Thermoplastic roof membranes have been in use on commercial, industrial, institutional and governmental facilities for more than 25 years in the United States. The benefit of a welded lap (either by hot air or chemical) was recognized long ago as the superior feature of a thermoplastic membrane. We learned that unreinforced thermoplastic (such as plain PVC) did not give long-term performance when compared to reinforced PVC. There are a number of coated fabric products in use today that have PVC (or other thermoplastics) as the principal polymer present. They all, in one form or another, have a formulation that works. The first concern was performance; cost took a back seat for several of these products.
Today we have thermoplastic polyolefin (TPO) available, all reinforced. TPOs can demonstrate near EPDM-like resistance to weathering change if formulated and manufactured in a responsible manner. Unfortunately, cost cutting has set in, leaving performance to be assumed. The physical properties of TPO membranes can vary significantly with the type and amount of filler, fire retardants and UV stabilizers. We still do not have any ASTM standard on TPO roof membranes, due in part to the varied formulations that are possible.