Materials · high-density polyethylene

HDPE cores: high-density polyethylene, virgin and recycled

ROLL Lab · updated 24 October 2026 · sources at the bottom of the page

What HDPE is

High-density polyethylene is the polyolefin of water and gas pipes, drums and crates. Its density is 0.94–0.97 g/cm³, so it floats, and its glass transition is very low, around −110 °C: at room temperature and in the cold it is far from brittle. It extrudes easily and accepts recycled material well.

Strengths

• Toughness: it resists impact even at −30 °C and below. An HDPE core dropped off a lorry in winter usually dents but does not split.
• Sunlight: with about 2–2.5% well-dispersed carbon black, HDPE resists UV for years. It is the same principle as polyethylene water pipes laid outdoors.
• Moisture and chemicals: it absorbs no water and resists fertilisers, crop protection products and many chemicals.
• Recycling: it goes into the established polyolefin stream; recycled HDPE is widely available.
• Weight: at the same size about 1.14 times a cardboard core (Fiaptech technical documentation, a company with corporate ties to ROLL).

Limits

• Stiffness: short-term modulus 0.8–1.4 GPa, the lowest of the three main polymers. In Fiaptech documentation the 3% strength of an HDPE core is only 1.08 times that of cardboard (1.01 for recycled).
• Creep and heat: two-year creep ratio up to 4 (EN 13476-2 for PE pipes), HDT at 1.8 MPa of 45–60 °C. Under heavy rolls and in the heat the bore closes more than with PVC and PP.
• Reuse: the same documentation reports the lowest minimum cycles (more than 3 for virgin, more than 5 for recycled). The figure is indicative and depends on use.
• Bending in the sun: recycled HDPE cores stored in the sun tend to bend more than the others.
• Stress cracking: under stress and in contact with surfactants (detergents, soaps, some oils) HDPE can crack slowly, a phenomenon called environmental stress cracking. It matters for returnable cores washed with detergents: ask for a grade with good resistance, measured with the FNCT test (ISO 16770), and rinse well.

Virgin or recycled

Source: Fiaptech technical documentation, Smart Book “Which core?”. Recycled HDPE is a practical route to the recycled content required by the PPWR, and to the 30% threshold of the UK Plastic Packaging Tax, as long as it is post-consumer and traced (how recycled content is documented). Recyclate quality varies a lot: rigid packaging (bottles, drums) gives more consistent compounds than mixed sources.

Outdoors and agricultural film

Black HDPE is the typical choice for rolls that stay outdoors: greenhouse, mulch and silage film, nets, geotextiles. Carbon black protects against UV; toughness protects against knocks in the field and on farm vehicles. The point to check is temperature: a black core in summer sun gets much hotter than the air. If the roll is heavy, you need a generous wall, or a core in a stiffer material kept out of the sun. Cores for agricultural film.

Try it with your own data below; method, assumptions and sources are on the dedicated page: the minimum wall estimate with creep.

Walls and sizes: how much thickness you need

With a modulus about three times lower than PVC, HDPE needs more wall to resist buckling under roll pressure. ROLL Lab orders of magnitude, with stated assumptions and for a free ring at 23 °C, give a 3" core with a 10 mm wall a long-term pressure capacity of about 17 bar, against about 60 for PVC and 25 for PP. At 6" the gap widens: walls of 15 mm or more are needed even for moderate pressures.

In practice HDPE works well for light or medium rolls, for small diameters, and where toughness and UV resistance matter more than stiffness. For heavy rolls of elastic film, start from PVC or filled PP. The formulas and the full table.

HDPE and PPWR

HDPE has two advantages under the new European obligations. First: post-consumer recycled HDPE, from bottles, drums and crates, is available from established chains and can help reach the 35% required from 2030 for “other plastic packaging”. Second: as a mono-material polyolefin it starts from a good position for the recyclability criteria of Art. 6. Still to be checked are recyclate consistency and, for black cores, how well sorting plants can detect them. PPWR and plastic cores.

Cutting

Like PP, HDPE cuts best on a lathe: clean edge, few strings. A saw tends to leave fibrous burrs; a crush knife can squash the soft edge. Fiaptech documentation gives the lathe the top score for PE. Cutting plastic cores.

End of life

A clean HDPE core is plastic packaging waste (code 15 01 02) and is recycled with the polyolefins. Black cores are harder to detect with the near-infrared sensors of sorting plants: in industrial streams, collected separately, the problem is smaller. Recycling plastic cores.

Frequently asked questions

Further reading

Sources

1. Fiaptech technical documentation, Smart Book “Which core?” (a company with corporate ties to ROLL)
2. SpecialChem, Heat Deflection Temperature of Plastics (HDPE)
3. EN 13476-2, creep ratio according to EN ISO 9967
4. EN 12201-1, polyethylene pipes for water supply (carbon black content as a UV stabilisation reference)
5. Regulation (EU) 2025/40 (PPWR), Art. 7, EUR-Lex
6. ROLL Lab analysis
7. ISO 16770, Full Notch Creep Test (environmental stress cracking resistance of polyethylene)