# Polyethylene (LDPE, LLDPE): Production route

Crushing pressure versus clever catalysts

Source page: https://www.materialinsights.org/chemicals/polyethylene/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.

All LDPE and LLDPE starts from ethylene. LDPE uses free-radical polymerisation at very high pressure, which gives branched chains, clarity and easy processing. LLDPE uses catalysts at low pressure and a short-chain comonomer, which gives linear chains with short branches and much higher toughness at the same thickness. Metallocene LLDPE (mLLDPE) is the premium end. Bio-based and recycled-feed PE use the same reactors with different ethylene or mass-balance feed.

#### Routes compared

| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| **High-pressure LDPE (tubular and autoclave)** | about 35-40% of LDPE plus LLDPE supply (indicative) | about 1.01 t ethylene and about 0.8-1.1 MWh electricity per t (indicative) | typical tubular line 300-400 kt/yr (indicative) | over 99% of ethylene ends up in polymer after recycle (indicative) | small wax and purge streams | ethylene cost plus about $150-250/t conversion (indicative) |
| **Gas-phase LLDPE (e.g. Unipol, Spherilene)** | about 40% of LDPE plus LLDPE supply (indicative) | about 0.92 t ethylene, 0.08-0.10 t butene or hexene, about 0.4-0.5 MWh per t (indicative) | 300-650 kt/yr per line (indicative) | about 99% (indicative) | vent gas recovered | ethylene and comonomer cost plus about $80-150/t conversion (indicative) |
| **Solution LLDPE (including octene and metallocene grades)** | about 20-25% (indicative) | about 0.88-0.92 t ethylene and 0.08-0.12 t octene; more steam than gas phase (indicative) | 200-500 kt/yr (indicative) | about 99% (indicative) | solvent recycled | higher than gas phase; premium grades sell above commodity LLDPE (indicative) |
| **Bio-based and circular-feed PE** | well under 1% (indicative) | about 1.7 t ethanol per t ethylene for bio-PE (ethylene tile) | Braskem Triunfo about 260 kt/yr (indicative) | as fossil PE | as fossil PE | bio-PE about 30-50% above fossil PE (indicative) |

#### How each route works
**High-pressure LDPE (tubular and autoclave)**

Ethylene is compressed to about 1,500-3,000 bar and polymerised with peroxide or oxygen initiators at 150-300°C. Conversion per pass is only 20-35%, so large hypercompressors recycle unreacted gas. Autoclaves make coating and EVA grades; tubular reactors make film grades at larger scale.

Unique clarity and melt strength, but power-hungry and capital-intensive; little new capacity outside China (Argus 2025).
 indicative (industry standard); Argus Polyethylene Outlook, Sep 2025 **Gas-phase LLDPE (e.g. Unipol, Spherilene)**

Ethylene and comonomer are polymerised in a fluidised bed at about 20-25 bar and 80-100°C over Ziegler-Natta, chromium or metallocene catalysts. Many lines are swing plants that make either LLDPE or HDPE.

Lowest-cost, flexible swing process; butene grades are commodity, hexene and metallocene grades earn premiums.
 indicative (industry standard) **Solution LLDPE (including octene and metallocene grades)**

Ethylene and octene-1 or hexene-1 are polymerised in a hydrocarbon solvent at 150-250°C with metallocene or constrained-geometry catalysts, then the solvent is flashed off. Short residence time allows fast grade changes and very tough, clear films.

Best performance for thin, strong films and mono-material recyclable packs; fewer licensors and higher energy use.
 indicative (industry standard) **Bio-based and circular-feed PE**

Ethylene from sugarcane ethanol (Braskem) or cracker feed from pyrolysis oil or bio-naphtha is polymerised in standard plants; circular feed is allocated by ISCC Plus mass balance.

Drop-in for converters and recyclable with fossil PE, but costly and supply-limited.
 ethylene tile; 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/polyethylene/index.md)
- [Overview](https://www.materialinsights.org/chemicals/polyethylene/overview/index.md)
- [Correlation](https://www.materialinsights.org/chemicals/polyethylene/correlation/index.md)
- [Production](https://www.materialinsights.org/chemicals/polyethylene/production/index.md)
- [Feedstocks](https://www.materialinsights.org/chemicals/polyethylene/feedstocks/index.md)
- [Cycles](https://www.materialinsights.org/chemicals/polyethylene/cycles/index.md)
- [Trading](https://www.materialinsights.org/chemicals/polyethylene/trading/index.md)
- [Movement](https://www.materialinsights.org/chemicals/polyethylene/movement/index.md)
- [Regulation](https://www.materialinsights.org/chemicals/polyethylene/regulation/index.md)
- [Characteristics](https://www.materialinsights.org/chemicals/polyethylene/characteristics/index.md)
- [Emissions](https://www.materialinsights.org/chemicals/polyethylene/emissions/index.md)
- [Relationships](https://www.materialinsights.org/chemicals/polyethylene/links/index.md)