Selecting the correct heat sealing band is essential for achieving stable, efficient and repeatable impulse sealing.
The sealing band defines how heat is stored, transferred and released into the material and therefore directly influences seal quality, cycle time and production rate.
Correct band selection ensures:
- Reliable seal strength
- Short and controllable heating cycles
- Efficient cooling
- Stable dimensional results
However, even with careful theoretical selection, the optimal sealing band can only be confirmed through practical sealing tests.
Band width, profile and function
The sealing band must have the correct width and profile to produce the desired seal geometry or cut-and-seal function.
The band must also have sufficient thermal mass to deliver the required heat into the material during the sealing cycle. In impulse sealing, the objective is always to terminate heating as quickly as possible once the sealing temperature is reached.
The seal is not fully formed until the sealed area has cooled below its softening temperature.
If the sealing band is too thick, or excessive energy is introduced, cooling time increases — extending the total cycle time and limiting production speed.
Material-dependent selection
Optimal sealing band selection depends on several interacting factors, including:
- Material composition and melting behaviour
- Material thickness and number of layers
- Heat absorption of the sealing jaw
- Type of cover strip used over the sealing band
As a general guideline:
- Thin films typically require thinner sealing bands for fast response and short cycles
- Thicker or multi-layer materials require bands with higher thermal mass to ensure sufficient heat penetration
Most films in the range of 1–6 mil (≈25–150 μm) can be sealed efficiently using sealing bands with thicknesses between 0.1 mm and 0.25 mm.
Sealing thicker and multi-layer materials
For thicker seals or multi-layer structures (up to 15 mil / ≈375 μm or more), thicker sealing bands may be required.
In some cases, applying heat from both sides of the seal should be considered.
When sealing unequal thicknesses, such as gusseted pouches:
- Two layers of 6 mil material result in a total thickness of 12 mil
- Four layers result in 24 mil, which represents a significant increase in thermal demand
Seals through uneven thicknesses can still be achieved with one-sided heating, provided that:
- The sealing temperature window of the material is respected
Sufficient sealing time is allowed for heat to penetrate through the thicker section
Heating from one side vs. both sides
Applying heat simultaneously from both sides can significantly reduce sealing time and improve heat penetration for thick or complex seals.
However:
- Dual-sided heating increases total heat input
- Cooling time may increase
Cooling time can be reduced by:
- Water-cooled sealing jaws
- Active air cooling of the seal area or jaw
Sealing tests – the decisive step
Despite guidelines and experience, material behaviour, layer structure and machine conditions vary significantly.
For this reason, the most reliable way to select the correct sealing band is to perform practical sealing tests.
Sealing tests make it possible to:
- Compare different band profiles, widths and thicknesses
- Identify the widest and most stable sealing window
- Verify seal strength, appearance and cooling behaviour
Detect shrinkage, deformation or sensitivity before production start
Testing ensures that the selected sealing band performs reliably under real operating conditions, not just in theory.
Vinther & Strand perspective
Selecting the correct sealing band is a balance between material behaviour, thermal requirements and cycle-time optimisation.
At Vinther & Strand, we support customers with:
- Selection of sealing band profile, width and thickness
- Supply of impulse sealing components
- Practical sealing tests to determine the most suitable band for each application
This approach ensures stable seal quality, reduced scrap and a reliable, production-ready sealing process from the outset.