Ever had a zip tie you just installed break? Or maybe it broke after some time? It turns out that there can be several reasons for this. It is not always the result of poor product quality. Sometimes it’s due to our incorrect installation method or the wrong choice of tie for the specific application. So let’s take a look at the most common causes of cable ties breaking:
The most obvious cause of cracking can of course be poor product quality. The most common material used in the production of cable ties is polyamide 6.6, also known as nylon 6.6. Despite being described by the same chemical formula, several different types of polyamide granulates are provided by different suppliers on the market. As a result, cable tie manufacturers get a whole range of different raw materials, sometimes with significantly varying parameters. Which is how a single manufacturer can use different raw materials from different suppliers, to produce one series of cable ties. This results in products that are identical at first glance, with the same catalog parameters, yet on closer examination have different mechanical properties. The differences usually occur in properties that are not commonly reported, such as elasticity or hardness. Other factors contributing to the issue are a possibly faulty production process, damage to the injection mold or injection molding machine, as well as the amount and type of additives added to the raw material.
To minimise the risk of premature breaking, it is best to use cable ties from reputable companies, that care for maintaining the quality of their products, for fear of losing their good reputation on the market. Companies that are not ashamed of their products mark them (not just their packaging) with their logo or other proprietary markings. We recommend using cable ties marked with the manufacturer’s logo, its name or a specific abbreviation. Note that the numerical marking on the cable tie indicates the number of the slot in the injection mold (in order to more easily locate potential mold damage).
2. Water saturation
A particularly important parameter, often playing a key role in the cracking and breaking of ties, especially during installation, is their water saturation. This is due to the fact that most plastics are hygroscopic, i.e. they absorb water from the environment. This can be compared to raw wood, which soaks up (absorbs water) when the environment is wet, and dries out (gives up water) when the environment is dry. Of course, different materials have different levels of absorption. Depending on the degree to which a material soaks up water, its mechanical performance changes. Here we focus on the most common material from which zip ties are made – polyamide 6.6. When dry, it is both hard and brittle, but has very good tensile strength. On the other hand, when too saturated (e.g., after lying in water for a long time) it begins to stretch like chewing gum. To achieve the optimal water saturation, ties are appropriately conditioned after the injection molding process. An appropriate amount of water is added to the sealed package and the ties are left to soak for 6 weeks, until the water is absorbed by the material. This mimics the standard humidity of the air (50%), the natural working conditions of the ties, and ensures optimal mechanical properties – the highest possible tensile strength (the drier the material, the higher the tensile strength), while maintaining adequate flexibility. Although the factory saturation of cable ties corresponds to natural conditions, there are applications when the working environment is much drier. This occurs most often in winter, but also in air-conditioned rooms, when lowering the temperature causes the water contained in the air to condense. Cable ties applied in such conditions begin to dry out, losing their elasticity. While a change in humidity has little effect on ties already installed, the impact on those yet to be fixed can be colossal. The sensitive connection between the ratchet, skipping along the serrated band, and the head of the tie is most affected. This small area most often breaks during installation.
Therefore, it is recommended to control the humidity in the storage and installation space, and to store ties in a tightly closed package. For the same reason, keeping cable ties in areas exposed to high temperatures (such as next to a radiator or in a very sunny place) is not recommended.
3. UV radiation
Ultraviolet radiation which is present in sunlight, among other things, has an adverse effect on the durability of materials, and most of the materials commonly used to make cable ties are not resistant to it, including polyamide 6.6 (nylon 6.6.). Ultraviolet radiation penetrates into the structure of the material, causing its degradation and breaking of intermolecular chains. As a result, the material becomes brittle and fragile (so-called aging effects). To avoid this (according to ASTM D6779), 2% of carbon black (soot) is added to the polyamide, preventing UV radiation from penetrating the material. This makes it more resistant to aging and helps maintain proper elasticity.
Note that not every black band (with carbon black added) is UV resistant. Manufacturers also use soot simply to dye the ties, but in this case the amount added is much less than the 2% required by the standard.
4. Tightening force
Cable ties, like any product, have their maximum tensile strength. This value is determined by manufacturers after testing their products and can usually be found in the technical specifications. The recommended maximum force used to tighten the cable tie is also provided based on the tests. If the user does not control the tensioning force and exceeds it, the cable tie (usually the latch area) can break during installation. Sometimes when the recommended force is exceeded, but not by enough to immediately cause a rupture, the tie can crack under any additional loads, for example in the event of dynamic vibration.
Therefore, it is recommended to use professional tools with adjustable tension settings for tightening cable ties, in order not to exceed the recommended values.
Visit our store, where you will find a wide range of cable ties and tightening guns for their safe installation.