Perlite is a natural volcanic glass. There are many natural volcanic glasses around the world but the key feature for perlite is that when it is heated it expands. The expansive process is a lot like making pop corn. The resultant expanded perlite can be 20-30x its original bulk density. The process of expansion targets the combined water content within the raw perlite - the water trapped in the perlite ore - which vaporizes under heat and creates a glass bubble.
The expansion process normally takes place at when the perlite ore is rapidly heated to approximately 800-850˚C. For an ideal process, a combined water in raw perlite of 2.77-3.25% would be targeted. The resultant popped or expanded perlite, which is like a glass bubble, has extremely good insulating properties and is light weight. Expanded perlite can be engineered to a range of weights depending on the final application. This can range from 32-240kg/m3
For cryogenic insulation, for example, loose bulk densities can range for a cold box from 40-48kg/m3 which when considering an unexpanded perlite ore density of 1000-1100kg/m3 is quite a remarkable achievement. Blue Pacific Minerals produces perlite ore which is known to achieve the example loose density mentioned above in factory expansion situations as well as through portable on site expansion plants.
Once the perlite is expanded and has intrinsic characteristics of excellent insulation and light weight there are a number of potential applications. Expanded perlite can be used in the manufacture of low temperature (cryogenic) and high temperature insulation (formed and loose products), lightweight insulating concrete, lightweight insulating board, lightweight insulating plasters, and wall insulation.