# Polystyrene and EPS: Production route

Clear, toughened or foamed: three ways to make PS

Source page: https://www.materialinsights.org/chemicals/polystyrene/routes/

What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.

The main product types are general-purpose PS (GPPS, clear and brittle), high-impact PS (HIPS, toughened with polybutadiene rubber) and expandable PS (EPS, beads with pentane for foam). GPPS and HIPS are made by continuous bulk polymerisation; EPS by batch suspension polymerisation. Extruded PS foam (XPS) is made from GPPS by converters. Recycling options include mechanical recycling of clean streams and thermal depolymerisation back to styrene, which works better for PS than for most plastics.

#### Routes compared

| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| **General-purpose PS (GPPS), continuous bulk polymerisation** | about 30-35% of PS and EPS volume (indicative) | about 1.0 t styrene, about 0.15-0.25 MWh and some heat per t (indicative) | 100-300 kt/yr lines (indicative) | about 99% after monomer recycle (indicative) | styrene oligomers in small amounts | styrene cost plus about $100-200/t conversion (indicative) |
| **High-impact PS (HIPS), bulk polymerisation with rubber** | about 25-30% (indicative) | about 0.9-0.93 t styrene and 0.07-0.10 t polybutadiene rubber (indicative) | 100-300 kt/yr (indicative) | about 99% (indicative) | minor | slightly above GPPS (indicative) |
| **Expandable PS (EPS), suspension polymerisation** | about 40-45% (indicative); global EPS capacity about 10.6 Mt in 2021 (GlobalData) | about 0.93-0.95 t styrene, 0.05-0.07 t pentane, flame retardant about 0.5-1% (indicative) | 50-200 kt/yr (indicative) | about 98% (indicative) | off-size beads (recycled), process water | styrene plus about $150-250/t (indicative) |
| **Recycled PS (mechanical and depolymerisation)** | small (indicative) | baled or densified PS waste | pilot to tens of kt/yr (indicative) | depolymerisation can recover a large share as styrene (indicative) | residues, oligomers | not published |

#### How each route works
**General-purpose PS (GPPS), continuous bulk polymerisation**

Styrene with a little solvent is polymerised thermally or with initiators in stirred or plug-flow reactors, then devolatilised under vacuum to below about 500 ppm residual monomer (indicative).

Simple and clear; brittle; competes with PP and PET in packaging.
 indicative (industry standard) **High-impact PS (HIPS), bulk polymerisation with rubber**

5-10% polybutadiene is dissolved in styrene before polymerisation; rubber particles graft and toughen the matrix.

Cheap impact-resistant plastic for appliances and packs; replaced by ABS or PP where heat or chemical resistance matters.
 indicative **Expandable PS (EPS), suspension polymerisation**

Styrene is polymerised as droplets in water, with pentane added to make expandable beads; building grades contain polymeric brominated flame retardant (replacing HBCD, banned under the Stockholm Convention). Graphite-filled grey EPS improves insulation.

Cheapest insulation per R-value and very light; pentane is a VOC and foam waste is bulky.
 GlobalData via Offshore Technology; indicative **Recycled PS (mechanical and depolymerisation)**

Clean EPS is densified and re-extruded into GPPS-type pellets; dissolution and thermal depolymerisation recover styrene monomer from mixed PS waste.

PS depolymerises cleanly, but collection of light foam is the bottleneck.
 indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.

## Other sections

- [Summary](https://www.materialinsights.org/chemicals/polystyrene/index.md)
- [Overview](https://www.materialinsights.org/chemicals/polystyrene/overview/index.md)
- [Correlation](https://www.materialinsights.org/chemicals/polystyrene/correlation/index.md)
- [Production](https://www.materialinsights.org/chemicals/polystyrene/production/index.md)
- [Feedstocks](https://www.materialinsights.org/chemicals/polystyrene/feedstocks/index.md)
- [Cycles](https://www.materialinsights.org/chemicals/polystyrene/cycles/index.md)
- [Trading](https://www.materialinsights.org/chemicals/polystyrene/trading/index.md)
- [Movement](https://www.materialinsights.org/chemicals/polystyrene/movement/index.md)
- [Regulation](https://www.materialinsights.org/chemicals/polystyrene/regulation/index.md)
- [Characteristics](https://www.materialinsights.org/chemicals/polystyrene/characteristics/index.md)
- [Emissions](https://www.materialinsights.org/chemicals/polystyrene/emissions/index.md)
- [Relationships](https://www.materialinsights.org/chemicals/polystyrene/links/index.md)