Sealing pouches
Frequently asked questions about pouch welding
Both rigid and flexible plastic pouches are increasingly used in a growing number of fields. Welding is the most widely used method for assembling them, or simply for securing their closures, as it allows us to meet specific needs.
The sealing of bags or pouches requires the use of adapted machines to close or assemble them in specific environments. In the medical sector, blood bags must be sealed in an aseptic environment. In the packaging sector, pouches must be sealed to obtain an airtight container.
What welding technologies are used for the pouches?
The main technologies used for high-speed, high-volume pouch welding are ultrasonic and high-frequency welding.
High-frequency (HF) welding enables plastic parts to be joined using an electromagnetic field. This technology relies on the application of high-frequency electrical energy to produce highly resistant welds. Products requiring HF welding include blood bags, protective covers, inflatables, streamers, etc.
Ultrasonic pocket welding involves joining plastic components. As the name suggests, this technology relies on ultrasonic vibrations emitted by a sonotrode. This translates into an electric current with a frequency of 20 to 70 kHz, producing the molecular agitation required to join the parts. The resulting weld is both robust and durable.
What types of pouches are welded together?
Many industries use pouches that are assembled by welding. In office supplies, packaging and advertising packaging, the pouch sealing method is used to produce :
- Document protectors (commercial, medical),
- Door views,
- Plastic sleeves,
- Card protectors,
- Cases and pouches in various sizes,
- Adhesive or magnetic pockets,
- Stiff coquettes,
- Rigid boxes and cases,
- Single-seam pouches.
In the medical sector, pouches are either single or double-seam welded. This assembly technique means that welding is carried out on three sides to produce the pockets or pouches.
The medical bags most frequently assembled by double welding are :
- Infusion bags,
- Ostomy pouches,
- Blood bags.
In the press sector, the sealing of packaging blisters enables newspapers, magazines and journals to be folded and sent to their recipients.
What materials are welded together to make pouches?
Generally speaking, pouches are made from thermoplastics, which are the only materials capable of being welded together. Comprising 80% of the world’s plastics, they are assembled in this way:
- PVC (polyvinyl chloride),
- PET (polyethylene terephthalate),
- PP (Polypropylene),
- PS (Polystyrene).
The dichotomy between flexible and rigid plastics lies mainly in their chemical formulation. Materials such as PET, PS, LDPE and PVC enable us to design flexible plastics. This characteristic means they can be used to manufacture packaging, tarpaulins, pouches, etc.
PP, HDPE and ABS (acrylonitrile-butadiene-styrene) are among the rigid plastics used to manufacture weldable parts for a wide range of industries.
