In the industrial packaging sector, securing a pallet is not simply a matter of applying maximum tension with the strapping tool. In fact, applying excessive force is often a major cause of damaged goods, loose strapping, and accidents during transport.

To understand how to keep a load fully stabilized from the moment it leaves the warehouse until it reaches its destination, it is essential to understand a technical concept from materials science: the elastic limit.

1. What is the elastic limit of a material?

The elastic limit It is the maximum stress that a material (such as steel or polymers) can withstand without suffering a plastic or permanent deformation.

When we apply a force to a strip, its mechanical behavior goes through two clearly differentiated phases:

• Elastic zone (Reversible deformation): The material stretches under tension, but as soon as the force is removed, it returns to its exact original length. It works just like a spring.

• Plastic zone (Permanent deformation): If the force exceeds the elastic limit, the internal structure of the material is irreversibly altered. The strap remains stretched and does not return to its original state. If the tension continues to increase, the tensile strength is reached and the strap breaks.

       Tension (force) ^ | / | / <- Plastic Zone (Permanent Deformation) | +----+ | / <- Elastic Limit | / |/ <- Elastic Zone (Recovers shape) +----------------------------> Deformation (elongation)

2. How does the elastic limit affect the strapping during transport?

During transport, pallets are subjected to vibrations, sudden braking, bumps, and temperature variations. Furthermore, many goods (such as sacks, cardboard boxes, or wooden crates) settle and compress over time.

The behavior of the strapping within or outside its elastic limit determines the final result:

A. Shock absorption (Spring effect)

If the strapping has been applied within its elastic range, it will absorb the truck's inertia. The strapping will momentarily elongate during sudden braking and will contract again, maintaining constant tension on the pallet.

B. The risk of voltage loss

If the strapping machine exceeds its elastic limit during tensioning, the strapping will permanently sag. When the pallet experiences its first movement or settling, the strapping it will not contract, leaving it loose and making the load completely unstable.

3. Behavior according to the type of strapping: PET vs. Steel

The choice between one consumable or another depends directly on the mechanical properties required by the type of load:

• Polyester (PET) Strapping: It possesses high elasticity and tensile strength. It is the ideal choice for loads that undergo settlement or volume reduction during transit, as it maintains residual tension thanks to its wide elastic range.

• Steel Strapping: It features an extremely high yield strength but minimal elongation. It is designed for heavy, rigid loads with no compressive capacity (such as ingots, tubes, or metal components) where zero deformation is required.

4. Ensure secure packaging with Sorsa Packaging Systems

Determining the exact strapping tension and selecting the appropriate consumable requires a precise analysis of the packaging process. Sorsa Packaging Systems, We combine high-precision strapping machinery with consumables tested under the strictest materials engineering standards.

Frequently asked questions about the elastic limit in strapping

What happens if the elastic limit of a strap is exceeded?

If the elastic limit is exceeded, the strap enters the plastic deformation zone, losing its ability to return to its original length. As a result, the strapping will be loose and prone to movement of the load during transport, increasing the risk of instability and breakage.

What is the difference between elastic limit and tensile strength?

The elastic limit This is the maximum point to which the strap can stretch and return to its original shape without deforming. tensile strength It is the maximum total force that the strap can withstand before it finally breaks.

Why does PET strapping have better elastic memory than steel strapping?

Polyester (PET) strapping has a polymeric molecular structure This allows it to elongate and recover its initial tension (elastic memory) after impacts. Steel, although it can withstand heavier loads without stretching, will permanently deform or break if it exceeds its elastic limit.

How can you tell if the strapping machine is applying too much tension?

If, upon removal of the load, the strapping shows permanent curves, a noticeable loss of rigidity, or deep marks of permanent deformation without having suffered external impacts, the strapping head is exceeding the elastic limit of the consumable.

Do you want to check if your strapping maintains optimal tension during transit? Contact our specialists and we will analyze the operational needs of your logistics chain.

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