Welding performance on TPO membranes

TPO (Thermoplastic Polyolefin) roofing membranes are one of the fastest growing single-ply roofing membranes available on the market today. However, not all TPO membranes are created equal. Every manufacturer makes their own version of TPO, with a different formulation, product design and manufacturing process. As a consequence, the quality of the final product and its performance vary a lot. Engineering the right polymer is the base that allows all the other elements that go into the TPO formula to work together and achieve the desired result. 

Weldability refers to the ability of TPO roofing membranes to form strong and durable seams through heat fusion techniques. This characteristic plays a pivotal role in ensuring the integrity and longevity of the roofing system, making it crucial for architects, contractors, and building owners alike. 

A common misconception is that proper welding is just about setting up the welding equipment correctly. While it is crucial to have the correct welding equipment, power supply and right temperature setting to achieve a good quality weld, the performance and ease of welding also depend on other factors. 

The welding performance of a TPO roofing membrane is highly dependent on how it is constructed. Most TPO membranes have 3 layers, each created differently. Firstly, a top ply or “weathering layer” which is exposed to UV radiation, heat, and the elements that the membrane will face during its service life. Then there is the scrim layer, a reinforcement that provides dimensional stability and physical strength. Finally, the bottom ply provides strength and durability, playing a key role in the weldability. 

In order to achieve a good welding window and make the membrane easy to weld, the right balance between the formulation of the top and bottom ply is crucial. If that balance is not right, the difference between welding setting requirements for top and bottom ply could be far apart, which could in turn narrow the welding window.

The thickness of the top and bottom ply also plays an important role in the welding performance. When welding two adjacent TPO membranes to make a seam, this is done between one membrane’s top layer and the other’s bottom layer. If one or the other does not have the sufficient thickness, it will not be easy to weld the membranes together. Moreover, the strength of the weld will depend on the strength of the thinner, weaker layer.

The welding aspect of Elevate’s UltraPly TPO roofing membrane is taken into consideration in its formulation. It is designed to offer a wide welding window, contributing to its ease of installation by allowing the roofing contractor to complete hot air welds consistently in a broad temperature range.

Welding is further improved by the fact that at least 40% of the top ply layer of UltraPly TPO is located above the scrim layer (at the scrim location), which provides outstanding weather resistance to the membrane, enhancing the durability and performance of the whole roofing system. Even after many years of exposure, the membrane remains easy to weld.