctive properties not available in any other individual material:

The distinctive properties of THERMOSIL High Density Boards lead to their applications in numerous diverse areas. Some of these applications are:

THERMOSIL High Density Boards are available in the following grades:

HD-31   General purpose natural grade suitable for most of the required applications.

HD-35   Special grade for specific requirements. Only manufactured against order.

The natural grade has high water absorption which can result in unsatisfactory electrical insulation if used in situations where such water absorption can occur. Silicone Resin impregnated material (SR Grade) is recommended for such applications. This eliminates the necessity of coating the edges with varnish after cutting.
Silicone Resin has been chosen because it has a higher operating temperature in comparison to other available Resins.
The minute pores in the Boards are filled with Silicone Resin, increasing the electrical strength and lowering moisture absorption from 15% to about 1%. There is also some burning of Resin at the point of contact with the arc but this is localized and is self extinguishing.
SR grade does not replace HD grades but is intended for application where superior electrical properties are required such as in arc chutes and barriers for H.V. air break switchgear.
SR grade is available in thickness range of 3.2 mm to 38 mm.