definition
strict definition
perlite loose fill
Loose expanded perlite particles used as thermal insulation, made by heating naturally occurring volcanic glass.
Perlite loose fill is a thermal insulation material made from expanded grains of perlite, a naturally formed amorphous (non-crystalline) volcanic glass which expands when heated. It typically contains high levels of silicon oxide and aluminum oxide. It is generally light in color, usually white or yellowish.
Heating expands the perlite into lightweight porous particles. The pores reduce the bulk density of the resulting loose insulating material.
The particles remain loose within the space being insulated. Perlite incorporated into a bonded board or another manufactured assembly has a different material form.