Recently, ASTM International's task force responsible for maintaining and revising the U.S. product standard for TPO single-ply roof membranes has been discussing more expeditious testing and exploring some useful differentiation among TPO membrane products.
The U.S. product standard for TPO roof membranes is ASTM D6878, "Standard Specification for Thermoplastic Polyolefin Based Sheet Roofing." ASTM D6878 originally was published in 2003 based on 45-mil-thick products. ASTM D6878 has been revised several times since its original publication, and the current edition is ASTM D6878-13, which was published in 2013.
ASTM D6878-11 (and -11a) represented a significant upgrade from the previous editions by including an increase in the minimum allowable thickness over scrim from 12 mils to 15 mils. Also, the duration of test specimen heat aging before aged physical property testing increased from 28 days at 240 F to 224 days at 240 F.