PVC (polyvinyl chloride) and CPA (a polyvinyl chloride & acrylic resin alloy) are two of the most common thermoplastic, single ply, roof system membranes.

The sheet is usually a woven polyester fabric coated with a blend of thermoplastic materials to form a flexible sheet ranging from 35 to 60 (depending on manufacturer) mills thick and is hot air or solvent welded at the seams.

When Thermoplastic roof systems were first introduced in this country some manufacturers, in an effort to be competitive, eliminated the scrim which helped control shrinkage and distributed stress. Also some of the manufacturer’s formulation for their sheets was not quite right leading to product failures that gave thermoplastics a bad name. This was particularly true at altitudes, such as the Front Range, where degradation from the UV’s is more common in this material.

However, the roofing industry as a whole has addressed and corrected these problems and thermoplastics have a significant market share.Thermoplastics tend to be high end roof systems and are more often a new construction application.  Click here for technical information.

PVC and TPO roof membranes can be installed fully adhered, mechanically attached or ballasted. Most PVC and TPO membranes do not receive surfacing.  Is a TPO Roofing System the type of roof that you need?

For more information please call our roofing professionals at (303) 971-0256 or Click Here to request a free quote.

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Material and System Description

Thermoplastic materials are distinguished from thermoset materials in that there is no chemical cross-linking. These membranes can be repeatedly softened by heating or hardened when cooled. Because of the materials’ chemical nature, thermoplastic membranes typically are seamed by heat welding with hot air or solvent welding.

There are five 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.

PVC sheets are produced by calendaring, spread coating or extruding, and typically are reinforced with polyester or glass-fiber mats or scrim. PVC sheets contain plasticizers and stabilizers, as well as other additives to impart flexibility and achieve other desired physical properties. Some membranes are available with non-woven fleece backing adhered to the underside of a sheet.

  • Sheet widths range from 6 feet to 12 feet wide.
  • Sheets are typically 45 mils to 90 mils thick.
  • Seams are sealed by heat or chemical welding.
  • PVC membranes are produced in numerous colors, though gray and white are the most common.
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.

  • Sheet widths range from 6 feet to 12 feet wide
  • Sheets are typically 40 mils to 100 mils thick
  • Seams are sealed by heat welded with hot air
  • TPO membranes commonly are white or black