One of my readers sent me a message to ask about a phenomenon he has been facing with some EPDM products, that we could call RAINBOW EFFECT or irisdesence, appearing after 2-3 days or more, exposed to light, after installation. Properties or function is not affected. It’s only a visual light diffraction with an unwanted cosmetic effects.
The phenomenon is more frequent in injection molded parts that in our top flooring materials and it’s difficult to show it on a photo, specially of a rubber flooring, I could not find one that gives a good idea of the phenomenon, so the ones attached here are only to understand the effect on other surfaces or products also producing diffracted rainbow images.
The question from my reader was if this effect is coming from paraffin oils or the Carbon Black on the EPDM mixture or what else, and also how to fixt it.
There are three potential reasons for this on flooring applications, according to my previous experiences:
- Use of some smoothing agents during installation as Diesel; Petrol or others having some kind of oil. The smoothing agent is used to avoid sticking granules to the tools and I always recommend not to use diesel for this. Whenever I’ve seen rainbow effect it was always due to the use of diesel for this function.
- Presence of some oils on the EPDM mixture that bleed or leach outside due to UV effects after installation.
- Carbon black filler bleeding or blooming (migration to the surface).
Vulcanized articles may exhibit bloom depending on the specific curing agent chosen but numerous phases of the fabrication process including formulations, methods of compounding and methods and conditions of curing can also influence blooming.
When the problem is due to the use of Diesel as Smoothing Agent , the best solution is try a cleaning by moderate pressure water with some soap as dish cleaner.
When is bleeding or blooming from some components of the EPDM mixture cleaning may be not effective and only abrading away the surface physically can the effect be removed. Some solvents as methylene chloride may remove the problem temporarily but not in a permanent way.
Take care
Rubberman Blog 