Evaluation of In-Service Thermoplastic Olefin (TPO) Roofing Membranes

As part of a five-year investigation, mechanical (strength and elongation) and chemical (thermogravimetry and dynamic mechanical analysis) methods of evaluation are used in this paper to characterize in-service thermoplastic olefin (TPO) roof membranes. All the non-reinforced membranes meet the minimum thickness and tensile strength requirement as specified in the proposed ASTM standard. The polyester scrim reinforced membranes had higher tensile strength and elongation values than those reinforced with random mat of short glass fibers. The standard should consider defining the breaking strength in terms of “stress” instead of load and incorporating strain energy requirements at 23 °C and -40 °C. The term TPO is confusing and very vague and the standard should consider differentiating between the different types of TPOs. Based on thermogravimetry, at least four different types of TPOs are currently in service. Lastly, the standard should consider using the glass transition temperature to monitor changes in membranes due to aging/weathering.