# How strong are cable ties (or tyraps)?

*The box says 22.2 kg. Many buyers read that as the weight they can hang from it – and that is exactly where things go wrong. Those 22.2 kg are a breaking value measured under laboratory conditions, not a working load for a cable run that hangs outdoors for five years. This article explains what the tensile strength of a cable tie really tells you, how that figure is established, how much margin you should allow in practice, and which width belongs to which bundle. Since 2007, we have been the go-to wholesaler for cable ties, which means we see exactly where things go wrong in the field: almost never because the tie was too light, almost always because the number on the box was read the wrong way.*

## What does the tensile strength on the packaging actually mean?

The figure you find on the packaging and on the product pages of our [cable ties](en/closure-materials/cable-ties) is the **minimum loop tensile strength**. That is the force at which a closed loop fails – not the force at which it still works safely. The distinction sounds academic, but in practice it decides whether a bundle is still hanging after three years or lying on the floor.

### Tensile strength is a breaking value, not a working load

At the stated figure the cable tie gives way: the strap tears, or the pawl in the head releases. You never design with that number. As with a lifting sling or a chain, you work with a safety factor – more on that below. One thing worth remembering: the manufacturer states a *minimum*. A good polyamide 6.6 tie usually tests slightly above what its type number promises, but you calculate with the minimum, because that is the value being guaranteed.

### How is tensile strength measured?

The measurement is taken with a closed loop, not with a straight strap. The tie is placed around two mandrels, clamped in a tensile tester and slowly pulled apart until it fails. That choice is deliberate: in real use the strap is always in a loop as well, and the transition into the head is precisely where stress concentrates.

Testing takes place at roughly 23 °C and average humidity. That is not a detail, because polyamide behaves differently in frost, heat and dry air. In a cold store or on a rooftop in summer, the same tie will not reach the same value – see the section on environmental influences below.

### Why is the value given in kilograms rather than newtons?

Strictly speaking, tensile strength is a force, and forces are expressed in newtons. The industry sticks to kilograms because buyers and installers calculate faster in them: a bundle of ten metres of cable simply weighs a certain number of kilos. Converting is easy – multiply the kilograms by 9.81 to get the value in newtons. A 22.2 kg tie is therefore good for roughly 218 N. The table below shows both figures side by side.

## Tensile strength by width: the common classification

Width and thickness determine strength, not length. A 200 mm tie and a 500 mm tie of the same width have identical tensile strength – the longer version simply spans a thicker bundle. This is the most common misconception when ordering: longer is not stronger.

WidthTensile strengthConvertedTypical application2.5 mm8.1 kgapprox. 80 NThin signal and data cables, labels, light bundles3.6 mm18.2 kgapprox. 180 NStandard indoor installation work, patch cables, assembly4.8 mm22.2 kgapprox. 218 NThe workhorse size: cable bundles, hoses, general fastening7.6 mm46 – 54.4 kgapprox. 450 – 535 NHeavier bundles, outdoor work, temporary structures9.0 mm79.4 kgapprox. 780 NThick cable runs, pipework, construction sites12 – 13 mm114 kgapprox. 1,120 NHeavy industrial bundling, fencing, scaffold sheetingStainless steel bandup to 230 kgapprox. 2,250 NOffshore, chemical plants, high temperatures, fire-safe installationsThe exact figure is always listed with the individual article; between manufacturers there can be a few kilos of difference at the same width. Use the table to choose the right order of magnitude, then check the specification on the product page.

### What safety margin should you allow?

A workable rule of thumb from installation practice: load a cable tie permanently to no more than a third of its stated tensile strength, and to no more than a quarter where vibration, fluctuating loads or outdoor exposure are involved. A 22.2 kg tie therefore comfortably carries a seven-kilo bundle indoors, or five kilos on a machine that vibrates.

That margin covers three things at once: the ageing of the material, the temperature and humidity swings the tie actually encounters, and the fact that loads are rarely evenly distributed. If a genuine load hangs from it – rather than a bundle simply being held in place – deliberately size up, or use a solution designed for the job, such as our [fastening materials](en/fastening-materials) or [strapping materials](en/strapping-materials).

## Why a cable tie rarely fails at its breaking value in practice

Anyone examining a failed cable tie almost never finds a strap that has torn cleanly in the middle through overload. Most failures have a different cause – and every one of those causes is avoidable.

### The bundle is often the weak point, not the tie

If the tie runs over a sharp sheet-metal edge, a bolt head or a burr, the entire load concentrates on a few millimetres of strap. There it fails well below the stated figure, because the notch acts as a fracture line. The answer is not a heavier tie but removing the sharp edge: a piece of [heat shrink tubing](en/closure-materials/heat-shrink-tubing) or [spiral wrapping band](en/closure-materials/spiral-wrapping-bands) underneath does more for service life than going two sizes up.

### Over-tightening reduces strength

A cable tie pulled up to maximum force with a tool sits under permanent pre-tension. That pre-tension adds to every load that follows, and concentrates precisely at the head – the point with the smallest cross-section. An over-tightened strap also deforms the cable sheath underneath, which leads to insulation damage over time.

If you work in volume, use a tool with adjustable tension from our range of [cable tie pliers](en/closure-materials/cable-ties/cable-ties_pliers). It tightens every tie to the same preset force and cuts the tail off flush. That last point is not a luxury: a tail snipped with side cutters leaves a sharp point that engineers cut their hands on.
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### How tight should a cable tie actually be?

Tight enough that the bundle cannot shift, loose enough that you can rotate the strap slightly with one finger. On cables that get warm – power cables, lighting – deliberately leave a little more room: the sheath expands and would otherwise press itself into the strap. On a bundle that vibrates, two ties spaced apart beat one very tight tie.

### Can you link two cable ties to double the strength?

No. Two ties knotted together form a chain, and a chain is exactly as strong as its weakest link – with the added problem that the head of one now cuts into the strap of the other, which lowers strength further. Two ties *side by side* over the same bundle do share the load, but never perfectly evenly; count on roughly one and a half times the value of a single tie, not double. If you need more circumference, choose a longer strap from the [heavy duty cable ties](en/closure-materials/cable-ties/heavy-duty-tyraps).

## What the environment does to tensile strength

The value on the box applies at room temperature and normal humidity. As soon as the tie leaves those conditions, the material behaves differently – sometimes in your favour, more often not.

### Moisture: polyamide behaves like a sponge

Polyamide 6.6 absorbs moisture from the air, up to a few per cent of its own weight. That water settles between the polymer chains and acts as a plasticiser: the strap becomes more flexible and more impact-resistant, but its tensile strength drops. Conversely, a bone-dry tie – straight from a heated store room, or years inside a dry control cabinet – is stronger on paper but brittle: it snaps as you tighten it instead of giving way.

In practical terms: store cable ties in their sealed packaging and away from heating, and expect slightly more resistance when tightening a tie that has just come out of cold, dry storage.

### Temperature: where the limits lie

Standard polyamide 6.6 cable ties work between roughly −40 °C and +80 °C. Within that range they are usable, but not equally strong everywhere: in frost, stiffness increases and elongation drops, so a tie you pull up at minus ten degrees will break sooner than the same tie indoors. That is exactly what [cold-resistant cable ties](en/closure-materials/cable-ties/cold-resistant-tyraps) are for – they keep their flexibility at low temperatures, which makes them indispensable in cold stores and for winter installations outdoors.

At the other end of the scale, [heat-resistant cable ties](en/closure-materials/cable-ties/heat-resistant-cable-ties) run to +115 or +120 °C depending on the version, and meet the UL94 V-2 flammability class. Use them in control cabinets, engine bays and in heating and ventilation installations. If it needs to go hotter still, or fire behaviour is critical, you end up with [stainless steel cable ties](en/closure-materials/cable-ties/stainless-steel-cable-ties).

### Why does a white cable tie snap outdoors while a black one does not?

The difference is not the colour itself but what has been added to the polyamide. UV-resistant cable ties contain a UV stabiliser: an additive that captures incoming UV radiation in the outer layer of the strap and converts it into heat before it can break down the polymer chains. In practice that additive is almost always compounded into the black version – which is why black and outdoor use have become synonymous in this industry. A tie without that stabiliser has no protection at all: UV breaks down the chains, the material lightens in colour, turns brittle and snaps after one season at the first real load.

So the rule is simple: anything hanging outdoors for more than a few months goes black. Our [black cable ties](en/closure-materials/cable-ties/black-tyraps) are UV-resistant as standard; for prolonged full sun there are [extra UV-resistant cable ties](en/closure-materials/cable-ties/extra-uv-resistant-tyraps). [White cable ties](en/closure-materials/cable-ties/white-cable-ties) and [coloured cable ties](en/closure-materials/cable-ties/cable-ties-in-various-colors) are excellent indoors – and particularly valuable there, because they let you colour-code circuits, departments or installation years.

### Chemicals and radiation

Polyamide 6.6 resists diluted acids and oils well, which makes it usable in workshops and machine building. Strong acids, alkalis and prolonged immersion are another matter: there the material loses strength without showing it on the outside. In chemically aggressive or marine environments, choose stainless steel, where the epoxy-coated 316 version goes a step further than 304. Radiation-exposed environments are stainless steel territory too.

## Which cable tie for which load?

With tensile strength as the starting point, the choice usually comes down to three steps: determine the circumference of the bundle, the load, and the environment. Circumference gives you the length, load gives you the width, environment gives you the version.

### Indoors, light to normal bundles

For cable bundles in offices, control cabinets and workshops, 3.6 or 4.8 mm is more than enough. If you work in IT or a data centre, where bundles have to be opened regularly, choose [resealable cable ties](en/closure-materials/cable-ties/resealable-cable-ties). These deliberately have a lower tensile strength – the release mechanism costs strength – but save you the cutting and the waste. For temporary bundling with no tensile load at all, [velcro fasteners](en/closure-materials/velcro-fastener) are often more practical still.

### Outdoors and permanent

Black, and preferably one size up from what you would choose indoors. The combination of UV, moisture and temperature cycling demands margin. For markings and temporary cordons outdoors, combine them with [barrier tape](en/barrier-tape).

### Heavy bundles, construction and industry

From 7.6 mm upwards you are in heavy duty territory. For pipework, fencing or scaffold sheeting, 9 to 13 mm and 79 to 114 kg are the usual choice. If the fastening also has to attach to a surface, look at [cable ties with a mounting eye](en/closure-materials/cable-ties/tyraps-with-attachment-eye) or [cable ties with an expansion anchor](en/closure-materials/cable-ties/cable-ties-with-expansion-anchor).

### Extreme: heat, chemicals and salt air

This is where plastic stops. Stainless steel banding reaches up to 230 kg, is indifferent to UV and does not lose strength at high temperatures. For bundles that change diameter often there is the [stainless steel ladder variant](en/closure-materials/cable-ties/stainless-steel-cable-tie-ladder-variant), which is easier to adjust than a smooth band.

### Special requirements: detection, identification and security

In the food industry, [detectable cable ties](en/closure-materials/cable-ties/detectable-tyraps) are mandatory: if a fragment ends up in the product, the metal detector finds it. If you need to identify cables, there are [cable ties with a marker label](en/closure-materials/cable-ties/cable-ties-with-marker-label) and [printed cable ties](en/closure-materials/cable-ties/printed-cable-ties). For attaching price and product tags so they cannot be removed, use [secure attachments](en/closure-materials/cable-ties/secure-attachments). For extra grip in the head there are [metal tooth cable ties](en/closure-materials/cable-ties/metal-tooth-cable-ties), and anyone looking to make their range more sustainable should look at the [eco-friendly cable ties](en/closure-materials/eco-friendly-cable-ties).

## Four mistakes that halve strength in practice

### 1. Reusing a tie that is not designed to be reopened

The head is damaged when you prise it open, even if you cannot see it. At the next load it slips through. If a bundle has to be opened regularly, choose a resealable version or velcro from the outset.

### 2. Running the strap over a sharp edge

As described above: a notch half a millimetre deep costs you more strength than dropping a size. Put something in between.

### 3. Cutting the tail off at an angle

An angled cut leaves a point that slices during maintenance, and weakens the head because material disappears from the locking mechanism. Cut flush against the head.

### 4. Calculating with the number on the box

The most persistent mistake of all. The stated tensile strength is the point at which the strap breaks, not the load you hang from it. Divide by three, or by four where vibration or weather are involved.

## In short

- The value on the packaging is the **minimum loop tensile strength** at room temperature – a breaking value, not a working load.
- Work with **no more than a third** of that value, and a quarter where vibration or outdoor exposure is involved.
- **Width determines strength; length only determines the circumference** of the bundle.
- Outdoors, always a **UV-resistant version**: the added UV stabiliser captures the radiation before it attacks the polyamide – in practice that means the black variant.
- For frost, heat, chemicals or salt air, choose a **specialist version** or stainless steel.
- Most failures come from a **sharp edge or over-tightening**, not from a tie that was too light.

## Ordering and advice

Our full range of [cable ties](en/closure-materials/cable-ties) is available in all common widths, lengths, colours and versions, and is held in stock alongside the rest of our [closure materials](en/closure-materials) – including [loop wires](en/closure-materials/loop-wires), heat shrink tubing and spiral wrapping band. Ordered on working days before 3:30 PM? Then your order will be shipped the same day. Enjoy free delivery on orders over €75 excl. VAT.

Do you have questions about which size of [cable ties](en/closure-materials/cable-ties) is best suited to your situation? Please don't hesitate to contact us — by phone on [+31 184 – 614256](tel:+31%20184%20-%20614256), via [info@kortpack.nl](mailto:info@kortpack.nl) or via [WhatsApp](https://wa.me/31184614256).

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Published: 2024-05-15 16:39:00
Source: https://www.kortpack.nl