Polymer Initiators

Polystyrene (PS)

Polystyrene can be polymerized according to a free radical mechanism by two different processes:

• The bulk or mass process: This process is used for polymerization of GPPS and HIPS. In this case, styrene monomer used for polymerization is also acting as a solvent.
• Suspension polymerization: This process is used for polymerization of EPS where styrene is dispersed in fine droplets into water. The free radical initiators are exclusively organic peroxides that need to be soluble in styrene and insoluble in water. The size of the droplets can be adjusted by numerous parameters like addition of colloids, stirring conditions, reactor geometry, etc.

The polymerization temperature of these two processes are very different and consequently requires the use of different organic peroxides.

Bulk polymerization can be initiated either thermically or by the addition of organic peroxides. However, addition of organic peroxides provides numerous benefits and process flexibility.

Suspension polymerization is only initiated by organic peroxides.

• GPPS
• Longchain
• HIPS
• EPS