Dear users,

I'm currently working with multiple epoxy resins, but after curing on ambient temperature, i can't determine which one is A-stage and which one is B-stage, which is very important.
The B-stage epoxy only partially cures and this one needs to be cured a second time to gain full conversion.

Now my question is, how do i determine which one is the B-stage? i have a lot of material all over the place and it isn't really pointing itself out.

Thanks in advance,

Frenk

Not exactly sure what you mean, but EVERY epoxy resin benefits when post-cured at elevated temperatures. Even when the manufacturer claims a certain resin is "cold-curing", heating the part to a temperature near its Tg never hurts and always improves mechanical properties. Just do it.

The easiest way to determine whether a resin is fully cured or not is probably measuring its glass transition temperature, but this is certainly not doable by Joe Average. It's a relative easy and fast analytic procedure when you have the right equipment (which unfortunately costs a lot of money).
https://en.wikipedia.org/wiki/Differential_thermal_analysis
https://en.wikipedia.org/wiki/Differential_scanning_calorimetry

That's why I said just give the part the proper post cure treatment to be on the safe side.

a good way of telling if a part is properly cured is the sound it makes, a fully cured epoxy carbonfiber part will make a ceramic sound, a part that is not properly cured will make a dull sound

Matthieu Libeert
Founder MAT2 Composites X Sports
website: www.mat2composites.com

Thanks guys,

The problem is the "A stage" etc method of describing cure is different for each resin and also confusingly it is referred to differently in some circles to mean a different level of cure to what is described here and elsewhere.

Often it can be better to use more descriptive phrases such as "tacky but firm" "demouldable" "fully cured" etc as the meanings are easier to understand and explain.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant