The dramatic expansion when heated and the other unique properties of EXPANCEL® microspheres are due to a small amount of a hydrocarbon encapsulated by a gastight thermoplastic shell. When the microspheres are heated the thermoplastic shell softens and the hydrocarbon inside the shell increases its pressure. This results in a dramatic expansion of the spheres (typical diameter values: from 10 to 40 µm), with a corresponding dramatic decrease of the density (typical values: from 1000 to 30 g/liter).
The different EXPANCEL® microsphere grades vary according to:
expansion factor
heat resistance
particle size
chemical and solvent resistance.

Thermomechanical properties
There are grades of EXPANCEL® microspheres available with expansion temperatures in the range of 80 -190°C (176 - 374°F).
The temperature at which expansion starts as well as the temperature at which the maximum expansion and the lowest density is obtained depends to some degree on the heatingrate. At temperatures above the temperature at which the highest expansion is obtained the microspheres gradually collapse.

Resilience
All EXPANCEL grades are highly resilient. The expanded microspheres are easy to compress. When the pressure is reduced the microspheres regain their original volume.
Due to this resiliency, EXPANCEL® microspheres can withstand some thousand cycles of loading/unloading without collapsing or breaking, under normal circumstances. This is very important when the microspheres are used in shock absorbent materials but also when pumping them, alone or in various mixtures.

Chemical resistance
EXPANCEL® microspheres can be used in contact with many chemicals, including solvents, without negative effects on expansion or other properties.