Membrane roofs are most commonly made from synthetic rubber, thermoplastic (PVC or similar material), or modified bitumen.
This is in part due to studies being released in the 1980s to early 2000s showing the average lifespan of thermoset membranes between 15 and 20 years, although the products have undergone massive alterations since then.
The most commonly used uncured elastomers are chlorosulfonated polyethylene (CSPE), chlorinated polyethylene (CPE), polyisobutylene (PIB), nitrile butadiene polymer (NBP), although none of the products are known to be commonly used in the last decade, in part due to environmental concerns brought up regarding the chemical curing processes in the late 1990s.
During manufacture, plastics or rubbers are added to the bitumen while heating, modifying its properties to give it a higher softening point and greater elasticity.
Copolymers commonly used to modify asphalt include atactic polypropylene (APP), styrene-butadiene-styrene (SBS), styrene-butadiene rubber (SBR), and styrene-ethylene-butylene-styrene (SEBS).
First, asphalt with direct exposure to sunlight degrades much faster, mainly due to the expansion and contraction throughout a day, and also the damage created by UV rays.
Each of the newer types of membrane roofing systems contain materials that resist expansion and contraction, as well as reflect much of the UV rays.