Thermoplastic materials are distinguished from thermoset materials in that there is no chemical crosslinking. Thermoplastic membranes can be repeatedly softened by heating or hardened when cooled. Because of their chemical nature, thermoplastic membranes are typically seamed by heat welding with hot air or solvent welding.
These are the common subcategories of thermoplastic roof membranes:
- Polyvinyl Chloride (PVC)
- PVC Alloys or Compounded Thermoplastics
- Copolymer Alloy (CPA)
- Ethylene Interpolymer (EIP)
- Nitrile Alloys (NBP)
- Tripolymer Alloy (TPA)
- Thermoplastic Olefin (TPO)
- Chlorinated Polyethylene (CPE)
The most common thermoplastic roof membranes are PVC and TPO. The following provides general descriptions of these two systems.