Thermoplastic single-ply membranes, such as polyvinyl chloride (PVC) typically have no chemical cross-linking in the molecular composition. Because of this, thermoplastic roofing sheets are typically seamed together by heat-welding with hot air. PVC polymers were originally produced in Germany in the 1950’s. The sheets are usually white but can be formulated in a range of colors. Typical thicknesses are 36 mils, 45 mils, 60 mils, 72 mils, and 90 mils. PVC installations may be ballasted, mechanically attached or fully adhered to approved substrates.
Thermoplastic polyolefin (TPO) membranes are compounded from a blend of polypropylene and ethylene-propylene rubber polymers. TPO membranes from various manufacturers vary in look, feel, and physical properties. TPO membranes are typically reinforced with polyester scrim or fabric that is positioned during manufacturing near the middle of the finished thickness of the TPO membrane. Seams are hot air welded. The sheets are produced as white sheets though other colors are available. Thicknesses include 45 mils, 60 mils, 72 mils, 80 mils and 90 mils. TPO installations may be ballasted, mechanically fastened or fully adhered to approved substrates.