dow epoxy. damn!

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#1

i got this weird thing happen on my last infusion.

first of all, im stupid, i know, i didn’t close off the resin feed, i got carried away cause the resin was infusing real slowly towards the end of the mold and as soon as it reached the end, i set the timer to my vac.pump to run for another 4 hours and left…

2 days later when i tried to demould it, the resin in the most of the product was still sticky, so i thought it must be the cold… so i left it in the mould for like…6 days. tried to demould it then, and it was still soft in most parts. the resin in the container was rock solid since day two too, so i dont know what happened in there. my first thought was that the resin uses a diffrent mix ratio than the usual 2:1, but then the resin in the feed container would be sticky too… anyway when i demoulded it, the product was soft, except some areas near the resin feed, and was also sticky ,and even wet at some points. took a lot of time to clean the mould with acetone…

any ideas?

#2

possibly incorrect mix ratio; incompatible part A and part B.

Possibly you did not stir/mix the resin for longer than 2 minutes. Epoxy is fussy if it is not mixed really well.

No other reason i can think of. besides maybe you used a waxed paper cup? no wax cups with epoxy.

#3

be sure to mix your epoxy with a digital scale accurate to the tenth of a gram, and always mix first in on container then transfer to a second and mix some more

#4

while your first thought should be towards the mixing ratios I’d also suggest trying to heat the very thin areas. I know there is a name for this but can’t think of it right now sorry

I ran into this problem with a new VER that I tried recently, the laminate was too thin and there wasn’t enough resin to heat up sufficiently and cure to its final stage.
The next part I did I added alittle heat to the mix. Just an overhead radiant heater, kept the mold and infusing part at a consistent 70deg. Everything was the same as the first attempt but this time a perfect part.

#5

how cold is it where you are? We have had situations similar on thin stuff where the epoxy left in the cup will still exotherm and cure but due to the really cold temperatures the resin which has been infused wont cure without any heat. You could leave it weeks and it would still be sticky in the workshop, try bringing it in somewhere warm.

#6

it was preety cold… around 7 degrees C, and near by is the garage door… :frowning:

i dont remember if i mixed it for 2 minutes, and i know the a and b parts are compatible cause they were given to me as a set by the company. also, the cup was glass…

all that leads me to think that it must have been the cold…or else the resin in the cup would not have cured either… next time, im trying it with a heater pointing at the back of the mould (so i dont do any damage to the bag or sumthin)

#7

not to sound crazy or anything…but…the epoxy isn’t a HEAT set epoxy is it? ie: you need to cure it at 250f, 350f, etc for it to harden?
I can imagine that some room-temp epoxies might be picky if it’s almost freezing!

#8

yeah it was the cold… i talked to the company today, they said its 2:1 , so the mixture was right… damn cold…