Polyethylene (PE) is the most produced plastic in the world. Yet "polyethylene" is not a single material; it is a family whose behavior depends on chain structure and density.
HDPE (High-Density PE)
Its chains have little branching and its density is roughly 0.94–0.97 g/cm³. It is stiffer, stronger and resistant to chemicals. It is used in pipes, drums, bottles, crates, caps and geomembranes.
LDPE (Low-Density PE)
Its long-chain branching makes it flexible and nearly transparent, with a density of roughly 0.91–0.94 g/cm³. It is common in film, bags, wrap and squeezable packaging and processes well in extrusion.
LLDPE (Linear Low-Density PE)
It has a linear structure with short branches. Compared with LDPE it offers higher tear and puncture resistance, allowing thinner film gauges. It is preferred for stretch film, agricultural film and heavy-duty bags. Powder PE grades used in rotational molding mostly come from this family as well.
What to look at when choosing
- Melt flow index (MFI): Flow suited to the processing method
- Density: The balance between stiffness and flexibility
- Additives: UV stabilizers, antioxidants, color masterbatch