Tuesday, October 23, 2012

EPDM Ambient Curing Systems

The industry has been trying to develop a cure mechanism that would make it possible to crosslink EPDM polymers at ambient temperature for some time.   One such polymer became commercially available in 1990 resulting in the development of EPDM Liquid Rubber as a commercial product. 
The chemistry in the liquid version is substantially similar to that of the EPDM single ply sheet.  A pendant group grafted to the polymer chain and the cure mechanism are the major differences.
The cure mechanism in the EPDM Liquid Rubber can be described as a free radical initiated polymerization.  Organic peroxide was chosen as the catalyst because it produced the best cured properties as well as a long pot life after mixing.

Cured films of EPDM Liquid Rubber have excellent weatherability, are not thermoplastic, can withstand high temperatures (up to 300° F), remain flexible at very low temperatures (brittle point is –62° F), have resistance to acids, alkali’s and polar solvents, and can withstand total water immersion indefinitely. Compatibility and performance should be the main criteria in choosing a liquid coating.  The following comparison lists the pros and cons of various types.