Forming
Guide the tape through a forming die so the overlap is consistent (usually 3 – 6 mm). An uneven overlap is the most common cause of seal failure.
Cable materials guide
Aluminium-Plastic Composite Strip for Cables and Optical Cables
Aluminium-plastic composite strip is soft aluminium tape coated on one or both sides with polyethylene or an ethylene copolymer. Cable makers fold it lengthwise around the cable core, where it forms a moisture barrier and an electrical screen, and the plastic layer heat-seals to the overlap and to the outer sheath. This guide explains the tape types, dimensions, performance tests and how to specify the strip; Metline supplies it in pads and slit coils to cable plants worldwide.
- Aluminium core
- 0.10, 0.15, 0.20 mm, O temper
- Coating
- PE or EAA copolymer, one or two sides
- Types
- YL · YLY · EL · ELE
- Use
- Moisture barrier and screen
What the composite strip does in a cable
Water is the main enemy of telecom and fibre-optic cables. Moisture that diffuses through a polyethylene sheath can raise attenuation in copper pairs and, over years, weaken optical fibres. A thin, continuous metal layer stops that diffusion almost completely, and aluminium is the cheapest, lightest metal that can be formed into such a layer at line speed.
In the classic "APL" or "laminated aluminium polyethylene" sheath, the tape is longitudinally applied over the core with an overlap of a few millimetres. As the hot polyethylene jacket is extruded over it, the plastic coating on the tape melts and bonds to the jacket and to itself at the overlap. The result is a sealed, bonded sheath that resists water, bends with the cable and does not crack.
Besides blocking moisture, the aluminium layer acts as an electrostatic screen against external interference, and in metallic cables it can serve as a continuity or earthing path. In some designs the tape also gives modest protection against rodents and mechanical damage, although steel tape is used where real armouring is required.
Single-sided and double-sided types
Telecommunications industry standards classify the strip by coating material and by whether one or both sides are coated. The type codes below are widely used in tender documents for optical cable materials.
| Type code | Coating | Sides coated | When it is chosen |
|---|---|---|---|
| YL | Polyethylene | One | Sheaths where only the outer jacket bonds to the tape |
| YLY | Polyethylene | Two | Overlap sealed tape-to-tape and bonded to the jacket |
| EL | Ethylene copolymer (e.g. EAA) | One | Stronger adhesion to the metal and to PE jackets |
| ELE | Ethylene copolymer (e.g. EAA) | Two | Most common for fibre cables needing a fully bonded, sealed sheath |
Copolymer coatings such as ethylene acrylic acid (EAA) contain polar groups that bond chemically to the aluminium oxide surface, so they hold better after heat ageing and immersion than plain polyethylene. That is why EL and ELE types dominate modern optical cable production. The standard colours are natural (translucent) and blue, which helps operators tell coated and uncoated sides apart.
The aluminium strip inside the tape
The metal layer is a thin, fully annealed (O temper) aluminium strip, usually from the 1xxx series such as 1050 or 1060, or 8xxx foil alloys where higher strength at thin gauges is wanted. Annealing matters: the tape must fold around the core and corrugate without cracking, and residual rolling oils must be removed so the coating adheres.
| Property | Requirement or typical value | Why it matters |
|---|---|---|
| Nominal metal thickness | 0.10, 0.15 or 0.20 mm | Thicker metal gives better barrier and screen but a stiffer cable |
| Temper | O (annealed) | Ductility for folding and corrugation |
| Tensile strength of composite strip | ≥ 54 MPa | Survives tension on the sheathing line |
| Elongation | ≥ 15 % | Bends with the cable without tearing |
| Surface | Clean, degreased, often chemically pre-treated | Needed for a strong coating bond |
| Density of aluminium | 2.70 g/cm³ | Basis for weight and length calculations |
Values in this table follow the requirements commonly specified for telecom composite tape. The actual limits on your order are those of the agreed standard or specification.
Thickness, width and length
Tape is supplied either as wide "uncut" master rolls for the cable maker to slit, or as narrow slit pads already cut to the width needed for a given cable diameter. A typical slit width is the cable core circumference plus the overlap.
| Aluminium thickness (mm) | Single-sided composite (mm) | Double-sided composite (mm) |
|---|---|---|
| 0.10 | 0.16 ± 0.021 | 0.22 ± 0.034 |
| 0.15 | 0.21 ± 0.025 | 0.27 ± 0.038 |
| 0.20 | 0.26 ± 0.029 | 0.32 ± 0.042 |
Other dimensions
- Coating layer
- About 0.058 ± 0.013 mm per coated side
- Uncut widths
- 290, 400 and 600 mm (± 5 mm) are common master widths
- Slit widths
- To cable design, typically ± 0.5 mm
- Lengths per slit pad
- Common lengths of about 1,020 – 2,600 m, or to order
- Core
- Paper or plastic core sized to the payoff on the sheathing line
A quick check on pad length: a 30 mm wide, 0.15 mm aluminium tape with two 0.058 mm coatings weighs roughly 15 – 16 g per metre, so a 2,000 m pad is about 30 – 32 kg. Always confirm against the payoff capacity of your line.
Performance requirements and test methods
| Test | Typical requirement | What it proves |
|---|---|---|
| Peel strength, aluminium to coating | ≥ 6.13 N/cm | The coating will not lift off during forming |
| Heat-seal strength (coating to coating) | ≥ 17.5 N/cm | The overlap stays sealed |
| Shear of heat-sealed zone | Tape or bond to metal fails before the seal shears | The seal is stronger than the rest of the tape |
| Water resistance (68 ± 1 °C, 168 h) | Peel strength still ≥ 6.13 N/cm | Adhesion survives long-term moisture |
| Resistance to filling compound (68 ± 1 °C, 168 h) | No delamination | Compatible with cable jelly and water-blocking compounds |
| Alkali corrosion resistance (NaOH solution) | Rated after long immersion; no significant attack | Coating protects the metal from alkaline groundwater |
| Dielectric strength | Single-sided 1 kV d.c., double-sided 2 kV d.c., 1 min, no breakdown | The coating is continuous with no pinholes |
ASTM B736 covers aluminium and aluminium-alloy cable shielding stock, including coated strip, and is often cited for the test methods. In Chinese telecom tenders the YD/T 723 series is referenced; IEC cable standards set the sheath requirements that the tape helps meet. Ask for test results with each lot, not just a type certificate.
Winding, joints and packing
- Pads must be wound tightly and evenly so they do not telescope or collapse when stood on edge
- Only one strip is wound on each core; two tapes on one core are not acceptable
- Overlapping joints are not allowed within a pad; butt-welded joints are normally permitted and marked
- Edges must be clean and free of burrs, which can puncture the jacket or cause poor sealing
- Pads are wrapped in moisture-barrier film with desiccant and packed on pallets or in wooden cases
- Store dry and below about 40 °C; use first-in, first-out, as the copolymer can absorb moisture over time
Practical notes for the sheathing line
Corrugation
Corrugated tape improves flexibility and crush resistance on larger cables. Use annealed metal; hard tape cracks at the corrugation roots.
Temperature
The jacket melt temperature must be high enough to activate the copolymer at the overlap. Too cool gives weak bonding; too hot can thin the coating.
Earthing
Where the tape is used as a screen, remove the coating at terminations so the metal can be bonded to earth.
Storage
Condition pads to line temperature before use to avoid condensation on the tape.
Inspection
Check peel and seal strength from the finished cable regularly, not only from incoming tape.
Aluminium composite tape vs alternatives
| Material | Moisture barrier | Screening | Mechanical protection | Weight |
|---|---|---|---|---|
| Aluminium-plastic composite tape | Excellent | Good | Low | Low |
| Steel-plastic composite tape | Excellent | Good, plus magnetic | Good (rodent and crush) | Higher |
| Aluminium-polyester foil (Al/PET) | Good | Very good (thin foil) | Very low | Very low |
| Plain polyethylene jacket only | Poor over decades | None | Low | Lowest |
Many outdoor fibre cables use aluminium tape inside and a steel tape armour outside, or a single steel tape where rodent protection matters more than weight. For thin screening foils in data cables, see our page on laminated aluminium foil.
How to order
- SpecifyType code, aluminium thickness, coating colour, slit width or uncut width, pad length, core size and the governing standard.
- QuoteWe confirm availability, test data, packing and delivery terms (EXW, FOB, CIF or DAP).
- TrialTrial pads can be arranged for line qualification before volume orders.
- ShipMoisture-protected packing on pallets or cases, with a certificate of conformity and test report for each lot.
References and standards
- ASTM B736 – Aluminum, Aluminum Alloy and Aluminum-Clad Steel Cable Shielding Stock
- YD/T 723.2 – Metallic composite tapes for communication cables and optical cables: aluminium tape
- IEC 60794 – Optical fibre cables (generic and sectional specifications)
- EN 573-3 – Chemical composition and form of wrought aluminium products
Aluminium-plastic composite tape: FAQ
What is the difference between YLY and ELE tape?
Both are coated on two sides. YLY uses polyethylene, while ELE uses an ethylene copolymer such as EAA that bonds more strongly to aluminium and keeps its adhesion better after heat and water ageing. ELE is the usual choice for bonded optical cable sheaths.
Which aluminium thickness should I use?
0.15 mm is the most common choice for fibre and telecom cables. Use 0.10 mm for small, flexible cables and 0.20 mm where a stronger barrier or better corrugation strength is needed.
Why is the coating blue or natural?
Those are the standard colours. Colour helps identify the coated side and the tape type on the line and in the finished cable. Other colours may be possible by agreement.
Can the aluminium layer earth the cable?
Yes, it can serve as a screen or continuity conductor, but the coating is an insulator, so it must be removed at terminations to make the earth connection.
Are welded joints allowed in a pad?
Butt-welded joints are normally accepted if they are marked and keep full width. Overlapping joints are not accepted because they jam forming dies and leave gaps in the seal.
What aluminium (aluminum) alloy is used?
Annealed 1xxx-series aluminium such as 1050 or 1060 is typical, with 8xxx foil alloys used in some products. The key requirement is O temper with a clean, pre-treated surface.
Qualifying a new tape source?
Send your cable design and tape specification. Metline will reply with matching composite strip, test data and delivery options.
