Epoxy curing question

hello all

i have been lead to believe that heating epoxy (once it has been laid up) not only makes the cure faster but also makes the finished matrix stronger?

is this true? and is there any literature to help me with this.

from what can find on-line quickly it only really makes it cure faster?

cheers

 

Something here (thou the original question was about prepregs)
http://www.boatdesign.net/forums/fiberglass-composite-boat-building/post-curing-epoxy-52184.html

 

Epoxy has an exothermic reaction which creates heat and helps it cure. Warming it up a few degrees will hasten it's curing. There are different formulations for different temperature ranges... The cold hardener will cure almost before you can use it in summer temperatures and the warm hardener will take forever and a day to cure in 35-40 degree temperatures. A large mix of epoxy in warm weather can actually start smoking it is so hot. Epoxy also softens at a relatively low temperature so heating it excessively is not wise either. As to making it stronger... I expect it simply exhibits it's full strength sooner because it cures fully sooner if warmed up.

 

Accelerating the cure with modest heat, on room temperature cure formulations doesn't make the cured matrix any stronger or stiffer. The additional heat just speeds up the cure. The chemical reaction is dependent on the resin hardener formulation for it's physical qualities and heat hasn't anything to do with it. Simply put, the molecular reassembly and their bonds, will occur regardless of temperature (unless too cold), based on resin/hardener ratios and the materials within only.

 

Postcure.

http://www.systemthree.com/sys3news/technicalresources/postcuring/

You should contact your resin supplier before attempting a true " post cure "

Common general purpose epoxy is formulated to achieve good mechanical properties at room temp. Post cure epoxies are special purpose and , designed to be heat cured .

Normal workshop postcure for general purpose epoxy is always good. This post cure is non technical, low temp and could mean rolling your skiff out of the garage into the sun then covering with a black plastic sheet to raise the temp to 120 f . Im sure it increases the mechanical properties , but more important it post cures all the variuos epoxy resins and fillers on your hull and helps prevent future print thru . After this black plastic post cure you bring the boat back into the shop...sand flat and paint.