- Plastic Sealing/Welding Technologies
The purpose of this article is to outline the most commonly used heat sealing technologies in the Industrial Fabrics market using Engineered Textiles with
Polymercoatings. Advancements in industrial materials/fabrics, such as greater heat resistance and strength, stronger weaves and coatings, and consistency roll to roll have opened the market up to new applications. These new applications have created a greater demand for sealing technologies that deliver more consistency and speed.
For example, we now have flexible hurricane shields, inflatable aircraft slides, fire resistant clothing, and countless new military products. Applications also exist in the
Automotive industry, Photographyproducts, Media storage,and retail promotion.
Common Product examples
Loose leafbinders, Checkbooks, Passport holders, and Shower curtains.
Radio Frequency Welding (RF)
Radio frequencywelding is a very mature technology that has been around since the 1940s. Two pieces of material are placed on a table press that applies pressure to both surface areas. Dies are used to direct the welding process. When the press comes together, high frequency waves (usually 27.12 MHz) are passed through the small area between the die and the table where the weld takes place. This high frequency (radio frequency) field causes the molecules in certain materials to move and get hot, and the combination of this heat under pressure causes the weld to take the shape of the die. RF welding is fast. This type of welding is used to connect polymer films used in a variety of industries where a strong consistent leak-proof seal is required. In the Industrial Fabrics Industry, RF is most often used to fuse/weld vinyl (PVC) and polyurethane(PU) coated fabrics. This is a very consistent method of welding.
Please note that Exposure conditions experienced by RF heater operators can cause elevated body temperature, eye irritation, RF burns, and some neurological problems. To reduce exposure conditions the use of
Electromagnetic shieldingshould be used as much as possible without hindering the manufacturing process.
The most common materials used in Radio Frequency Welding are Thermoplastics such as PVC and Polyurethane. It is also possible to weld other polymers such as Nylon, PET, EVA and some ABS Resins
* [http://www.lynvale.co.uk/process9.php An example of the Radio Frequency Welding Process and its uses]
Hot Air/wedge Welding
Hot air welding uses hot air or a wedge to heat the coating on the fabric where it is to be bonded together. A Nozzle or heated wedge is positioned between two rollers that pull the material through the machine. As the material is pulled through the machine, hot air is applied to the surfaces to be fused together. Pressure from the rollers and heat form the hot air cause the plastic to fuse as the plastic cools. Like Radio Frequency RF--thermal welding is fast.
Ultrasonic weldinglike radio frequency welding creates heat through friction, however,the heat is created between two layers of material rather than within the material itself. It uses a vibrating tool (die) to create the heat. Ultrasonic can be used on almost all plastic material. It is the fastest heat sealing technology available. It is a rather new technology for Industrial Fabric applications, however it can be more costly to weld large surface areas.
Friction welding/ Welding/ Plastic welding
J. Alex Neumann and Frank J. Bockoff, "Welding of Plastics", 1959, Reinhold publishing.
Safety in the use of Radiofrequency Dielectric Heaters and Sealers, ISBN 92-2-110333-1
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