Expandable microsphere

Expandable microspheres are microscopic spheres comprising a thermoplastic shell encapsulating a low boiling point liquid hydrocarbon. When heated to a temperature high enough to soften the thermoplastic shell, the increasing pressure of the hydrocarbon will cause the microsphere to expand.[1] The volume can increase by 60 to 80 times.

Expandable microsphere

The expandable microsphere is a material that can act as a blowing agent when mixed in a product and subsequently heated to cause expansion within the matrix. The expandable microspheres are off-white, can be 6 to 40 micrometers in average diameter and have a density of 900 to 1400 kg/m3. The expandable microspheres are used as a blowing agent in products like e.g. puff ink,[2] automotive underbody coatings or injection molding of thermoplastics.[3] Here the product must be heated at some point in the process for the expandable microspheres to expand.

Expanded microsphere

The expanded microsphere is a material that has been heated to cause expansion. The product acts as a light weight filler in many products. The expanded microspheres are white, can be 15 to 90 micrometers in average diameter and can have a density of 15 to 70 kg/m3. The expanded microspheres are used as a lightweight filler in composite materials such as cultured marble, in waterborne paints and crack fillers/joint compound.

Characteristics

Characteristics that make expandable microspheres unique,

  • Ability to expand
  • Resilient
  • Ultra-low density when expanded
  • Closed cells that can be distributed evenly
  • Can introduce a pressure in the production process

References
  1. Patent US 3,615,972 "Expansible thermoplastic polymer particles containing volatile fluid foaming agent and method of foaming the same"
  2. Expandable microspheres in inks: advances in look and feel, Asia Pacific Coatings Journal, August 2009, page 32-33
  3. "New developments with expandable microspheres", Klas Elfving, Expancel. The Fifth International Conference Blowing agents and Foaming Processes 2003, Rapra.

See also
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