Perlite is the volcanic glass containing 65-75 % of SiO2 and 2-5 % of H2O. The characteristic property of perlite is that if subject to rapid heating of 900 to 1.200°C it increases its volume 4 to 20 times. This happens because perlite includes the bound water which extends during heating according to a well-known popcorn effect and adopts the form of a porous swollen material. The size of swollen pellets varies between 1 and 10 mm, with apparent density of 75 to 150 kg/m3. Thanks to these numerous tiny voids the volcanic rock becomes light and acquires unique thermal and sound-proofing properties. Besides it has perfect refractory properties, chemical inertness and is not damaged by animal pests, among other things.
Perlite advantages
Typical physical properties of perlite
| ¹ ï/ï | Property | Value | |
1 | Colour | White | |
2 | Brightness, % GE | 70-80 | |
3 | Apparent density, kg/m3 | 50-300 | |
4 | (Mohs) hardness index | 5,5 | |
5 | pH | Neutral | |
6 | Water absorption, % of mass | 200-600 | |
7 | Ability to absorb oils, gram of oil per gram of perlite | 50-100 | |
8 | Melting point, C° | 980 | |
9 | Burn losses (3 hours under t of 900°C), % | up to 1,5 | |
10 | Humidity, % | up to 1,0 | |
11 | Maximum strength, MPa | up to î 6,0 | |
12 | Porosity, % | 70-85 | |
13 | Portion of air, % | 80-95 | |
14 | Thermal conductivity, W/mK | 0,043-0,093 | |
15 | Thermal diffusivity, m2/sec | 0,632-0,330 | |
Typical chemical properties of perlite
| Element composition, % | Chemical composition, % | ||||
Silicon | Si | 33,8 | Silicon dioxide | SiO2 | 72,08 |
Aluminium | Al | 7,2 | Alumina | Al2O3 | 12,92 |
Potassium | K | 3,5 | Titanium dioxide | TiO2 | 0,90 |
Sodium | Na | 3,4 | Iron oxide | Fe2O3 | 1,50 |
Iron | Fe | 0,6 | Magnesium oxide | MgO | 0,63 |
Calcium | Ca | 0,6 | Quick lime | CaO | 0,88 |
Magnesium | Mg | 0,2 | Caustic soda | Na2O | 3,76 |
Mica | - | 0,2 | Potassium oxide | K2O | 4,33 |
Oxygen | O | 47,5 | Bound water | H2O | 3,0 |
