August 11 - August 16, 2010
Is there a definitive relationship between mechanical properties of coatings (such as elongation and tensile strength) and crack-bridging capability?
Adam Backhaut of Diamond Vogel Paints on
November 23, 2010:
Coatings are formulated with different technologies, such as alkyds, polyols, acrylics, epoxies, etc. Each resin system has different wavelengths and flexibility properties. Technologies are formulated for specific performance. Some coatings may be very flexible but not durable, and some may be rigid and durable, etc… Flexibility and tensile strength may not always correlate the durability or mechanical properties of the coating. Chances are, if the coating fails right way, the material was not designed for the application. It is important to understand the use of the product so the proper materials are used, which will help the long-term durability of the substrate.
Bart Wilbanks of CPS Color on
August 12, 2010:
No. Coatings having both great and poor mechanical properties can bridge a surface crack in the substrate. This ability has litte dependence on elongation and tensile strength, but relates more to the flow and leveling during the film formation. However, the bridge's ability to sustain will depend on the elongation and tensile strength of the coating.
Subrahmanya S of Asian Paints Ltd on
August 11, 2010:
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Yes, both these properties have a relationship with the crack-bridging ability of a coating. Development of a crack is due to both internal and external stress developed in the coating. If the total stress developed, which is very difficult to know, is less than tensile strength, then chances of crack development are very minimal. On the other hand, if the coating maintains its elongation (should be very high number) during its service life, then the crack bridging ability will be good.
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