Perlite is not a trade name but a generic term for naturally occurring siliceous volcanic rock. The distinguishing feature which sets perlite apart from other volcanic glasses is that when heated to a suitable point in its softening range, it expands from four to twenty times its original volume.

This expansion process is due to the presence of two to six percent combined water in the crude perlite rock. When quickly heated to above 1600 F (870 C) the crude rock pops in a manner similar to popcorn as the combined water vaporizes and creates countless tiny bubbles in the softened glassy particles. It is these tiny glass-sealed bubbles which account for the amazing lightweight and other exceptional physical properties of expanded perlite.

The expansion process also creates one of perlite's most distinguishing characteristics: its white color. While the crude perlite rock may range from transparent to light gray to glossy black, the color of expanded perlite ranges from snowy white to grayish white.

Expanded perlite can be manufactured to weigh from 2 lbs/ft3 (32 kg/m3) to 15 lb/ft3 (240 kg/m3) making it adaptable for numerous uses, including filtration, horticultural applications, insulation, inert carriers and a multitude of filler applications.

PERLITE AS A FILLER

There are several classes of perlite lightweight fillers:

1. What are often called ultra fine fillers are made by milling and classifying expanded perlite under stringent quality control conditions to create particles with jagged interlocking structures.

2. What are called perlite bubbles or perlite hollow spheres are similar in size to the ultra fine perlite fillers but they are discreet bubbles containing a multi-cellular core. They too are produced under stringent quality control standards to guarantee consistency and quality. In addition, they can be produced with special surface treatments to provide additional benefits in special mixes and formulations.

3. Finally, there are what might be called basic or general light-weight perlite fillers where traditional expanded perlite in sizes from 2000 microns down to 500 microns are used as fillers in products and mixes.

This Product Guide deals with perlite lightweight hollow spheres or bubbles as fillers.

Hollow Spheres of Perlite

ADVANTAGES OF PERLITE HOLLOW SPHERES OR BUBBLES AS FILLERS

1. Lightweight perlite fillers are effective bulk fillers because of their low density.

2. Lightweight perlite fillers exhibit a uniform white color that has minimal to no effect on the color of the fmished product

3. The particle shape of lightweight perlite fillers promotes good bonding between the perlite and resins.

4. Some properties such as impact resistance and tensile strength may be enhanced by the particle shape and size of lightweight perlite fillers.

5. Lightweight perlite fillers can reduce raw material costs while improving workability.

6. When used with other fire retardant materials, light weight, inert and inorganic perlite fillers can enhance fire resistance.

7. Perlite fillers are generally inert and perlite is listed in the U.S. Food Chemicals Codex.

Because of these characteristics, perlite lightweight hollow spheres or bubbles have been found to be cost effective in a number of applications including the manufacture of adhesives, auto body putty, cultured marble, coatings, patching compounds and stucco.

Decorative Ceiling Rosette and Cultured Marble Sink Made with Perlite Hollow Spheres

OTHER FORMS OF PERLITE FILLERS

Lightweight hollow perlite spheres or bubble fillers should not be confused with other types of perlite fillers. Hollow bubble fillers are produced under demanding quality control conditions utilizing special technologies. Only certain perlite filler manufacturers produce perlite bubble-type fillers. For additional in formation contact your local perlite supplier or the Perlite Institute.