IMC "Epoxy or ?"

General Composites Discussions Composites Talk
#1

Hello. I know this may be an aggressive first post but bare with me. I’m not new to this forum and have been around quiet awhile. I’ve read through a number of threads about IMC but nobody actually helped to much on the process if you don’t want to use automotive clear. Here’s my issue.

I’m trying to use a IMC because the part I’m making has a kevlar surface. It’s a multipiece mold as well. Typically I do carbon fiber surfaces and I use 6k fabric, and tack the layers with spray glue. This isn’t an issue because I wet sand after demolding and post curing so I sand slightly into the weave, but not to much and never enough to hit the second layer of carbon since I use 6k. After the clear my part turns out great with no traces of super77.

Now my issue is that I’m using kevlar for the first time which I don’t think I can sand, even slightly because it will fray? I typically use 400 grit sandpaper on carbon and then clear without issues. I’m afraid to use it on kevlar because it will fray and ruin my part.

Now I know some people suggest gel coat, and let that tack to use the first layer, but I thought maybe I could use epoxy? I use Adtech 820 which is UV stable and I thought about maybe spraying that on my surface with a hvlp gun, letting it tack and use that as my adhesive for the first layer.

I wouldn’t be clear coating these parts afterwards, but I would be wet sanding and buffing since my molds not perfect. It is pretty close to perfect but some of the seams are sloppy and I’ll need to knock a MM down or so.

Any advice on what to do or input would be greatly appreciated. I’m trying to not use super77 and I need some type of tacking agent in my first coat. I know DDcompound has a nice IMC but it’s just to expensive for me…

#2

I use an automotive 2k polyurethane for an in the mold coating. I mist it on for a few coats letting it dry between coats and then a final full coat. Works great.

#3

Hey man. Yeah I’m just afraid that some of my imperfections on the mold surface will be issues and I’ll need to take down more thickness than I put on clear. If you know what I mean.

Do you use the clear as your tack first layer?

I did an IMC once with clear, but I let it dry completely. It was a few years ago and I had bridging issues too and I think I used spray glue too which it didn’t turn out well.

#4

If you are using an IMC, you can use any spray adhesive you like behind it, it will be invisible.

You can use your infusion resin as an IMC, it works fine. It can be difficult to do successfully though, especially if you are using something like Frekote as a release agent, the resin isn’t designed an IMC and so can be quite prone to issues like fisheyes and sagging. Give it a go, see what you think, if you can get it to work then it will solve your dilemma.

Otherwise, investing in a good quality IMC is a good idea. They are expensive, but generally not too much more expensive than a 2k polyurethane, and at least you will know you’ve got something made for the job. Waste a litre of 2k clear or infusion resin trying to use it in mould, and all of a sudden the IMC would have been cheaper.

#5

What other IMC’s are there? You can PM me too if you’d like.

You’re probably correct with resin dripping and such with spraying epoxy.

I’m still very very hesitant to use any type if spray hour under the IMC because I use epoxy and that doesn’t break down glue.

#6

You need to use the right spray adheasive like aerofix if your worried about the glue not breaking down.

As for IMC, you can use just about what ever you want. I have used pressure pack clears before and had no dramas, just spray as many layers as you want to build a desiered thickness, then use the aerofix to tack the first layer down. another option if you want a surface that you can sand down and think you require thickness then i would be laying a few coats of resin into the mould first to build up the thickness you want (i dont know how bad your mould is).

#7

As I mentioned earlier, if you are using an IMC then it doesn’t matter what spray adhesive you use. You can use hair spray if you like, it will still be invisible. If you are building structural part then you might want to consider the contamination effects that any spray adhesives might have, but on cosmetic parts just use what you have available. I made all the parts you can see in this photo (except the ‘Harrop’ one) using an IMC and spray adhesive:

On the subject of using regular coatings as in mould coatings, this is something that has interested me but I have my doubts about it working. Logic tells me that when you spray any substrate with a coating, be it 2k or acrylic or enamel or anything, then you need to prep the substrate surface first for proper mechanical adhesion. Same goes for laminating, if you want a good bond then you need to key the surface so that the epoxy/poly/vinyl will adhere. But in mould, any attempt to scuff the surface of the coating properly would likely result in delamination from the mould surface. And if you left the surface unprepared as you do with a proper IMC, then you might pull a part that looks perfect at first, but later (days/months/years, who knows) you could end up with the topcoat delaminating and blistering off due to poor adhesion.

It is definitely something that I have given thought to, as the ability to spray replacement vehicle panels with colour matched paints in mould is greatly appealing.

#8

The IMC from German Avvanced Composites provides a chemical bond to the following epoxy layup so there is no preparation necessary. In terms of holding the first carbon fiber layer in place I most often use the tacky surface of the IMC approximately 15min. after spraying the last layer. That works pretty well.

#9

Yeh that’s why I say stick to using a proper IMC, because you know they are chemically formulated to do the job. When you start using products that weren’t intended for that purpose, you can’t really guarantee that it is going to do the job properly.

#10

If you put a thin layer of glass as your first layer before the kevlar then you wont have to worry about sanding through the kevlar and the glass will be clear.

#11

I’ve actually done a test piece awhile ago with fiberglass veil. I infused like normal. It was pretty clear but at angles the light bounces off the veil so you could see it.

#12

Wanted to bring this back up as my questions are what IMC are you guys using here in the states? What mould release systems are you using it on top of?

#13

I tried for the first time yesterday the IMC from German Advanced Composites (bought from HP-textiles as i live in Europe). Very happy with the results!!!
i do have some questionsif anyone can help…

  • datasheet doesn´t refer to how much time you must wait between layers. How long do i have to wait between layers?
  • datasheet also mentions to cure for 24h before infusing on top…but i have seen people saying that they lay the frabri when the IMC is still tacky??
  • last, i plan on doing 3 layers. Small mist, heavier coat next and full as last. Can i mix the IMC in one shot or it will cure on the spray gun?
    Following the datashhet it´s too much time wasted. I do have an oven but it says 6 hours to cure at 60degress.
    The ideal would be, mix all in one shot, spray the three layers, go to oven for an hour or so and then layup, infuse and to the oven again for the 6hours (as recommended in the resin system i use. Would this be achievable?

Thanks in advance and sorry to steal the topic

#14

That’s like I do it. Mix it once, spray three layers and put it for a hour in the oven and then you can infuse.
I don’t use it when it is tacky, it works but I had that it became milky

#15

But how long do you wait between layers? IMC won´t cure in the gun?
I usually use spray tack from Airtech so i prefer like this. I had my share of problems with milky parts from previous gel coats that i tried

#16

I’ve been using duratec sunshield clear topcoat I think it’s called. I spray with a 2.0 tip hvlp gun. For when it kicks depends on how hardener you put in but I catalyze at around 1-1.5

As for the coating before hand I use frekote 770nc then a few coats of dolphin wax so things don’t bead up when spraying. It seems to work pretty well.

#17

There is solvent in the IMC, as long as you keep it in the gun it will not be a problem for a few hours. The manufactorer HP Textiles says it is not good because it starts to react, but we have not realized any negative properties.

#18

what kind of part are you making?

#19

thanks DDCompound.
I did another try today and love it. Really easy to apply. I´m using a 1.5mm nozzle gun and it gets very smooth cover of the mould

#20

Anyone know what´s the maximum time you can wait to laminate after you apply the IMC? will it still react after some days without infusing?