Perlite

Perlite (English: perlite ) referred in the geosciences one -altered ( chemically and physically transformed ) volcanic glass ( obsidian ) and ranks among the rocks. It is used for many purposes, for example in the building trade as raw material.

Natural Occurrence

The hard obsidian is decomposed by small cracks in approximately pea size glass beads, or shards in the course of conversion, and then shows the typical structure of perlitic. Due to ingress of water along the cracks is a devitrification this form from the amorphous glass microscopic crystals of quartz, cristobalite and feldspar. In advanced stages, the conversion result is a loose rock of bluish green, brownish or gray color.

Nature itself makes volcanic activity lasting for replenishment, so perlite can be described as inexhaustible resource. The derived products are easily traceable nature (eg for soil improvement for gardening, farming and composting, as well as ventilation and humidity control ).

Properties and Uses

Perlite contains up to 2% water and has a density of about 900 to 1000 kg / m³ ( bulk density of the raw perlite ). By annealing at about 800 ° C to 1000 ° C, pearlite inflates to fifteen to twenty times its original volume and then has a bulk density of 50 to 100 kg / m³ and the thermal conductivity λ = 0.040 to 0.070 W / mK.

Perlite, raw or bloated, is mainly used among others in the form of silicone- impregnated beads with about five millimeters in diameter for thermal insulation, for example, as a bed in residential construction in ceilings or floors and the core insulation. It also serves as fire protection. A significant use is as expanded perlite fillers and aggregates in the construction industry for the manufacture of paints, varnishes, plasters and dry mortar.

In the beverage food production approach uses perlite back as a filter aid.

In shipping, perlite is used in the construction of LNG carriers for tank insulation. The perlite is impregnated with silicone in order to prevent the absorption of water as far as possible.

As insulation using perlite in the refrigeration industry. One example is the filling of the cold chambers for air separation plants.

In horticulture, it serves as a sterile sowing substrate or as an additive to potting soil, which protects against excessive compaction and improves the air permeability.

In the steel making slag perlite is used as binder.

A relatively new application of perlite can be found in the production of anti-perspirant sprays.

It is also used in special tooth pastes for the removal of deposits and discolouration.