Pre-stretch ratio is one of the most important factors affecting stretch film performance. For factories using stretch film to secure pallets and loads, selecting the appropriate pre-stretch ratio can influence film consumption, load stability, wrapping efficiency, and overall packing costs.
A higher pre-stretch ratio does not always mean better performance. The ideal ratio depends on the film structure, film thickness, wrapping machine, load characteristics, and required holding force.
Pre-stretch ratio refers to how much a stretch film is elongated before it is applied to a pallet or product.
For example, if 1 meter of stretch film is stretched to 2 meters before wrapping, the film has been stretched by 100%.
Common pre-stretch levels may include:
The actual performance depends on both the stretch ratio and the film's ability to maintain its mechanical properties after stretching.
One of the main advantages of pre-stretching is reduced film consumption.
When the film is stretched before application, a smaller amount of film can cover a larger area. This can help factories reduce the amount of film required for each pallet.
For example, a film with a 200% pre-stretch ratio can theoretically extend to approximately three times its original length, although actual usable stretch depends on the film and wrapping conditions.
Lower film consumption can result in:
However, excessive stretching can reduce film thickness and may affect its ability to resist punctures and tears.
Load stability is another important performance factor.
Stretch film must generate sufficient holding force to keep products securely together during transportation and storage. Pre-stretching can help create tension in the film around the load.
An appropriate pre-stretch ratio can provide:
If the film is overstretched or the wrong film grade is selected, the wrapping force may not be sufficient for certain heavy or unstable loads.
It is easy to assume that a higher stretch ratio automatically provides better efficiency. In practice, this is not always true.
When film is stretched too far, several problems may occur:
Therefore, factories should select a pre-stretch ratio according to the actual application instead of simply choosing the highest available ratio.
Film thickness and pre-stretch ratio should be evaluated together.
A thinner film with a high stretch ratio may provide excellent material efficiency, but it needs to maintain sufficient strength after stretching.
A thicker film with a lower stretch ratio may provide greater resistance to punctures and tears but consume more material.
The best combination depends on:
For this reason, comparing stretch film only by nominal thickness can be misleading.
Pre-stretching changes the physical characteristics of the film.
As the film is stretched, its molecular chains become more oriented. This can improve certain mechanical properties in the stretching direction while reducing the remaining elongation available during wrapping.
The result depends heavily on the film's raw materials and manufacturing process.
High-quality stretch film is designed to maintain a suitable balance between:
A well-designed film can therefore achieve high stretch efficiency without sacrificing essential load-protection properties.
The wrapping machine plays an important role in determining the appropriate pre-stretch ratio.
Pre-stretch machines use rollers with different speeds to stretch the film before it reaches the load. The selected ratio depends on the machine's roller configuration and control system.
Factories should consider:
If the film and machine settings are not properly matched, the film may break, stretch unevenly, or fail to provide sufficient load stability.
There is no universal pre-stretch ratio for every factory.
A practical selection process should consider the following factors:
Heavy pallets generally require reliable containment force and sufficient film strength.
Sharp corners and irregular shapes can create additional stress on the film.
Smooth products may require different wrapping tension compared with products with rough or uneven surfaces.
Long-distance transportation, repeated handling, vibration, and temperature changes may require stronger load containment.
Automatic and semi-automatic machines may operate with different pre-stretch settings.
Film thickness, material structure, and mechanical properties all affect the recommended stretch ratio.
Before switching to a higher pre-stretch film, factories should test the film under actual production conditions.
A useful test can compare:
This provides a more accurate picture of overall film efficiency than simply comparing the stated stretch ratio.
When properly selected, pre-stretch film can help factories reduce total wrapping costs.
Potential savings can come from:
Lower film consumption + fewer roll changes + reduced waste + improved wrapping efficiency
However, factories should calculate the cost per wrapped pallet rather than focusing only on the price per kilogram of film.
A higher-performance film may have a higher price per kilogram but still reduce the total cost of wrapping because less film is needed for each load.
Pre-stretch ratio has a direct impact on stretch film consumption, load stability, mechanical performance, and packing efficiency. A higher ratio can increase material efficiency, but excessive stretching may negatively affect puncture resistance, tear resistance, and wrapping reliability.
For factories, the best approach is to match the pre-stretch ratio with the film specification, wrapping machine, and load requirements. Testing different options under real production conditions can help identify the most efficient combination of film performance and cost.
Looking for stretch film with a suitable pre-stretch ratio for your factory? Contact NAIGU to discuss your required film thickness, stretch ratio, width, and application.
