The light, frothy character of expanded perlite (low-density, glassy particles with cellular interiors) combined with its inorganic permanence, chemical inertness, bright white color, ready absorption of binders, and acoustical and thermal insulating properties make it popular for lightweight, volume-stretching filler. Various perlite grades and varieties—from coarse aggregate bubbles to an ultrafine milled flake—are available to meet density specifications. Perlite binds readily with cements and plasters, asphalt, liquid sodium silicates, potassium silicates.
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Lightweight Formed Products
According to a publication from the Perlite Institute, over half the perlite expanded in the U.S. is destined for use in formed products like ceiling tiles, pipe insulation, insulating roof panels, manufactured stone, resin-based castings, cultured marble, and fire-rated door cores. Lightweight perlite granules are combined with a variety of binders that provide the final shape.
The functional advantages of expanded perlite in formed products include effective bulk at a low density, uniform white color that readily accepts dyes and colorants, excellent integration with binding resins, strength and impact resistance, enhanced fire resistance, inert and safe to dispose of and to handle.
Coating and Filler Applications
Perlite is a chemically inert flatting filler with high oil absorption and good dry hide. Used in fire-resistant coatings for structural steel and concrete as well as in insulating renders, expanded perlite also finds a home as a filler in putties, patching compounds, caulks, textured paints, and in plastisol coatings used to improve sound insulation.
Cement-and-fiber boards provide several advantages—durability, impact resistance, fire, water, vermin, and fungus resistance as well. The most frequently cited disadvantage? Weight. Cement sheet goods are almost twice as heavy as gypsum-based board systems. That has cement board product manufacturers incorporating puffy perlite into lightweight formulations—expanded perlite, cement, a silica solution, a thickener and a hydrophobing agent. The slurry is then pressed in a mold for shaping and left to harden before it is finished in a dryer.