Using PVC-Coated Weldable Polyester Webbing
with Fabric Structures

Various grades of PVC-coated webbing, and the techniques of welding them into place rather than sewing, are now established materials and methods in the awning, tent, and tensile structures industries.

With weaves rated up to 16,500 pounds of tensile strength. PVC-coated webbing can be an important building component in all types of fabric structures. It is properly left to the design engineer where and how to employ the flexible strength offered by coated webbing, but several generalizations should be understood to best understand the products and their functionality.

1. Webbing is Webbing. Beneath the outer vinyl coating is simply a woven polyester webbing exactly similar to like-rated webbings without coatings. Because they are woven to be inside a coating, these weaves are termed "scrim". They are usually raw yarns, not dyed or treated with any special finish, because they are meant to be coated. In fact, it is best that they are clean and not contaminated with any foreign substances to obtain the highest quality adherence with the vinyl coating. Nevertheless, the weave structure of these scrim webbings is designed and calculated just as if the web were to be used uncoated. That is, the yarn counts, the edge finishes, the density, the flexibility, and the general performance factors such as stretch and tensile strength are all skillfully considered and managed as they would be in any industrial weaving application.

2. Advantages of Coating. Depending on how it is formulated vinyl (PVC) can provide a strong but flexible, waterproof coating over various types of scrim fabric. Clearly, coated tent fabric has proven to be a superior structural and weatherproof material compared to canvas. Similarly, coated webbing also has a waterproof outer surface that both repels moisture and is easier to clean. Coated webbing, thus, offers many performance advantages over traditional materials just due to its non-wicking composition. Importantly, the pvc coating on the webbing can also be welded to the pvc coatings on many types of industrial fabrics. Thus coated webbing is an ideal structural component used for shaping and strengthening tents and tensile structures.

3. Welding Considerations. Achieving a satisfactory fabric-to-webbing weld can be a complicated matter. Different welding methods and equipment offer a variety of material handling advantages. But the method used to actually perform the weld, and the range of possible materials to be welded, creates a sometimes challenging experimentation and testing process for production workers. In some cases, welding equipment can be left alone and used just as if it were set up to weld two exactly similar edges of tent fabric. In other cases, however, the density of the webbing can vary greatly from the lighter tent fabric. This can require using lighter power and/or longer dwell times on high frequency equipment. With hot air welders, heat is directed between (not through) the materials and thus it should be in the right place. But it is necessary to control the heat so that the lighter tent fabric is not damaged while attaining sufficient temperature to soften the coating on the heavier webbing. Heat can also cause vinyl coatings and the underlying polyester scrim fibers to stretch, shrink, or otherwise distort. Thus it is always desirable to consult with your equipment manufacturer and to run several test welds before beginning production runs.

4. Product Advantages and Concerns. Coated webbing offers a clean, shiny appearance and does not pick up dirt as easily as porous, non-coated products. It is thus more easily washed or cleaned. Because it is sometimes sewn to add reinforcement to foldbacks, curves, and other structural elements, it is helpful to note that the unavoidable needle holes caused by stitching can usually be resealed by lightly passing a heat gun over them after the sewing is done. It is important to remember that the surface of the vinyl coating, while flexible, can be worn or cracked by folding it too tightly over fastening hardware or repeatedly running it through ratchet devices.