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.

Milled Perlite

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 ultra fine perlite fillers.

WHY PERLITE ULTRA FINE FILLERS?

Several important characteristics of ultra fine perlite make it extremely useful as a filler:

• very light weight
• reinforcing structure
• fine particle size
• high brightness
• mild abrasiveness
• lower volumetric cost
• availability

TYPICAL PRODUCT APPLICATIONS

Perlite ultra fine fillers have been used in a number of proprietary applications for many years. Some of these applications include:

• silicone rubber
• synthetic rubbers
• natural rubbers
• thermoplastic resins
  • polyethylene
  • PVC
  • others
• thermosetting resins
  • polyester
  • others
• paint
• coatings
• polishes
• cleansers