Technical guide by Plasticalia Chemical
HDPE, LDPE, LLDPE and MDPE: differences and uses of polyethylene
HDPE, LDPE, LLDPE and MDPE are all polyethylene, but they behave very differently. We explain how they differ and which one suits each application.
The key: density and the shape of the chains
All polyethylenes are made from ethylene. What changes is how their chains are arranged: the more linear and ordered they are, the more tightly they pack, the higher the density of the plastic and the more rigid it is. The more branching, the lower the density and the greater the flexibility.
| Type | Density (g/cm³) | What it is like | Typical uses |
|---|---|---|---|
| LDPE (PEBD) · low density | 0.910–0.930 | Flexible, transparent, very easy to process | Film, bags, shrink and agricultural film, coatings |
| LLDPE (PELBD) · linear low density | 0.915–0.935 | Flexible but far more resistant to puncture and tearing | Stretch film, industrial bags and sacks, blends with LDPE |
| MDPE (PEMD) · medium density | 0.926–0.940 | Balance between rigidity and toughness | Rotationally moulded tanks, pipes, film with body |
| HDPE (PEAD) · high density | 0.941–0.965 | Rigid, highly resistant to impact and chemicals | Bottles and jerrycans, crates, caps, thin bags, pipes |
LDPE versus LLDPE: the most common question in film
Their densities are similar, but LDPE has long branches that make it very easy to blow into film and give it gloss and transparency, whereas LLDPE, being linear, is considerably stronger: it allows film thickness to be reduced while keeping its strength.
That is why it is very common to blend them: LLDPE contributes strength and LDPE contributes bubble stability and gloss. The ratio depends on what the film is used for.
When to choose HDPE
When you need rigidity and chemical resistance: detergent packaging, jerrycans, drums, crates, caps or very thin T-shirt bags. Within HDPE, the grade varies greatly depending on the process (blow moulding, film, injection moulding or monofilament): check its melt flow index and, for chemicals, its stress crack resistance (ESCR).
When to choose MDPE
When HDPE is too rigid and LDPE falls short: rotationally moulded tanks and parts, pipes and film with more body.
Spanish and English acronyms
On technical data sheets you will see the English acronyms (HDPE, LDPE, LLDPE, MDPE); in Spain, PEAD, PEBD, PELBD and PEMD are also used. They mean the same thing.
See all the grades in our catalogue: HDPE, LDPE, LLDPE and MDPE. Questions about your application? Write to us.