How to choose the right plastic seal strap?

buy plastic seal strap

July 12, 2021

There are various plastic seal strap on the market. But how to choose the best plastic zip tie for your project? First of all, you need to figure out the purpose of your plastic seal. In this way, you can narrow down the range and select a plastic seal according to your actual application. This article will help you learn more about the plastic seal from the material, length, tension, structure, and label size.


The material of the plastic seal strap

At present, most manufacturers use PP+PE and PA66 these three materials to produce plastic seals.  


  The polypropylene material itself has features such as heat-resisting, acid resistance, water resistance, and anti-aging, which is very suitable for plastic seals. But the reason is its low cost. Besides, PP material is not soft, which is excellent for molding injection. However, if you only us the PP material, the plastic seal will be hard and has low tensile strength. To make the seal softer and improve the break strength, manufacturers will also add PE materials. Thus, it’s hard to break the seal when bending or folding. The working temperature of this kind of plastic seal is usually between -10 and 50 degrees. It will become brittle and easily broken if the operating temperature is too low. Therefore, in those low-temperature areas, you should consider adding some antifreeze material during the production process. Despite that, the plastic seal made of PP + PE materials is more suitable for laser engraving printing, which almost fits all applications.  


  PA66 was initially used to make plastic cable ties. PA66 is also known as nylon material. The material itself has the same features as PP material, such as heat-resistance, acid-resistance, water-resistance, and anti-aging. It’s also well shaped in the injection molding process. What’s more, the cable tie made of PA66 material is soft and incredibly flexible. There will be no white spots, no matter how it bends. Therefore, as soon as this kind of cable tie came out, it was favored by customers. However, compared with PP and PE materials, the cost is so much higher. Usually, the nylon cable ties have no tag or just a small flag. Therefore, it cannot meet all uses in our daily life. The working temperature of the nylon cable tie is between -15 degrees and 50 degrees. If you don’t care about the flag size or the printable area, the nylon cable tie is indeed the right choice.

Structure of plastic seal Strap

  According to the seal structure, there are non-insert seal, plastic insert seal, and metal-insert plastic seal. An insert is pretty much like a tiny chip with teeth to block the strap from pulling back.  

Non-insert plastic seal

  Many seals are one-piece construction without the plastic insert or metal insert in the locking chamber. Most of these plastic seals have a zigzag-shaped strap. The strap shall be threaded through the closure and into the locking chamber. The seal shall then be pulled up to the stopper. The cost of this kind of seal is lower as its production process is also less complicated. As long as you create the right mold, you will get a perfect one-piece construction plastic seal. And its pulling strength is also excellent.  

Plastic tie lock with metal clip

  To effectively prevent the plastic seal from pulling back, sometimes you will need to add a plastic or metal insert into the locking chamber when producing the plastic seal. The metal insert is more common in our daily life. Currently, there is a round or square shape metal insert. You may need a round-shaped metal insert for a cylindrical strap, while the square shape metal inserts for a flat belt. The strap of plastic seals with metal insert is very smooth, which takes less strength to pull the strap tight in the real application. Generally speaking, a seal with a metal insert is more secure than the seal without a metal insert.

Length of plastic seal Strap

  When selecting plastic seals, you also need to consider the operational length of the plastic seal. We divide plastic seals into adjustable length plastic seals, fixed-length plastic seals, and padlock seals.  


  An adjustable plastic seal does not mean that the total length of the seal is adjustable. It means you can adjust the closure diameter of the seal according to actual needs. For example, when you use a plastic seal to lock a box, you probably need a tiny closure diameter. What you need to do is pull the strap as tight as possible. However, no matter what kind of plastic seal, once locked, it cannot be removed. The seals are strong enough to resist removal except by using a wire cutter of scissors. The length of the adjustable seal is generally between 150 mm and 600 mm.  

Fixed length

  The total length of the fixed plastic seal is usually between 175 mm and 250 mm. Unlike the adjustable plastic seal, the closure diameter of this kind of seal is un-adjustable. This kind of seal has a bullet-shaped head on the end of the strap. Once inserted the bullet-shaped head into the locking chamber, the seal will be locked permanently. This fixed length strap seal has a wilder strap, perfect for sealing the truck trailer doors. However, compared with adjustable plastic strap seals, its less convenient.  

Padlock Seal

In addition to the above two plastic seals, there is a short and tiny seal with a small tag – padlock seal. This kind of plastic seal has a hook-like lock head. Once insert the lock head into the lock chamber, you will be unable to pull it out. This kind of disposable padlock seal is tiny, and there is minimal printable area and closure diameter for this seal. Despite those features, it’s very convenient to use it in daily applications.

Flag size


Big flag plastic seal

  So far, the maximum printable area flag we have 8×11 cm. We mainly use those big flag seals for locking mailbags and packages. Generally, some shipping companies want to print the serial number, barcode, text on one flag. If the tag is too small, there will be no enough printable area for a custom imprint. Simultaneously, the cost of a gigantic flag is also higher as it uses more material. What’s more, a large flag also means that printing is more complicated.  

Small flag plastic seal

  The small flag seals are trendy all around the world. In our daily life, small flag seals are more common. Most of the customers only request to print their logo or number on the flag. A small flag is fair enough to make such an imprint. The custom imprint for a small flag seal is faster, and the cost is lower.

Tensile strength.

  Several factors affect the tensile force of plastic seals, including the material, the width of the strap, and the metal insert. Generally speaking, the material used for manufacturing plastic seal will affect its tensile strength. For example, nylon or PE material has a better break strength. Also, the break strength for a thicker strap seal is higher. If you add a metal insert, the break strength will be even higher. We can divide the plastic seals into low tensile plastic seals, medium tensile plastic seals, and strong tensile plastic seals according to the tensile strength. Most of the small plastic padlock seal and the tear-off plastic seal is Low-tensile strength seals. One can break those seal with the bare hand. Their tensile force is less than 20KG. The medium tensile plastic seals mainly have a tensile strength above 20KG and below 40KG. We classify plastic seals with a tensile force above 40KG as high tensile plastic seals. Must we choose strong tensile strength plastic seals? Of course not. It depends on the real application. For example, when we choose a plastic seal for those takeaways, we prefer the seal to be removed easily with bare hands. In this case, you’d better choose low tensile strength seals such as tear-off seals. In summary, there are many types of plastic seals with different lengths, shapes, materials, and break strength. When choosing the right plastic seals, you’d better tell the supplier how you will use the seals. So the supplier can introduce the correct seal that fits your needs.

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