Assembling truck tarps often requires joining multiple pieces of PVC-coated fabric. Whether it’s to create a large tarp, make borders, or add tie-down loops or fastening systems to retractable systems or curtain tarps, it’s rare for a single piece of fabric to suffice. But how can you ensure that these joints will withstand the rigorous demands of trucking?
The tarp manufacturing industry, whether for truck tarps or tarps for industrial buildings, mainly uses two technologies to join two pieces of fabric: hot air welding and high-frequency thermosealing. Two very different technologies that it’s good to know about to better understand their advantages and limitations.
Hot air welding is probably the most widespread technique. Inexpensive, flexible, and simple to operate, this technique requires relatively lightweight and less expensive equipment. The principle is quite simple: using a device that looks much like a heat gun, heated air at around 700 degrees Fahrenheit (370 degrees Celsius) is blown between the two pieces of fabric to be welded, and pressure is applied. The heat melts a thin layer of vinyl, and pressure bonds the two pieces together.
On the other hand, high-frequency thermosealing is a more sophisticated technology, requiring the use of more expensive equipment and a more complex operation. High-frequency thermosealing uses, as its name indicates, a wave frequency that has been specifically allocated by the government, the ISM frequency, for industrial, scientific, and medical purposes. This frequency is set at 27.14 megahertz.
The thermosealing equipment is equipped with a press of varying length and width, depending on the applications. This press sends waves into the two fabrics being joined, which, for 3 seconds, change polarity 27.14 million times per second. These polarity changes create friction of the PVC molecules and completely fuse the PVC of the two fabrics. Thus, two vinyl pieces become one single piece.
You will understand that a joint created by high-frequency thermosealing will be more resistant than one made by hot air welding. According to Pierre Bourdeau, President of P.T.T. High-Frequency Thermosealing Systems, this technology creates joints twice as resistant.
“Tests have been conducted on the materials using a ‘pull test’ device, which pulls the fabric until it shears. These stretch tests, for the most part, were done at CRIQ. In general, it can be stated that thermosealing is twice as resistant to shear as hot air welding. In fact, when attempting to break a tarp that has been made by high-frequency thermosealing, it’s not the joint itself that gives way, it’s the fabric next to it. The joint is actually stronger than the rest of the fabric.”
But thermosealing has its limits and requirements. Due to the waves used by this advanced technology, the materials must be extremely clean. A dirty tarp, which has been exposed to sunlight for too long, or which has been in contact with contaminants or chemicals such as chlorine, cannot be assembled by this process. Thus, there’s no question of making repairs to a used tarp with thermosealing.
Hot air welding is also more practical for small additions like tie-down straps or small pieces of fabric for retractable system arches.
At Alyak 2000, we have opted for these two different fabric assembly techniques to reap all the specific benefits of each technique. Thus, large assemblies of new tarps are made using a high-frequency thermosealing Cosmos-Kabar machine, one of the most recognized manufacturers in the world. For repairs and joints of smaller pieces of fabric, Alyak 2000 relies on the high performance of Leister hot air welding devices. The best of both worlds, isn’t it?
