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Here is a phenomenon that has perplexed many new installers of poured in place rubber surfaces. You mix and trowel a new surface or you patch an existing hole and a couple days later the color of the EPDM granules you used has completely changed. You double check the color you used and sure enough it was a different color. Welcome to the ambering effect of Aromatic binders.
Polyurethane binders that are used in poured in place installations, whether it is a playground surface, a running track, or a pool deck come in two categories: Aliphatic and aliphatic binders. Aliphatic binders are clear and typically used around pools and splash pads as they are more resistant to chlorine and other chemicals. They are also. used the EPDM granules used need to keep their colors.
Aromatic binders on the other hand are the go to binders for most playground and running track applications. They are preferred for their availability, cost effectiveness (Roughly half the price of Aliphatic binders) and have great tensile strength. However, they have one big drawback that can be a nuisance at times. They are not very UV stable and tend to amber EPDM or TPV granules and even chance their color to something else altogether.
The colors that are usually affected by Aromatic binders are the following:
Click here to view samples of the colors affected by ambering
The level of ambering or yellowing caused by aromatic binders is ultimately based on how much the rubber surface is exposed to UV rays and how consistent that exposure is. A surface troweled in the morning will sustain a different level of ambering than a surface troweled in the afternoon in the same spot using the same binders and rubber granules. Moreover, if the surface is artificially shaded, through shade structures and trees will yellow differently than a surface that is not.
The ambering or yellowing effect will subside with time and as the surface is used, a phenomemon that is called "Burn back". This happens as the think film of aromatic binders sitting on top of the surface is degraded with foot traffic. All of a sudden you will notice the surface come back to its original color. A shortcut to solving the ambering issue is actually to sand that film off the top surface with a belt sander. Most installers just wait for the burn back to take its place though.
Before picking an Aromatic binder for your install or repair, make sure you understand its ambering effect. As always, if you have any questions, do not hesitate to drop me a line at hal@trassig.com
