Material and system description
Thermoplastic membranes are distinguished from thermoset materials in that there is no chemical crosslinking. These membranes can be softened by heating or hardened when cooled. Because of the materials' chemical nature, thermoplastic membranes are seamed together by heat welding with hot air tools or solvent welding.
The most common thermoplastic roof membranes are PVC and TPO. The following provides general descriptions of these two systems.
Polyvinyl Chloride (PVC)
PVC sheets are produced by cross weaving, spread coating or extruding. These sheets are typically reinforced with polyester or glass-fiber mats or scrim. PVC sheets contain plasticizers and stabilizers, as well as other additives to provide flexibility and achieve other desired physical properties to better form to the substrate. Some membranes are available with nonwoven fleece backing adhered to the underside of a sheet.
Thermoplastic Olefin (TPO)
TPO membranes are produced by calendering with lamination, extrusion with lamination, or extrusion-coating techniques. TPO sheets are a blend of polypropylene and ethylene propylene polymers and usually are reinforced with polyester. TPO sheets contain colorant, flame retardants, UV absorbers and other proprietary substances to achieve desired physical properties.
TPO membranes commonly are white due to the energy efficient qualities.
PVC and TPO roof membranes can be installed fully adhered or mechanically attached.
When purchasing a new roof system, there will be two warranties to consider. First, there will be the manufacturer's warranty. In general, these warranties cover defects in the manufacture of the roof membrane. Once the project is complete, be sure the contractor provides you with a certificate for your records.
Second, the roofing contractor will provide you with a warranty covering his workmanship. Typically, this will cover installation and related issues. The warranty should contain what items are covered and what will void them. Many contractors offer one year or two years of coverage; however, there is no industry standard.
Below are documents providing examples of TPO and PVC