NRCA and the Midwest Roofing Contractors Association (MRCA) have conducted limited testing of polymer-modified bitumen sheet products. The tests' results show some products do not comply with applicable physical property requirements, which is cause for concern.
To conduct the tests, NRCA and MRCA obtained full rolls of uninstalled polymer-modified bitumen sheet products from roofing contractors' and distributors' warehouse stock. Sixteen products from seven manufacturers were tested; 13 of the products were SBS polymer-modified bitumen membranes, and three were APP polymer-modified bitumen membranes.
Product specimens were subjected to low-temperature flexibility and granule embedment testing by a recognized testing laboratory. Low-temperature flexibility testing was conducted before and after heating aging according to applicable ASTM International product standards' prescribed methods. Granule embedment testing was conducted in products' as-received conditions according to the product standard's prescribed methods. Test results are shown in the figure.