in mold clear compatibility with release agent

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#1

Hey all,
I’m trying out the in mold clear method using a 2k automotive clear which is sitting above frekote 770 semi perm. I’m getting some beading in areas though. it appears that if I really hit it hard with a thick and heavy coat, it doesn’t bead up, but medium coats for whatever reason are able to.

has anyone ever experienced this? is 2k paint even supposed to bead with a semi perm? I saw wyomings video and he seemed to have an easy enough time applying it after a wipe down with semi perm.

I would imagine the best way to apply it would be one ultra light coat at first that can flash nearly instantly - this would be the contact coat with the frekote semi perm release - and then whatever (light to heavy) coats afterwards since there is no contact anyways. is this correct? I haven’t had time to experiment with this yet though.

Thanks in advance!

#2

Hi
I paint all my planes in mold with 2k. I use marbocote and chemrelease semi perminants.

By far the best way is as described. Fine dust coat , and then follow up with thicker coat etc.
Also one thing to try is wax over the semi. Doing this gives the paint something to bite to and reduces fish eyeing or beeding. I done this with marbocote , but I don’t need to do it with chemrelease.

Tim

gizmo 36 glider

#3

I agree with Tim. Use a silicon -free wax.

#4

Thanks for the advice! I’ll put a layer of Meguairs #8 and see how that works (I’m assuming that’s silicone free, right? their product page doesn’t say but I’ve used it with PE before so I’m guessing it is).

Anyways, I pulled some the IMC test parts today. I did 3 panels each, all laminates are impregnated out of mold;

  1. part with a .6 oz/yd FG veil that I also wet out with epoxy in the mold before laying the laminates down

  2. part with a .6 oz/yd FG veil, NO surface wet out (surface between IMC and laminate stack)

  3. straight carbon part. for this part, I wet out half the mold with epoxy before introducing the stack and the top half was dry; the laminate was laid directly on top of the IMC.

Here’s a photo. What are the white chalky lines between the weave patterns? Are those air gaps between the fiber partern and the clear coat?

https://skydrive.live.com/redir?resid=7B9E18E26BA7C866!3935&authkey=!AEWvIKeWGh16iAE&v=3


WP_20131018_001 by redalert1031tx, on Flickr


WP_20131018_002 by redalert1031tx, on Flickr

Will sanding take care of it or will I just burn through the IMC layer into the voids?

#5

To answer my own question, sanding will just burn through it and open up the air voids. The gaps between the weaves are still there, deep as ever. I’m thinking I might be using too little resin, and too much of it is getting wicked away by my breather.

I used a P6/P31 perf release film (very widely spaced pores) and it worked well but then I got too much resin build up in corners where the hole pattern didn’t match up with the very tight radius curves so using it isn’t possible.

I’m thinking the next step is to just crazy over saturate the laminate stack and hope for the best. I just ran some numbers and it turns out, for a 1.2:1 fiber to resin ratio I need to be using about 100 mL of resin per part instead of the 80 mL I’ve been using, so hopefully that’ll improve the situation

I’m using strechlon so reducing vacuum isn’t an option either :confused:

#6

It does look like the backing is sucking out to much resin. Either way it is very even across the laminate. So I agree try more resin , roll it very well with fabric roller , and back off vaccum a little.

Tim

#7

sounds like the same problem im haveing in the air bubble/voids post… we cut out the 3/4 oz veil and the voids were still there with -24 vac but it was better then with the veil sinve the air was trapped between the two layers… we had a 1.15 to 1 ration and upped our resin as well… It helped but still now where I want to be… I was told to lower my vac after my initial deep pull… ( large vac will make any air voids larger… less vac will make smaller voids… ) kind of a strange way to think but with less air in the mould the bigger the bubble is… The whole pressure thing…

keep posting if you get it dialed in…

#8

Had another round where we upped the resin fraction significantly, and while things did look better there are still voids between the IMC and the fabric twills.

Midwest, how long do you run your part under full vacuum (or at least as full of a vacuum as your pump can get you to - mine can’t get us very far :/) before reducing vacuum back to shrink down the enlarged air bubbles?

What’s the upper limit of low pressure (the reduced vacuum pull) that you can/should run at for the curing stage after debulking the reinforcements at high vacuum?

#9

What are the minimum and maximum recoat times on the clear coat?
Are you degassing the resin?
Has the resin been thinned? i.e. Does it have high solvent content?
Why are you wetting out the cloth out of mould?
Are you consolidating the laminate stack before bagging?
How much vacuum?
Gel time?
Time under vacuum?

#10

What are the minimum and maximum recoat times on the clear coat?
Im using a fast activator and when I set up the bag with the laminates, its not tacky at all anymore. the one I made yesterday was allowed to cure for 2 hours in the sun (molds are black so they got up to 100f)

Are you degassing the resin?
Yes, but to be fair my vacuum pump has seen better days so it never pulls a ‘full’ vacuum

Has the resin been thinned? i.e. Does it have high solvent content?
no, but it is a very thin resin - sp115

Why are you wetting out the cloth out of mould?
this is more of a production thing - it is much faster for me to do the main wet out outside of the mold, lay the laminates up, and then do some extra wetting out inside of the mold

Are you consolidating the laminate stack before bagging?
I’m not sure what you mean by this. I am laying up multiple dry plies of fabric and then wetting them all out on a flat surface all in one go, and then laying them into the contours of the mold. i’m insuring that the resin soaks through, or at least the best I can. the ‘bottom’ of the laminate stack appears to be as wet out as the top when I do this

How much vacuum?
honestly I don’t have a proper gauge so I can’t tell you specifically but it’s definitely not a full vacuum. one of my problems is that i’m using stretchlon so I have to have some amount of vacuum, otherwise the bag doesn’t full compress corners down.

Gel time?
no gel time, essentially immediately after wet out (10-20 minutes) I set it up in the bag and pull a vacuum

Time under vacuum?
quite a bit, i’m working outside in very variable weather conditions so I usually let it sit under vacuum for hours to insure a decent cure before shutting the pump off, at which point it immediately goes to atmos. pressure (stretchlon… can’t hold a vacuum worth garbage)

I really want to go the wet lay and bagging method to work but at this point i’m considering trying a vacuum run. trying to get my hands on some mti hose but for right now i’m going to settle with the old school spiral and single point draw method

Chetan

#11

since we are doing a wet layup and then putting our cloth in the mold we are not degassing… We get air in the epoxy from working it in the cloth…

our cps is 650… you said your is sp115 Whats that?? Im familiar with cps… ( centipoise )

Do you ever put a epoxy coat brushed on you 2k before you put the cloth down??

I’m running 6 tests on glass thursday. I will let ya know how it turns out… Will try and get pics

#12

I really think our air bubbles are being introduced while working it into the fabric as well. moving a flat surface (the squeegee) over the weave pattern introduces air and even using a roller doesn’t help that much - when I really squeeze it out to get a sample the resin is much more white from very small air bubbles. I let the part sit out for maybe 10 minutes to try and get as many of those small bubbles to degas straight from the surface.

I have run tests with an epoxy gel coat about my 2k (never been able to do this until I started using 2k IMC recently because epoxy would bead like crazy on my semi perm (770nc). No noticeable improvement - still got air gaps between the weave pattern.

Not sure what the mix cps is of sp115 but it’s probably very similar to what yours is. TDS only offers ind. component cps:

mix ratio is 5:2
68F, resin = 1166 cps, hardener = 173 cps
77F, resin = 723 cps, hardener = 131 cps

given that mix ratio i’m assuming it’s somewhere around 800 at 68F which is closer to my current working conditions

#13

2 hours is quick. Degassing is not very effective unless you can pull a good vacuum. Thinned resin can produce voids under a good vacuum from solvent boil. Wetting out the laminate stack then placing it in the mould could trap air close to the mould, under the first layer. If you are dry-stacking multiple layers, then trying to wet it out with a squeegee, you would certainly be trapping air in the stack. Consoliding = rolling the wet fabric in the mold. No gel-time? Every resin has a gel-time. Can you put pleats in the bag so it can pull into the corners? With out seeing the job I don’t know the culprit, but I can see a lot of suspects. :slight_smile: Hope this helps.

#14

In that case yes I am consolidating. I could use pleats with a traditional bag but that would ruin my production times which is my main goal right now :confused: - pleats in a bag means the bagging process take around 10 minutes, right now putting down stretchlon is more like 1 minute - 30 seconds to lay the tape around the mold at my leisure before the process starts, and then less than 30 seconds to stretch the bag over the mold. I have a valley around my taping flange that almost acts as a self sealing system when using stretchlon.

Anyways, I think I’m going to give up on wet laying - it’s just not worth it when you consider the lack of consistency.

Infusion, here I come :slight_smile: Picking up some mti hose from German Advanced Composites.

Thanks for all the help so far though guys. I’ll be back very soon to pester yall with questions about by infusion woes

Chetan

#15

I have also been looking at mti hose… post back if it comes out nice

#16

Infusion isn’t rocket science. But as a rocket scientist (aeronautical engineer) pointed out to me recently, it is science. And the process relies on good basic skills. Wet bagging is one of those basic skills. If you want to be successful with the advanced methods, you will be doing yourself a BIG favour if you learn to wet bag successfully.