Facts About TPO Formulation

We recently published a blog post on the history of TPO roofing membranes. As noted, the very first TPO roof in the United States was installed in 1986. Since that beginning, the membrane has come a long way. The ASTM specification has been strengthened many times and warranties have been extended. In fact, it’s now the largest-volume membrane in North America to the tune of over one billion square feet per year. However, some online discussions question how TPO is put together and how it really performs. Let’s take a look at some of the concerns about TPO:

 “There is no TPO on the market with a consistent formulation.”

  • The TPO polymer (the basic chemical used to manufacture TPO membranes) has remained the same since around 2000. In fact, one supplier accounts for over 90% of the polymer used by all membrane manufacturers. That material has never been changed.
  • Stabilizers are materials added to protect the TPO sheet from UV and heat exposure. Over the years, better stabilizers have become available and many membrane manufacturers have taken advantage of them.
  • I can’t speak to what other companies have done. However, at GAF, we were very pleased with our membrane performance and didn’t see the need to change the formulation. Based on lessons learned developing our EverGuard Extreme® Membrane, we added some additional stabilizers to our regular EverGuard® Membrane sheet a few years ago.

 “The warranties are really impressive, but TPO hasn’t been around long enough to know that it will last.”

  • First of all, remember the length of a product’s warranty is not a guarantee of how long the product will last, but rather how long the manufacturer’s obligations will last in the event of certain product defects covered by the warranty.
  • There is now a substantial amount of installed TPO, especially from the three manufacturers who have been supplying the material since the early 2000s (or before).
  • Roof inspections, as part of warranty and maintenance programs, show that for the most part, the membrane is holding up very well. In fact, it’s because of real-world performance that manufacturers have felt comfortable extending warranties.
  • As manufacturers understood how the membrane was performing over the past 20 years, improvements have been made:
    • Better stabilizers were added to address heat-aging concerns.
    • An improved thickness over scrim requirement was added to the ASTM D6878 TPO roofing specification. This means the weathering layer thickness specification was tightened up.

My advice when reading statements about formulation changes is to consider the following:

  • Manufacturer’s reputation – have you had consistently good results using product from the manufacturer, and does that manufacturer have a solid reputation within the industry?
  • Any product, from cars to cell phones to computers, gets improved as new technology becomes available. I’m certain that building owners expect to get the best membrane that can be made today–not formulations from decades ago.
  • Always remember that good installation is critical for the long-term performance of a roof. The membrane is important, but the installers need to be experienced with whatever membrane has been chosen.
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  1. John Lake

    I have been in the commercial roofing business for over 40 years. I have worked for both large manufacturers and small. I have spent most of my career working with the design community getting this type of material specified so I am very interested in the changes in materials. TPO and EPDM especially.

    • Thomas J Taylor, PhD

      Thanks for checking in with our site. TPO has changed over the years and continues to improve. It’s notable that the ASTM D6878 “Standard Specification for Thermoplastic Polyolefin Based Sheet Roofing” has been strengthened several times. Some of the changes include improvements to the thickness over scrim requirements and the heat aging resistance.

    • Thomas J Taylor, PhD

      Life expectancy for any roofing product depends on many factors, including location, roof design, attachment method, and local climate. For any single ply membrane, product thickness also plays a role. You might want to look at the results of a large independent TPO study. This shows how well TPO performs in controlled accelerated aging tests.

    • Thomas J Taylor, PhD

      No, I do not. But, TPO is used in surprisingly diverse applications. TPO can be made softer than the grade used for roofing, or harder. It is now used extensively in automotive interiors – which would be the closest application to what you are asking. The automotive use is very demanding – car interiors get lots of heat and light, and TPO does very well in this application. Then, if you look at the soft grip rubbery type material on some pens and toothbrush handles, those are also TPO. Thanks for checking in with us.


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