How is the Weld Strength of TPO Tested?

By Thomas J Taylor PhD 01-28-2016
QUICK SHARE
Tag Icon

One of the selling points of heat-weldable single-ply membranes is that the final result is a single welded sheet of membrane covering the roof. There are no adhesive seams to pop loose and a properly welded area is often said to be twice as strong as the rest of the membrane since it's twice as thick. This all sounds good, but how does the manufacturer test weld strength? Here is a look at what we do at GAF.

The first step is to weld some TPO with the same equipment and settings that are used on a roof. In fact, we make many welds at varying speeds and temperatures to cover most conditions.

welder

We recommend roofers do a test weld at the start of each day, after lunch, and whenever conditions have changed. The strips are then cut and pulled to check quality. Here's a cross section of what a weld cut actually looks like:

At GAF, we do the exact same thing. However, instead of doing a manual pull, we use some sophisticated test equipment, which enables us to measure the actual strength. (We use a physical property tester made by Instron.) The sample gets mounted between two steel jaws and pulled as shown here:

The machine records the force needed to make the pull. If you look at the center picture, you can see that the cap layer has just broken. After that, the cap peels away from the core, as can be seen in the right-hand picture. If the weld itself opens up, then it's a bad weld. The picture on the right shows what we call a film tearing bond. We've torn the cap or core film right off the membrane, exposing the reinforcement fabric, also known as scrim.

Our tester reports the force as a graph that looks like this:

This shows that it took a peak force of around 48 pound-force to break the cap or core. Then, to peel the cap from the core, it took around 20 pound-force. These are strong numbers that demonstrate the strength our sheets.

At GAF, we quality test our membrane this way. This ensures that the product welds and is the same strength day after day, mile after membrane mile!

Learn more about TPO and which brands perform best at www.tporesults.com and watch our how-to video on hand welding.

Don't miss another GAF RoofViews post!
LATEST UPDATES
Roof trusses provide the structural support for a home's roof, supporting the roof deck material, insulation, and any loads that are placed on the roof. As a result, they have to be strong enough to withstand wind, rain, snow, and any other types of weather that your region might be prone to.
This May, GAF teamed up with This Old House to support their "Protecting the Protectors Contest". The contest was established to give back to first responders who go above and beyond protecting their communities. Watch this video to see how first responders JoAnna, an oncology nurse, and her fiance Andrew, a firefighter, reacted to their brand new GAF Timberline HDZ roof.
Although the GAF Master Select contractor Aqua Seal Manufacturing and Roofing Inc. has a robust team of 100 employees, the workload in the Columbia, South Carolina, metro area always has them looking for more help. As one of the top commercial roofing contractors in their market, they do everything from new construction to reroofing—and their leak detection skills have kept them in high demand for years.
Thinking about switching to a pre-cut shingle starter strip from a cut up 3-tab asphalt shingle? Don't delay. Starter Strips save you time cutting 3-tab shingles, have properly positioned adhesive to help reduce the risk of shingle blow-offs, and allow you to create clean, finished roof edges. Want more details? Here are answers to all your questions about making the switch to pre-cut Starter Strips.
Building a brand-new 250,000-square-foot manufacturing plant and bringing it online takes collaboration, creativity, and teamwork. The newest GAF plant in New Columbia, Pennsylvania, is a testament to how hard work, support from the community, and flexibility all contributed to bringing this new facility to life.
After Danny McLaughlin became the president and CEO of Scro's Roofing Company in 2011, he looked for new ways to scale the business—and he was successful in doing so. "It was on my heart for a long time to be successful but not to stop at success," says McLaughlin. "I wanted to teach others how we got here."
This blog contains information created by a variety of sources, including internal and third party writers. The opinions and views expressed do not necessarily represent those of GAF. The content is for informational purposes only. It is not intended to constitute financial, accounting, tax or legal advice. GAF does not guarantee the accuracy, reliability, and completeness of the information. In no event shall GAF be held responsible or liable for errors or omissions in the content or for the results, damages or losses caused by or in connection with the use of or reliance on the content.

Interested in sharing or republishing our content? We kindly ask you to adhere to our guidelines.