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Your extrusion welding rod matters

Industry News | May 3, 2022 | By:

Solmax discusses why choosing your extrusion welding rod matters, and the best ways to perform an extrusion weld on a geomembrane.

A circular geomembrane extrusion weld
Circular geomembrane extrusion weld. Photograph courtesy of Solmax

Extrusion welding is a highly effective seaming method that’s primarily used for detailed patching work on polymeric geomembranes such as high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE). It also works well for seams around pipes, especially those in areas that are difficult to access with a wedge welder.  

But what are the key factors you need to consider to ensure a best-in-class seaming outcome? Proper preparation of the geomembrane sheets, temperature and welding speed are all important components for a successful result—but by far the most crucial is the compatibility of the welding rods you use.  

Extrusion welding involves the melting of a strip of polymer over the edges of overlapped geomembrane sheets to form continuous and impermeable bonding. Before the weld, the sheet surfaces must be prepared immaculately to clean the surfaces before applying the extrudate weld. A 0.16- or 0.20-inch (4- or 5-mm) diameter welding rod is commonly used to create an extrusion weld. The two geomembrane sheets to be joined should be positioned to create an overlap of at least 3.9 inches (100 mm), although some specifications allow an overlapping of 3.0 inches (75 mm).  

Extrusion welding involves the melting of a strip of polymer over the edges of overlapped geomembrane sheets to form continuous and impermeable bonding.

Extrusion welding is a highly specialized task, requiring professional operator skills and care for both the preparation and the technique itself. Engage a highly competent and qualified operator to carry out any kind of welding activity connected to a geomembrane installation. 

The compatibility of your extrusion welding rod 

In extrusion welding, the welding rod must be compatible with the geomembrane sheets to be welded. The rod should be made of the same polymer and, where possible, manufactured from the same materials as the geomembrane sheets.  

Extrusion welding of a geomembrane seam
Executing extrusion weld on a geomembrane seam. Photograph courtesy of Solmax

Using welding rods made from different materials can lead to incompatibility issues and seaming failures. Both the geomembrane sheets and welding rods need to have comparable melt-flow index and density. In addition, the rods should have comparable durability performance (i.e., stress-crack resistance, thermal-oxidative stability and UV stability) as the parent geomembrane sheets.      

For these reasons, to ensure optimal welding results, source your welding rods from the same manufacturer that supplied your geomembrane

This article first appeared on the Solmax blog.

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