Perlite sold to the general industrial market is under the tradename PROVOSIL. This pure white inorganic material is a PROcessed VOlcanic SILicate with countless closed-cell voids formed by expansion under intense heat. PROVOSIL expanded perlite is low in density; it can be produced in weights below 2 pounds per cubic foot. It is low in thermal conductivity, and low in cost because of its high bulking characteristics. PROVOSIL may be used throughout a temperature range of minus 400 degrees F to plus 2,000 degrees F without significant change of properties.
If you were to look at an enlarged view of a cross section of a particle of PROVOSIL you would see an internal cellular structure with the cells on the outside of the particle fractured. The closed cellular particles of PROVOSIL resist penetration, yet substantial moisture may be held in the fractured outside cells. Although normal PROVOSIL particles have a large surface area (which can be useful in many applications) we can specially treat these particles to make them hydrophobic (enclose the outside cells to resist adsorbtion).
In typical industrial applications, PROVOSIL fillers provide some or all of the following benefits: