South African Palabora vermiculite was modified by ion exchange with ammonium and
selected alkali metal and alkaline earth metal ions. In the exchanged vermiculite with
ammonium ions, it was found that ammonia and water were the blowing agents and
they were simultaneously released during thermal degradation. In the increasing ionic
potential series: Na, Ba, Ca and Mg, it was found that the onset expansion temperature
also increased dramatically. Exchange with relatively low ionic potential species,
namely sodium, potassium and ammonium, lowered the exfoliation onset temperature
of vermiculite to below 300◦C.