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The key to UltraPly TPO’s durability

A building’s roof is its first line of defense against the elements. Any discussion on building durability must therefore include the careful consideration of the roofing system.

Thermoplastic polyolefin (TPO) membranes, available in the market since the late 1990s, are one of today’s fastest-growing roofing products. However, not all TPO membranes are created equal. There are many examples of premature failure on TPO roofs which have not stood the test of time, and the market is still experiencing issues with many TPO membranes which are failing to perform after just 5 to 10 years of exposure due to an inadequate design.

Following years of product development, Elevate’s UltraPly TPO roofing membrane is based on a specific thermoplastic polyolefin polymer in which polypropylene and ethylene-propylene rubber have been properly balanced for optimum performance and compounded with UV stabilizers, heat and ozone stabilizers, and antioxidants. It contains no plasticizers, halogens, chlorine or heavy metals, making it an environmentally friendly choice. This premium formulation, which has remained unchanged since 1996, ensures the long-term performance of the roof with properties that provide excellent weathering, ozone and chemical resistance.

The DNA of a TPO membrane

TPO roofing membranes generally have three layers: the top ply, or ‘weathering layer’, which consists of a TPO compound and a weathering package that allows the membrane to resist damage and degradation from UV radiation, heat, and the elements that it will face over the course of its service life. TPO membranes with a thicker top weathering ply tend to perform better and for longer.

The scrim layer (reinforcement) is sandwiched between the top and the bottom ply. It is typically made from polyester and provides dimensional stability and physical strength (tear resistance, tensile strength, puncture resistance etc.) to the membrane.

The bottom ply provides strength, durability and weldability. It does not contain a high-weathering package.

What matters most is not the total thickness of the membrane or just the thickness over the scrim. The top weathering ply is the key component to the membrane’s weathering performance. The thicker this layer is, the better the membrane will perform.

Elevate’s UltraPly TPO is constructed in such a way that at least 40% of the top ply weathering layer is above the scrim layer (at the scrim location). This gives it outstanding weather resistance.

Heat aging and UV radiation

There are two main factors that can be most destructive to any roofing product over a long period of time: intense UV exposure and high heat from sunlight or other sources. Damage by UV radiation is the main reason for weathering and loss of mechanical properties (cracking). 

The ability of TPO roofing membranes to resist aging due to heat exposure and UV radiation is critical to their durability and is directly related to the formulation of the different layers - in particular the top ply - and the thickness of the layer over scrim. TPO membranes with appropriate protection in on the top ply will perform better. 

Heat and UV stabilizers are critical in providing weathering resistance and long-term durability. Heat stabilizers also help to resist heat degradation and the antioxidant package contributes significantly to ensure the membrane’s weldability over time.

UltraPly TPO has the right amount of heat stabilizers in its formulation, which allows it to resist heat degradation from the manufacturing process onwards. It has also undergone several heat aging (oven aging) tests and complies with the stringent heat aging requirements posed by international standards such as ASTM and EN. 

As per the latest ASTM D6878 standard, the membrane is conditioned at 116°C for 224 days and needs to retain its physical properties, such as breaking strength and elongation, by at least 90% of the value of the unaged sample. UltraPly TPO has passed this test with flying colors.

When tested as per the EN 1297 standard (artificial aging by long-term exposure to the combination of UV radiation, elevated temperature and water) UltraPly TPO meets the European Union for Technical Approval in Construction (UEAtc) requirements even after 7,500 hours, whereas the standard requirement is only 1,000 hours and the requirements for national certificate are up to 2,500 hours. The UEAtc requirements are limited at 70°C for 168 days or 80°C for 84 days, by at least 80% of the unaged sample.

In addition to a visual inspection for defects (blisters, cracks, holes, scratches, indentations, etc.) membrane samples are also tested on foldability at low temperatures (-35°C). The performance of UltraPly TPO is better than any value declared by other TPO membranes.

Performance in the real world

Yearly UV exposure levels vary a lot around the world. The performance of a roofing membrane is therefore highly dependent on geographical location.

UltraPly TPO was first installed in 1996 on a warehouse in Las Vegas (USA), in the challenging climate of the Nevada desert. Twenty-seven years later, it is still performing well, even after several years of exposure in a region with very high UV levels.

Similar success stories have been observed in Europe and Asia. Chemical and physical tests carried out 20 years after the installation of the first UltraPly TPO roof in Europe, revealed that the membrane showed no signs of cracking of crazing, and no loss of thickness.

The right chemical balance 

The durability of TPO membranes is ultimately rooted in good chemistry. Due to stringent requirements and its worldwide application, a solid formula is essential to engineer a polymer that can withstand UV weathering and heat aging, achieving the desired physical properties in the long term. The correct balance between fire retardants, antioxidants, UV stabilizers and polymer content also has an important impact on the weldability of the membrane.

Finding the right balance between all the chemical components present in a TPO roofing membrane has always been of primary concern for Elevate. With an unchanged formulation since 1996, UltraPly TPO exhibits excellent lab and real-world results, even after several decades of exposure.