SpecTopics: TPO Impact Resistance Tests
Impact resistance requirements in Thermoplastic Polyolefin (TPO) roofing specifications generally mention that the membrane needs to resist impact damage when tested according to ASTM D3746, ASTM D4272, or the "Resistance to Foot Traffic Test" in FM Approval 4470.
Two out of the three referenced standards are not applicable to TPO roofing membrane. Let’s break down the standards.
ASTM D3746-85 (2022) "Standard Test Method for Impact Resistance of Bituminous Roofing Systems"
This test method covers the determination of the resistance of bituminous roofing systems to impact loads at any desired temperature, with a missile of the weight, size, and shape specified within the ASTM testing standard.
ASTM D4272-15 "Standard Test Method for Total Energy Impact of Plastic Films by Dart Drop"
This test method describes the determination of the total energy impact of plastic films by measuring the kinetic energy lost by a free-falling dart that passes through the film.
Both of these test methods use other materials which may be in part similar – bituminous roofing is roofing, as in the first standard and TPO membrane is a plastic sheet (but not really a film) as in the second standard. However, neither gives the results of impact resistance as compared to other single-ply membranes.
ASTM D6878/D6878M-13 "Standard Specification for Thermoplastic Polyolefin Based Sheet Roofing" is the correct standard.
This specification covers flexible sheets made from TPO as the principal polymer, intended for use in single-ply roofing membranes exposed to the weather. The sheet shall contain reinforcing fabrics or scrims. As the parent or main standard, it contains other test references within, including ASTM D2137-11 "Standard Test Methods for Rubber Property - Brittleness Point of Flexible Polymers and Coated Fabrics". TPO membrane impact resistance is tested per ASTM D2137, Method B. This test subjects TPO membrane to impacts at low temperatures. Carlisle TPO membrane meets the requirements in ASTM D6878 which requires no cracking upon impact at -40° F. In fact, Carlisle’s TPO will typically withstand impact at temperatures as low as -50° F. This is stated on the Carlisle TPO Membrane Product Data Sheet.
Sure-Weld® TPO is FM Approved, and all FM Approved assemblies have been tested to pass FM 4470 for foot traffic resistance.
To learn more about the results of the ASTM D2137 test for Carlisle SynTec Systems’ TPO roofing membrane, refer to the Product Data Sheets on the Carlisle website or click here and look for the typical properties and characteristics table on page 4.
If you have any questions regarding impact resistance, please contact Craig Tyler.
Two out of the three referenced standards are not applicable to TPO roofing membrane. Let’s break down the standards.
ASTM D3746-85 (2022) "Standard Test Method for Impact Resistance of Bituminous Roofing Systems"
This test method covers the determination of the resistance of bituminous roofing systems to impact loads at any desired temperature, with a missile of the weight, size, and shape specified within the ASTM testing standard.
ASTM D4272-15 "Standard Test Method for Total Energy Impact of Plastic Films by Dart Drop"
This test method describes the determination of the total energy impact of plastic films by measuring the kinetic energy lost by a free-falling dart that passes through the film.
Both of these test methods use other materials which may be in part similar – bituminous roofing is roofing, as in the first standard and TPO membrane is a plastic sheet (but not really a film) as in the second standard. However, neither gives the results of impact resistance as compared to other single-ply membranes.
ASTM D6878/D6878M-13 "Standard Specification for Thermoplastic Polyolefin Based Sheet Roofing" is the correct standard.
This specification covers flexible sheets made from TPO as the principal polymer, intended for use in single-ply roofing membranes exposed to the weather. The sheet shall contain reinforcing fabrics or scrims. As the parent or main standard, it contains other test references within, including ASTM D2137-11 "Standard Test Methods for Rubber Property - Brittleness Point of Flexible Polymers and Coated Fabrics". TPO membrane impact resistance is tested per ASTM D2137, Method B. This test subjects TPO membrane to impacts at low temperatures. Carlisle TPO membrane meets the requirements in ASTM D6878 which requires no cracking upon impact at -40° F. In fact, Carlisle’s TPO will typically withstand impact at temperatures as low as -50° F. This is stated on the Carlisle TPO Membrane Product Data Sheet.
Sure-Weld® TPO is FM Approved, and all FM Approved assemblies have been tested to pass FM 4470 for foot traffic resistance.
To learn more about the results of the ASTM D2137 test for Carlisle SynTec Systems’ TPO roofing membrane, refer to the Product Data Sheets on the Carlisle website or click here and look for the typical properties and characteristics table on page 4.
If you have any questions regarding impact resistance, please contact Craig Tyler.
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