WHY DOES EPOXY HAVE AN OPEN TIME?

Amine Blush

Epoxies like Sika® MB and Sika® MB Redline are typically two part epoxy resins, and 100% solids. The curing agent (called hardener) reacts with moisture and carbon dioxide in the atmosphere in order to create something called an amine blush. This blush will result in a waxy usually invisible layer and will determine the limits of your open time. In worst case scenarios, a white/yellow layer will be visible on top of the epoxy.

WHAT ARE THE RISKS?

The blush will create an oily and sticky surface possibility resulting in several issues:

  • Transfer to the second coat
  • Delamination as the amine blush will work as a bond breaker

  • Difficulty in re-coating
  • Water spotting
WHAT SHOULD YOU DO IF YOUR OPEN TIME EXPIRES?
Step 1:
Lightly sand the epoxy to provide a good texture.

Lightly sand the epoxy to provide a good texture.

Step 2:
Clean contaminated surface with approved solvent such as acetone, MEK or Xylene.



Clean contaminated surface with approved solvent such as acetone, MEK or Xylene.

Step 3:
Allow all solvent wipe residues to completely evaporate, flash off and dry before the next step.


Allow all solvent wipe residues to completely evaporate, flash off and dry before the next step.

WEATHER CONDITIONS
  • Cool, humid conditions are the biggest concern. The cold weather will slow the reaction; in addition the humidity will give perfect condition for faster development of amine blush.
  • In warmer weather where the curing cycle is shortened, amine blushing tends to happen more inconsistently.