Polymer Initiators

EPS

There are two ways to produce expanded Polystyrene:

The first one is the foaming of GPPS during extrusion, the product is called XPS

The second one is by suspension in presence of a foaming agent (EPS)

The typical process for EPS is a 2-step batch process in water with the following conditions:

• 1st Step: Polymerization at 80-90°C for up to 6 hrs: BPO (Luperox^® A75)
• 2nd Step: Reaction completed at 120-130°C for up to 3 hrs: Perbenzoate (Luperox^® P) or monoperoxycarbonates (Luperox^® TBEC, Luperox^® TAEC)

Initiators of different activities can be added at the beginning, and a second initiator can be added just prior to the second step. Due to the presence of foaming agent, flame retardant and other volatile additives no stripping is possible. Beads are simply dried. (Yield: 100%)

For flame retardant grades, the extra addition of Luperox^® DC activates hexabromocyclododecane as FR. These remain fully intact during polymerization, but are evenly distributed in the EPS beads.

Industry requirements

Moderate molecular weight and molecular weight distribution lower concentration of residuals (styrene, decomposition products)