Polymer materials suited for use as high temperature insulation

Geopolymers with the potential for use as refractory castable

From the most technologically aware city dwellers to remote jungle tribes, almost the entire population of the earth know polymeric materials as plastics. Although some plastics are oven proof and can readily withstand high temperatures, they generally melt or burn at extreme temperatures.

Inorganic polymers are different and show promise for use in elevated temperature applications. Inorganic polymers made from aluminosilicates are termed geopolymers. They are amorphous to semi-crystalline and consist of two or three dimensional aluminosilicate networks, dependent on the composition. Geopolymers can be formed using a relatively low temperature processing techniques.

Physical behaviour of geopolymers are similar to those of Portland cement. Consequently, they have been considered as a possible improvement on conventional cements with respect to compressive strength, resistance to fire, heat and acidity, as well as a medium for the encapsulation of hazardous or low/intermediate level radioactive wastes. Although many applications have been speculated upon, their widespread use is restricted due to a lack of long term durability studies, detailed scientific understanding and lack of reproducibility of raw materials.

In this work published in AZojomo*, by Dan Perera and Rachael Trautman from Australian Nuclear Science and Technology Organisation (ANSTO), geopolymers are investigated for suitability as refractory coatings and as low temperature (1000°C) refractory castables.

The researchers found that geopolymers heated up to 1400°C did not show any major melting. The presence of two refractory phases, kalsilite and leucite, and an open porosity of ~38% at 1000°C, should make this material suitable as a refractory or heat insulation material for continuous use at this temperature.