What Is Polyethylene (PE)? The AYPE, YYPE and LLDPE Family

Polyethylene (PE) is obtained by polymerizing the monomer ethylene and is the plastic produced in the largest volume worldwide. Although it looks like a single material, the chain structure (degree of branching) can vary greatly depending on the production method — producing several material families under one name that behave quite differently from one another.

The key variable behind this difference is density: the less branched the chains and the more tightly they pack together, the higher the density (see the related article 'What Is Density').

Produced by free-radical polymerization under high pressure. This method causes both long and short branching along the main chain — this branching prevents tight chain packing, resulting in low density (approximately 0.910-0.940 g/cm³) and high flexibility.

Typical uses: shopping bags, shrink film, lamination film, flexible packaging — applications requiring high flexibility and good optics (clarity/transparency).

Produced at low pressure using coordination catalysts (Ziegler-Natta, Phillips or metallocene). Branching is minimal, chains are nearly linear and pack tightly — giving higher density (approximately 0.941-0.965 g/cm³), greater stiffness and mechanical strength.

Typical uses: drinking water/natural gas pipes, rigid containers and drums, crates, large-volume tanks — applications requiring rigidity and structural strength.

Has a similar density range to AYPE but a different production method: ethylene is copolymerized with an alpha-olefin comonomer (butene, hexene or octene) using coordination catalysts. The result is a more linear chain structure with short side branches but no long branching.

Compared with AYPE, this structure provides higher tensile strength and better puncture and tear resistance — allowing thinner (less material) film to be produced for the same performance. See the related article for details.