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June 14, 2019
Summer is here! Along with weather suitable for visits to beaches, lakes and swimming pools comes heat and humidity! Increased heat and humidity can affect how many of our products, and similar products, cure. So let’s go over what to expect when working with AeroMarine Products’ various products in a hot and/or humid environment.
Epoxy is exothermic, meaning it generates heat as part of its curing process. Our epoxies (excluding the aptly named 5 Minute Epoxy) usually cure in 24 hours at 70F. If the ambient temperature is over 70F, it will decrease the work life of the epoxy and shorten the cure time. The best way to avoid the epoxy gelling up while you are still trying to work with it is 1. Keep the containers of epoxy and hardener stored in a cool area, out of direct sunlight and 2. Mix smaller batches of epoxy. Containers of epoxy/hardener that are already warmed up are going to start curing MUCH more quickly once mixed. Smaller quantities of epoxy generate less exothermic reaction and thus less heat, keeping the epoxy from curing too fast.
Humidity doesn’t affect epoxy. However, if the epoxy gets wet before it cures, it can develop white spots. If you’re working with the epoxy in an outdoor setting, check the weather for rain and the dew point to ensure your epoxy stays dry through the curing process.
Urethane is also exothermic, so if it is over 70F, proceed with caution and mix small batches. Alternatively, find an air conditioned space to mix and pour your urethane. Humidity is the real problem when working with urethane in the summer. All urethanes, from expanding foams to casting resins and everything in between, are EXTREMELY sensitive to moisture before curing. Humidity higher than 50% will cause bubbles in urethane resins as well as overblown cells and brittleness in urethane foams. If you open a container of urethane in a humid environment, the humid air will contaminate and ruin the entire container. So please, no working with urethanes when the humidity is over 50%.
The biggest issue with silicone and the summer heat is leaving or storing containers of uncured silicone in a hot environment, such as a car or outdoor shed. Exposure to extreme heat (100F+) can degrade the quality of the uncured silicone. So don’t stop by AeroMarine Products on your lunch break and then leave your silicone kit in the car until the end of the day, please.
Platinum catalyzed silicone, like our Food Grade Silicone, High-Temp Silicone and Silicone Putty, aren’t affected by heat or humidity in their cure process.
Tin catalyzed silicone, like our 128 Silicone and 125 Silicone, are affected by humidity. Humidity will shorten the cure time of a tin catalyzed silicone but not so much the work life. In a humid environment, pot life stays about the same while the cure time can be shortened by several hours.
The best practice is to store uncured latex in a room temperature environment, 68F to 72F. The same is true for your cured latex molds, which are much more sensitive to heat than the uncured latex. Latex molds can be destroyed by storing them in extreme (over 90F) heat. So, please keep your latex molds in a cooler location. Generally, latex cures just fine in a hot and/or humid environment. The heat can cause latex to cure a little faster while the humidity can slow down the cure process a bit.
If you have any questions about this topic or any other, give us a call, 877-342-8860, or drop us an email at [email protected]. Have a great, project filled summer!