Polyethylene (LDPE, LLDPE): Characteristics
Density and melt flow: how converters choose a grade
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Converters buy PE by density, melt flow index and comonomer type. These set how a resin runs on a film line and how tough, clear or sealable the film is. Additives (slip, antiblock, UV) and the catalyst family (Ziegler-Natta versus metallocene) also matter, and so does contamination for recycled grades.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Density | LDPE about 0.915-0.935 g/cm3; LLDPE about 0.915-0.940 g/cm3 | Lower density means softer, tougher film; higher density means stiffer film. | standard polymer data (indicative) |
| Melt flow index (190°C, 2.16 kg) | film grades about 0.5-4 g/10 min; coating grades 4-10 (indicative) | Sets processability and output rate on blown-film and coating lines. | industry standard (indicative) |
| Comonomer type | butene (C4), hexene (C6) or octene (C8) | C6, C8 and metallocene grades give higher dart impact and tear strength and sell at a premium. | industry standard (indicative) |
| Melting point | LDPE about 105-115°C; LLDPE about 120-125°C | Determines sealing temperature and heat resistance. | standard polymer data |
| Carbon content | about 86% by mass | Sets CO2 released if burnt: about 3.1 t CO2 per t. | stoichiometric |
Commercial grades
- LDPE film (general packaging, shrink film)
- LDPE extrusion coating (autoclave)
- LLDPE C4 film (commodity)
- LLDPE C6/C8 and mLLDPE film (premium, thin, strong)
- LLDPE rotomoulding powder (water tanks)
- EVA copolymers (solar encapsulant, foams)
- XLPE cable compounds
- PCR LDPE/LLDPE recyclate (non-food film, bin liners)