Additives Agents for Extruded Expandable Polystyrene


In EPS production, optimum cell nucleation is key to superior finished product properties and performance. For over 40 years, NuCera polymers have provided the full range of advantages  required to produce the world’s finest EPS

This new platform offers formulators flexibility to balance performance and sustainability, and is easily formulated into skin care, sun care, and color cosmetic products.

  • Extruded polystyrene foam begins with solid polystyrene crystals. The crystals, along with special additives and a blowing agent, are fed into an extruder. Within the extruder, the mixture is combined and melted, under controlled conditions of high temperature and pressure, into a viscous plastic fluid. The hot, thick liquid is then forced into a continuous process through a die. As it emerges from the die it goes through pelletizing to make the beads, then expands to a foam, is shaped, cooled, and trimmed to dimension.
  • Polywax PE is used as nucleant agent and as a lubricant agent in extruded PS to improve the cell structure, reduce the density and enhance polymer properties, obtain reduced shear, higher output, better temperature control of the melt, and lower melt friction. And to make it shinier, a better fusion between the beads


  • Dispersion agent for additives like carbon black , graphite and flame retardants
  • Enhancing polymer properties
  • Reduced shear, higher output
  • Improved density potential and thermal conductivity values
  • Better foam strength at a given density
  • Faster mold cooling time
  • Improved molding fusion and gave the shiner color

NuCera POLYWAX™ polyethylenes are fully saturated homopolymers of ethylene that exhibit a high degree of linearity and crystallinity. These synthetic waxes have narrow molecular weight distributions with a typical polydisperity  (Mw/Mn) of 1.08. In application, POLYWAX polyethylenes exhibit sharp melting point, fast recrystallization, low melt viscosity, excellent heat stability and resistance to chemical attack.

When used  in EPS production, POLYWAX polyethylenes promote the formation of small, uniformly sized cells, providing better surface finish and lower density of the final product.

Effect on EPS Cell Structure
The photos below are of EPS beads, taken with a Scanning  Electron  Microscope  (SEM),  Note the development of small uniform cells when POLYWAX polyethylene is used as the nucleant.

0.3% ppm POLYWAX2000 polyethylene

0.3% ppm POLYWAX  2000 polyethylene

0.3% ppm POLYWAX 2000 polyethylene

0.3% ppm POLYWAX 2000 polyethylene

Typical Properties

The choice of nucleant depends on EPS manufacturing processing conditions. Industry standard grades are listed below; however, other grades of varying molecular weight are available to meet the needs of various production processes.

Product / Test Method Melt Point °C / ASTM D-127 Viscosity cP @ 149 °C / ASTM D-3236 Penetration dmm @ 25°C / ASTM- D1321
POLYWAX™ 2000 polyethylene
POLYWAX™ 3000 polyethylene

Recommended Applications And Use Levels

Product Form

In addition  to molecular weight, the product form can also impact the effectiveness of the nucleant in the EPS process.  

POLYWAX polyethylenes are available in three physical forms:

  • Prills – average particle size of 3 mm
  • Mini prills – average particle size of 1 mm
  • Micronized– certain grades are available in a micronized form


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