The microporous effect ...
is the restriction of collisions between air molecules which would lead to heat transfer by gaseous conduction.
Although Microtherm® is solid and has excellent compression resistance it is fairly low in density and actually around 90% trapped air.
It is formed from nano-sized particles of silica that are bonded under compression into long tangled chains. The air is contained as minute pockets in the structure that are smaller in size than the mean free path of an air molecule, the distance it must travel to collide with another air molecule. This pore structure dramatically limits the effect of gaseous conduction and eliminates internal convection. Instead of colliding with each other, air molecules collide with the walls of the pores, a process which transfers little energy.
Solid conduction is minimised by the low density, but also by the minute particle structure. The very small area of contact between particles together with the length of the particle chains effectively limit heat transfer by solid contact.
Radiation is the principal way that heat moves at higher temperatures and is the reason for the rapid deterioration of performance of conventional insulation materials in these conditions.
By incorporating particles of an opacifier material in the structure of Microtherm® it becomes almost totally opaque to infra-red radiation. The opacifier repeatedly refracts (bends) the infra-red wave, blocking its transfer through the insulation almost completely.
As a result, Microtherm® has an even lower thermal conductivity than still air.