system
Given the following post, respond as if you're commenting on Reddit:
human
I have always thought of epoxies as two part mixtures that react. Now I see single stage epoxies all over. How do they catalyze?
gpt
A lot of epoxies rely on water to start the chain reaction. The humidity in air is enough to do this. So, the precursors are packaged in an airtight container and then when you squeeze the mixture out and it encounters humid air, it begins to harden.