Polyisobutylene is a synthetic rubber, or elastomer, that was first developed in Germany in the 1930s. It is special because it is the only rubber that is gas impermeable, that is, it is the only rubber which can hold air for long periods of time. It is categorized as an extruded plastomer which is a material that processes like thermoplastics but with rubber properties, requires no vulcanization, is elastic and most importantly, retains flexibility at low temperatures.

PIB is typically a sixty mil (.060") membrane. The backside is laminated with a forty mil (.040") rot-proof polyester fleece backing providing a total thickness of one-hundred mils (.100"); this provides a breaking strength that is up to three times that of the sixty mil membrane by itself. PIB is available in either black or white and has excellent resistance to weathering, ultraviolet light, sparks, radiant heat, and gases from industrial plants. It comes with a two inch (2") self-sealing edge that offers excellent seam strength.

PIB is installed using either hot asphalt or cold process adhesives. The adherent only partially penetrates the fleece backing leaving the PIB membrane free or "floating" on top of the fleece, therefore chemically and physically unaffected. This also allows the remaining portion of the fleece backing to act as a vapor equalization layer which can eliminate blister development and entrapped moisture. One of the most significant features is the self-sealing edge. It not only provides an excellent waterproof system but it also acts as an expansion joint to relieve stress between the roof membrane and the substrate.

PROS

• Can be installed with cold-process adhesives or asphalt
• No ballast necessary
• Available black or white
• Longevity
• Weather, sparks, heat, and ultraviolet radiation resistant
• Complies with FM I-90 and UL Class A listings
• Simple seam details
• Excellent performance at wide temperature ranges - no shrinkage
• 10 year labor and material warranty

CONS

• Not resistant to organic solvents such as benzine, toluene, or petroleum
• Not resistant to materials containing solvents such as lacquers, fats, and oils
• Bird droppings can present problems

ROOF MAINTENANCE

1. Keep all drain details functioning.
2. Repair any damage to the membrane as soon as it's noticed.
3. Keep all foreign debris from the roof surface.
4. Trim back any overhanging branches.
5. Minimize foot traffic. Install traffic protection pads in areas where heavy traffic occurs.