Post curing Adtech 820

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#1

Hi Guys, How long should an infused part (Adtech 820 w/1hr hardener) be left to cure at ambient temps (50-75F here in Phx) before postcuring at Adtech’s recommended 150F for 4hrs. BTW: I was thinking a longer post cure couldnt hurt… like 24-48 hrs at 150-160F… what do you think?

Thanks in advance for the help!

#2

The stack for the part is: 3 x 5.7oz 2x2 twill CF, 1 x 5.7oz plain weave CF, 1/4" rohacell IG71 core with peforations spaced 1" apart, 1 x 5.7oz plain weave CF, 3 x 5.7oz 2x2 twill CF.

I also sprayed duratec’s VE in mold white primer before laying the first layers of CF.

The part infused beautifully… cant wait to demold to see how it turned out!

Here are some pics:

http://i1095.photobucket.com/albums/i477/jbocek/IMAG1339_zps64a824c1.jpg

http://i1095.photobucket.com/albums/i477/jbocek/IMAG1338_zpse79d03e3.jpg

http://i1095.photobucket.com/albums/i477/jbocek/IMAG1335_zps68764230.jpg

http://i1095.photobucket.com/albums/i477/jbocek/IMAG1333_zpsdda160fb.jpg

#3

Longer never hurts. Just keep in mind the ramp rate. 20F/h at maximum. So it will take a while before you reach the temperature at which you want to postcure.

Was too lazy to find the TDS, so no comments on how high or how long…

#4

Here is a link to the tech data sheet for the Adtech 820 resin.

http://www.adtechplastics.com/ADTECH_TECH_SHEETS/Marine%20Products/820%20Series%20Tech.pdf

[FONT=Arial][SIZE=2][FONT=Arial][SIZE=2][FONT=Arial][SIZE=2]“HDT testing conducted on neat resin samples post cured 4 hours at 65°C/150°F”

The TDS says minum cure is 24hrs and full cure schedule is 7 days. Does this mean I should wait 7 days before post curing or am I okay to post cure after 24hrs? Remember my ambient temps this time of year range from 50-75F.
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#5

15 to 24 hours at room temp prior to PC is a pretty common recommendation.

#6

Are you doing postcure with the part in the mold or out of the mold?
Thanks

#7

I infused the part approx three days ago (72 hrs ago) and I will be post curing in the mold. Note that the TDS of the Adtech 820 resin says “minimum cure 24hrs” and “full cure schedule in 7 days”.

#8

If I’m not wrong when you make the post cure then you will already have a full cure and no need of the 7 days .
But I’m not sure I you have to post cure in the mold

#9

A post-cure will drive the cross-linking beyond what is achievable with a room temp cure. You can typically not get the Tg above 135*F with a room temp cure for an epoxy. You can only get above that with a heat treatment.

#10

Wyo. what is the right way to postcure ?
Step 1: cure
Step 2: keep in mold and let stay for 12 to 24h
Or take out of the mold and let it for 12to 24h
Step 3: postcure in oven the part in the mold(no demold until now)
Or put back the part in the mold and postcure in the oven for the needed time

I’m trying to understand the postcure process
If we don’t take out the part from the mold after curing time then we don’t know how the part come out of the mold and we are investing more time in postcure
If anybody have some comment about this I appreciate
Thanks

#11

This Adtech stuff is another magic miracle resin:

-full cure in 7 days
-HDT 82 degrees C / 180 F (With the nice comment that this has been measured after a postcure.)

So this stuff cures fully in 7 days, but if you postcure it cures even better…

Anyhow, if you do not need the mould, keep it in as long as possible.

Postcuring can be done in mould, but make sure the mould can withstand the heat.
The other option is a freestanding postcure. In that case it is VERY important to use a conservative heat ramp rate. (10C / 20F / hour or so) or you will witness distortion.

On very fast resins you can ramp faster, on very slow systems you need to ramp even slower.

Keeping the resin at RT for 24 hours seems to be an industry standard, but I have not received a well founded explanation. Even at my 5 day course at Huntsman I asked about it. It was OK to do it that way, but as one of my customers is doing it (couple of minutes of immediate cure at 180C) is also OK…

#12

I must confess that I have deviated from the 24 hour room temp cure prior to PC. I would often ramp the temps up to 100*F and hold for 4 to 6 hours (until the resin sets) and then start the ramp up to the dwell temperature. I have witnessed and tested some resins that are more brittle if they cured too quickly.

The reasons for an initial room temp cure are:

  1. Too much heat too soon can cause the resin to exotherm badly. This will reduce it’s properties
  2. In open hand layups the added heat will reduce the viscosity of the resin. This can enable the layup to fall off the mold, pull way from tight corners, allow compressed fibers to rebound and pull in air.
  3. In theory, you want the polymer/resin to develop a very organized molecular lattice/structure. This reduces matrix stress and increases strength, stiffness, and HDT. If a resin cures to quickly the molecular lattice is less organized. This is all theory though.
  4. Many resins will have higher shrinkage if they are cured too quickly.

As herman already stated, try to cure the part in the mold. You will typically get less print-thru if you fully cure the part in the mold. Print-thru is a common issue with a free-standing post-cure or demolding the part without a complete resin cure.

#13

So what is basicly better? curing right after infusion or post curing next day?

#14

Such popular problem but seems taboo