Elongation and tensile strength properties are often used to promote one elastomeric coating over another. ASTM D-412 is often cited as the test method. Unfortunately, a coating may yield different properties depending on the sample shape and how fast it is pulled in the tester. What about low temperature properties? A coating that may provide satisfactory elongation in downtown Los Angeles may not be suitable for colder climates such as the Rocky Mountains. Moreover, a coating applied to a roofing substrate that is less dynamic, such as precast concrete, may perform satisfactorily, but crack badly over a light gauge metal deck roof system over widely spaced bar joists. Thus, substrate dynamics must be considered when making a prudent choice.
Mechanical properties are usually determined in the laboratory after a short drying and curing cycle. However, in the real world, the coating will still be required to have extension properties and low temperature flexibility at low service temperature after years of exposure. How flexible is the coating at low service temperature after X thousand hours of artificial or accelerated weathering? How flexible is the coating after 5-10 years of actual field weathering on a "real" roof? Plasticizers can be added to a coating to give excellent elongation and flexibility at low temperature. However, these will migrate out of the coating upon weathering and cause the coating to become brittle and possibly fail prematurely.
For Further details please visit: Elastomeric Roof Coatings
Mechanical properties are usually determined in the laboratory after a short drying and curing cycle. However, in the real world, the coating will still be required to have extension properties and low temperature flexibility at low service temperature after years of exposure. How flexible is the coating at low service temperature after X thousand hours of artificial or accelerated weathering? How flexible is the coating after 5-10 years of actual field weathering on a "real" roof? Plasticizers can be added to a coating to give excellent elongation and flexibility at low temperature. However, these will migrate out of the coating upon weathering and cause the coating to become brittle and possibly fail prematurely.
For Further details please visit: Elastomeric Roof Coatings
