Glossary · terms, abbreviations, standards

Plastic core glossary

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

A

ABS: Acrylonitrile butadiene styrene: a rigid, tough thermoplastic with precise dimensions. Used for small, precise reusable cores and for plugs.

Air shaft (expanding shaft): Machine shaft that, inflated with air, pushes lugs or leaves against the inside of the core and locks it. Sometimes called a mandrel: not to be confused with the core.

Antistatic core: Core with antistatic additives or conductive fillers, for electronics lines and cleanrooms where static charge attracts dust or damages components. Classified by surface resistance (IEC 61340-5-3).

B

Bow: Maximum deviation of the core axis from a straight line, expressed in mm per metre of length.

Buckling (wall instability): Collapse of a ring under external pressure that happens before yield. The critical pressure grows with the cube of the wall-to-diameter ratio.

C

CaCO₃ (calcium carbonate): Mineral filler added to PP to increase stiffness and reduce cost. At about 15% the compound becomes denser than water.

Carbon black: Black carbon pigment that protects polyolefins from UV rays. Used in HDPE for cores and pipes intended for outdoor use.

Circular saw: Cutting method with a toothed blade that removes a strip of material. Gives the best edge on rigid PVC; produces chips.

Compound: A ready-to-process blend: polymer plus additives, fillers, stabilisers, pigments and sometimes recyclate. The properties of a core depend on the compound, not only on the polymer.

CONAI: Italian national packaging consortium. Its 2013 circular on tubes and rolls treats cores with wound material as packaging, except machinery parts.

Contact-sensitive packaging: PPWR category for packaging of products such as food, medicines and medical devices, with lower recycled content percentages (Art. 7). Defined in Art. 3.

Core: The tube that a roll of film, paper, fabric or tape is wound on. Shop-floor synonyms: tube, sometimes mandrel. Italian anima, French mandrin, Spanish mandril, German Wickelhülse.

Core plug: Accessory that fits into the end of a core to protect its bore, or to lift or suspend the roll.

Cradle: Shaped support on which a roll lies, to spread the load and stop it rolling.

Creep: Slow deformation of a material under constant load. In plastic cores it makes the bore close in the days and weeks after winding.

Creep ratio: Ratio of long-term to initial deflection under constant load (EN ISO 9967). EN 13476 allows up to 2.5 for PVC-U and 4 for PP and PE at two years.

Crush knife: Cutting method with a plain disc that parts the rotating tube without removing material. Common for cardboard, less suited to rigid plastic.

D

Density: Mass per unit volume, in g/cm³. It decides the weight of the core and how it behaves in sink-float separation: PP and PE float, PVC sinks.

E

End wall (endwall): Disc or plate wider than the roll, fixed to its ends, that protects the edges and keeps the roll raised. Also called a reel end or flange.

End-of-roll residue: Material left on the core at the end of a roll: splice reserve, end of batch, defects. It turns a clean core into mixed waste.

Environmental stress cracking (ESC): Slow cracking of a polyolefin, especially HDPE, under stress and in contact with surfactants such as detergents and soaps. Assessed with the FNCT test (ISO 16770).

EPR: Extended producer responsibility: the obligation for those placing packaging on the market to fund its end-of-life management. The PPWR extends it to all packaging (Art. 45); the UK runs its own pEPR scheme.

Extrusion: Process in which molten polymer passes through an annular die and is sized, cooled and cut. The main method for making plastic cores.

F

FCM (food contact materials): Materials and articles intended to come into contact with food. General framework in Regulation (EC) 1935/2004; for plastics, Regulation (EU) 10/2011.

Flange: See end wall. A disc or plate at the ends of the roll that protects its edges and keeps it raised.

Friction shaft: Shaft, also called differential, that transmits a set torque to each side-by-side core through rings with balls or rollers. It needs cores with constant lengths and diameters.

G

Glass transition: Temperature above which an amorphous polymer changes from rigid to rubbery. For PVC it is around 80 °C, for PP around 0 °C.

H

HDPE (PE-HD): High-density polyethylene: tough even in the cold, UV resistant with carbon black, less stiff than PVC and PP. Identification code 2.

HDT: Heat deflection temperature: the temperature at which a loaded specimen (0.46 or 1.8 MPa) deflects by a set amount. It indicates the thermal limit under load.

I

Inside diameter (ID): The diameter of the core bore, which must fit the shaft. The most common sizes are 76 mm (3") and 152 mm (6").

ISO 11093-9: Standard on the flat crush resistance of paper cores: measures the first force peak on a 100 mm specimen.

ISO 13542: Standard on internal diameters and tolerances of cores for paper and board reels. The most used reference for plastic cores too.

ISO 9969: Standard on the ring stiffness of thermoplastic pipes: measures the force that deflects the pipe by 3% between parallel plates, at set speeds.

L

Lamé formula: Thick-walled tube formula that gives the stress in the wall under pressure. Used to check crushing of the core material.

Lathe (parting off): Cutting method with a fixed tool on the rotating tube. Gives the cleanest, squarest face; the best for PP and PE.

List of Waste code (EWC): Code from the European List of Waste, also used in the UK. Clean plastic cores normally use 15 01 02; with residual material, 15 01 06.

M

Maximum load: The highest force reached when crushing a core specimen between two plates. For plastic, which has no clear peak, it is weakly linked to real use.

Modulus of elasticity: Measure of a material’s stiffness, in GPa. Rigid PVC has about twice the modulus of PP and HDPE.

N

NIAS: Non-intentionally added substances: impurities and degradation products that can migrate from a plastic. Assessed for food contact.

O

Ovality: Difference between two perpendicular diameters of the core. ISO 13542 allows at most 1.5 mm on the inside diameter from Ø 70 upwards.

P

Parent reel: Wide reel produced by the extrusion line or paper machine, then slit into narrower rolls. Often uses 6" cores.

Plain shaft: Shaft without expansion that enters the core with little play. It needs tight inside diameter tolerances.

Plastic Packaging Tax (PPT): UK tax, in force since April 2022, on plastic packaging components made in or imported into the UK with less than 30% recycled plastic. Charged per tonne above a 10-tonne annual threshold.

Post-consumer recycled content: Plastic recovered from waste after use by the end user. The only recyclate that counts for the obligations of PPWR Art. 7.

PP: Polypropylene: the lightest plastic for cores, handles higher temperatures than PVC under light loads. Homopolymer is stiff, copolymer tougher. Code 5.

PPWR: Regulation (EU) 2025/40 on packaging and packaging waste, applicable from 12 August 2026. It sets recyclability, recycled content, reuse and labelling rules.

PS: Polystyrene: stiff and cheap, but brittle on impact and in the cold. Used for small cores, plugs and end walls. Code 6.

PVC-U (rigid PVC): Polyvinyl chloride without plasticisers: the stiffest of the common core polymers, dislikes heat and must be recycled separately. Code 3.

R

Radial pressure: Pressure that the wound wraps exert on the core. In the literature it ranges from about 5 to over 100 bar depending on material, tension and time.

Recyclability grade: A, B or C rating introduced by the PPWR (Art. 6, Annex II): at least 95%, 80% and 70% recyclability by weight. From 2038 at least grade B is required.

Reusable packaging: Packaging that meets the requirements of PPWR Art. 11: designed for many rotations, emptied without damage, reconditionable and recyclable at end of life.

Ribbed bore: Inside surface of a core with longitudinal ribs that improve grip on the shaft. Also called grooved, serrated or knurled. Not a standard term: specify number, depth and profile of the ribs.

Ring stiffness: Resistance of a ring to diametral deflection, in kN/m², measured to ISO 9969. Linked to the critical buckling pressure of the core.

Rotation: In the PPWR, the full cycle of reusable packaging from being placed on the market with the product to being ready for reuse.

S

Step gauge: Tool with stepped diameters for a quick go/no-go check of a core’s inside diameter.

T

TIR: Total indicated runout: the swing read on a dial indicator while the core turns. It sums up ovality, eccentricity and bow.

Transport packaging: Packaging designed to handle and transport products without damage (PPWR, Art. 3). The harmonised composition label does not apply to it, except for e-commerce.

W

Wedge (chock): Block placed against a lying roll to stop it rolling during transport and storage.

Frequently asked questions

Further reading

Sources

1. ISO 13542, ISO 9969, EN 13476
2. Regulation (EU) 2025/40 (PPWR), Art. 3
3. ROLL Lab analysis