Basics of impulse sealing: how it works, advantages and applications

What is impulse sealing?

Impulse sealing is a process in which plastic films, packaging or parts are joined together by means of temporary heat.

The special feature is the low mass of the heating element. It reaches the desired welding temperature in just a few milliseconds and then cools down again quickly, enabling controlled curing of the joint before the next production step.

Long heat-up phases and unwanted waste heat in the machine and product can be reduced and even partially avoided with impulse sealing.

Thanks to ROPEX control, the temperature of the heating element and its effective time are identical in every cycle of the system, ensuring very high repeatability of the welding results.

The heating element and/or the counter layer are also made of a flexible material that can be produced in a wide variety of contours. This opens up countless application possibilities, particularly in packaging technology as well as the medical and food industries.

How it works

Preparation: Two plastic parts are fixed in the desired position.

1. Heating. An electrical impulse heats the heating element for a few milliseconds, melting the plastic surfaces in the welding zone.

2. Cooling. After the current is switched off, the heating element cools down again immediately.

3. Result. A stable and tight weld seam is created that meets the requirements of the respective area of application.

Thanks to modern control systems, this process is precise and repeatable, even in complex applications.

Suitable materials for impulse sealing

The process is particularly suitable for thermoplastics as these melt when exposed to heat and form a permanent bond after cooling. Frequently used materials are:

Polyethylene (PE): often used in packaging and films as it is both flexible and robust.
Polypropylene (PP): ideal for medical and chemical applications thanks to its high temperature resistance.
Polyvinyl chloride (PVC): often used in technical applications as it is highly resistant.
Polyester (PET): for film packaging and other applications that require transparency and stability.
Special films: laminated or coated materials, such as aluminum laminated films, metalized films, high barrier films, paper-based films used in demanding areas such as the food or pharmaceutical industries.
Biofilm: an environmentally friendly alternative that is biodegradable and increasingly used for sustainable packaging.
Cellulose-based films: made from natural polymer. The main component is plant cell walls; these films are ideal for applications where sustainability is a priority.
Mono-materials: consist of one material, as opposed to multi-layered or a mix of several different materials.
Post-Consumer Recycled (PCR): recycled materials that are recovered from end-user waste, reprocessed and reused to manufacture new products or packaging in order to conserve resources and reduce environmental impact.
PIR (Post-Industrial Recycled): refers to recycled material from industrial production waste generated during manufacturing before the product reaches the consumer. It is often of higher quality than Post-Consumer Recycled (PCR) as it contains fewer impurities and can flow directly into new production processes.

The choice of material depends on the requirements of the application, such as chemical resistance, flexibility or transparency.

Advantages of impulse sealing

The most important advantages of impulse sealing are:

Efficiency: Impulse sealing is characterized by particularly fast process times, as the heating and cooling phases are very short. This means that a large number of solid weld seams can be produced in a short time (due to the direct cooling phase of the seam area after the welding process), which significantly increases productivity.
Precision: Thanks to the exact control of temperature and pressure, a uniform and high-quality weld seam is guaranteed. This is particularly important in areas where high demands are placed on the tightness and strength of the joint, for example, in the medical and food industries. The heat sensitivity of the material also plays a decisive role in this regard: mono-material films, especially those made of plastics such as polyethylene (PE) or polypropylene (PP), often have a narrow temperature range in which they can be welded without being damaged (e.g. by burning or shrinking).
Material protection: The targeted heat effect is limited to the weld seam and prevents the packaged goods from being affected. This is particularly advantageous for sensitive or thin materials, as damage or deformation can be avoided.
Versatility: The contour of the tools can be individually adapted. When it comes to small heating elements with a diameter of 15 mm for heating bonding points to welding thick materials or producing separating, peel and flat seams, impulse sealing offers flexible solutions.

Areas of application for impulse sealing

Impulse sealing is used in a wide variety of industries and end products. The most important areas of application are:

Packaging industry: sealing bags, pallet wrappers and processing flexible packaging.
Medical products: sterile sealing of medical packaging, such as infusion or colostomy bags, blood filters, catheters.
Food industry: sealing frozen foods such as chips and vegetables or sealing spouts for refill packs.
Technical applications: production of construction films, technical membranes or FemCare products such as sanitary towels.
Pharmaceutical industry: precise processing of sensitive materials under clean room conditions. End products include bioreactors, 3-D bags or infusion bags.

Future prospects for impulse sealing

The further development of the process opens up new possibilities:

Sustainability: The requirements for resource-saving and environmentally friendly manufacturing processes are constantly increasing. Impulse sealing supports this development through the targeted use of energy and the ability to efficiently process sustainable materials such as bioplastics and cellulose-based films as well as recycled materials such as PCR and PIR films.
Special applications: New, innovative technologies enable the processing of increasingly complex material combinations. Impulse sealing is increasingly being used for demanding applications in which different layers and materials need to be joined together without losing their individual properties. This opens up new possibilities in the medical and automotive industries, where precise and reliable joints are crucial.

Conclusion

Impulse sealing is a versatile welding technology that is used for a wide variety of end products. The precisely reproducible temperature control and flexible design of the welding tools make it one of the most attractive technologies for welding thermoplastics. If you would like to find out more about the technological possibilities, you can find detailed information on the corresponding product and technology pages.