Parts getting soft in sun

Well I thought I was doing well with building infused parts till my new black panels hit the sun. Im using epoxy and have been infusing in a room at 80 degrees and per huntsman I thought it was fully cured in 3 days but I guess I’m wrong.i put a hood in the sun and noticed print and rubber like feel but when it cools down its like nothing even happens still looks nice. Will it cure or stay soft in sun?

You’ll be surprised how much heat a black part retains when left out in the sun . Try hitting them with a temp gun next time you feel that and see if you’re near Glass Transition Temperature, or Tg. Then compare what you find to the resin specs on the label from Huntsman . Other reasons to watch for could be , improper mixed amounts comparing volume instead of weight, or needing a post cure with temps ramped up/down .

Example:
CURE SCHEDULE:
3 to 5 days at room temperature or gel at room temperature plus 3 to 5 hours at 125F (52C).

Td on huntman says 167 and the part was at 155 in sun. Will it get more ridged as the part cures in sun?

It depend which TG they write down in their datasheet. TG on, TG1 or TG2.

After doing some research it seems that building parts that are in full sun that get hot seem to be more prone to my problem. Without an autoclave oven it seems maybe I should consider a vinylester vs an epoxy. Any thoughts on infusioning vinylesters?

you don’t need an autoclave, a simple oven is enough. Infusion vinylesters are sensitive for their mekp activators, and I never used/seen a clear vinylester.

Problem is im doing full size car parts hood ect so id need a huge oven. per huntman there 8601 is not very frendly in sun and can get to a rubber state that I witnessed he reccommed 8604 with a tg of 167 so im going to try that. btw the tg on 8601 says its tg 167 also but tech from huntman said that is not a good number so I don’t know what the hell to think but try something different.

If you are going to use Vinyl is not bad but you have to be carefull what vinyl type you will buy. Depending the quality of vinyl you can have a very good results without using oven and strong enough for your parts. You can use vinyl for 140 or 180C temperature heating resistance. Is one of the best way to create strong parts if you don’t have Oven for curring!!!