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Different Methods for Melding Materials Together

Updated on June 11, 2013

My family and I recently spent a day at the local pool, at which some people were using flotation devices (like those inflatable water wings) and inflatable rafts. I was thinking about how it's not all that rare to see someone flop onto a raft and have it pop immediately, and wondering how they're made. I had heard of heat sealing before, which involves simply applying heat to two pieces of material until they melt together and form a bond, but when I went home I felt like doing some casual research and found out there are a few different ways these sorts of products can be made. And it turns out, there's a variety of different industries that use the processes for their goods.


Different Ways to Meld Materials

I learned that there are basically four different ways that materials like vinyl, PVC, and polyurethane can be bonded together. There's radio frequency welding, hot air sealing, hot wedge sealing, and solvent binding. They're all somewhat similar, in that the end result is a strong, durable seam that has bonded materials together, but the way each of them works is distinct.

Radio frequency welding works by applying electromagnetic energy and pressure to bond materials together. The electromagnetic energy loosens then rearranges the molecules of the materials, and then they are fused together. RF welding can be used on a wide range of materials, and the melded seam is at least as strong as, if not stronger than, the original material. This type is typically used to mass produce products where uniformity is essential.

Hot air sealing is a bit different, and a bit simpler. This method uses heat and pressure to bond materials together, and is a much faster process than radio frequency welding. It works with a wider range of materials than other methods of sealing, and is especially a good option for larger items or items that need curved seams. It also works well for products that are inflatable. One shortcoming of hot air sealing is that it can only bond two surfaces at one time.

A third option is hot wedge sealing. Hot wedge sealing can bond together two more layers of material, and involves using a rotary press to apply pressure and heat at the same time to fuse the materials together. It creates a permanent, tear-proof seam. In addition to producing seams for products that lay flat, hot wedge sealing can create three-dimensional objects as well. It's ideal for connecting large sections of coated fabrics—like the background fabric at tennis courts or pool covers.

Finally, there's solvent bonding, which is exactly what it sounds like. In this process, a solvent is applied to the materials, which softens and dissolves the material. As the solvent evaporates, the bond is formed. It's a process that's used mainly for successfully fitting fill and vent tubes, like inflatable products that need a valve/tube for inflating them—imagine the valve on an inflatable innertube that you'd bring to the pool.

Once I learned that there were four different ways to meld materials together to form larger products, I kind of wondered what sort of industries used them, so did a little bit of research on that and was pretty surprised to see the reach that these processes have.

What Industries Employ These Processes?

Now, obviously, industries that create supplies for the beach (inflatable rafts) use these methods to make their products. But many other industries do, too. For example, the medical and pharmaceutical industries use them to make IV bags and blister packaging. IV bags benefit from the strong, durable seam because the contents of IV bags need to remain sterile in order to be safe for medical use. These processes may also be used to make airlift bags and other airlift supplies.

The automotive industry uses these processes to meld detailing onto seat covers. Since vinyl welding is one of the common applications for these processes, it's not surprising that it would show up in cats. At car washes, curtains can be constructed with heat-sealed materials since they are easy to clean and waterproof.

The military also uses these melding processes. For military use, the impervious, water- and air-tight seams are especially valuable for things like weatherproof vehicle and weapons-system covers and when creating water and fuel tanks. It's also used for submersible weapons transport bags, as well as pre-conditioned air hoses for aircraft.

These processes can also be used for safety—when creating hazmat suits and hazmat shelters, it's important not only for the seams to be durable but also leak-proof, both of which these processes ensure.

If you've never heard of radio frequency welding or the processes similar to it, it's an interesting concept that's probably been applied to more things than you'd expect. Take a look around your everyday life—chances are, you use something that's been a product of these processes at least once a day.


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