Infusion-finishing-gelcoat-clearcoat

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#1

Hello guys, i recently signed up here hoping to find some answers reading the topics but i now i have to ask you, hope someone will be willing to help with an advice based on experience.

First, to introduce my work a bit further… I am from Serbia and work with composites for 4 years now, you can have a look at my products here:
http://www.gonzaracing.com/forum/viewtopic.php?t=10366&start=0
http://www.facebook.com/pages/DESIGNPERFORMANCE-carbon-composites/107646032591560
These pages are in Serbian, but if you look at the photos you can see what kind of production it is.

-The problem i confronted came with a request of my customer for mat finish part with carbon appearance.

First i made a bonnet as i normally do:
0.3mm thick gelcoat (NORPOL NGA102S - polyester gelcoat from Reichhold)
Resin infused carbon laminate with DION 9102 - Infusion vinyl ester from Reichhold
after demolding it was finishet wit MaxMeyer mat lacquer

The finished product looked perfect indoor, but in the sun it has Bluish-Violet apperance-shine under certain angles.

Then i ordered other type of gelcoat, which Reichold claims is the clearest available (NGA116S) and got the similar result just less Violet. Note that these gelcoats are UV-stable, and really are (have couple of bonnets made from this standing in the sun for almost three years now.)

-After that failure i started making little A5 size flat samples and from that study i made a few conclusions.

-Mat lacquer it self is not a cause - some other parts that my client had and which were ordered from Seibon, had the same treatment and do not have Violet shine but they are slightly yellow as they werw probably made of resin which is not UV resistant.
-Samples infused with epoxy, and polyurethane instead of gelcoat did not show Violet shine. Than i added Aerosil to polyurethane (aerosil is standard ingredient of polyester gelcoats) in order to get better spray on properties (pinhole or fisheye formation and avoid dripping on vertical parts of the molds when applying thicker coat.) and found out that PolyUrethane Clear with aerosil does give a slightly bluish appearance. (Polyurethane was PPG Delfleet)

NOW i want to solve this once and for all, so i will be running another series of samples, and hope that someone could give an advice or suggest what else should i try?

Note that parts have to be aesthetically perfect and stay like that for at least 3 years.
I prefer VE resin as it cures easier (room temperature), and -from my experience- has better heat resistant properties (does not become like rubber with temperature increse, tested at 80C - parts which were post cured before test) Epoxies i used so far were from R&G and ELANTAS.

I hope someone could help, forward thanks!

#2

Hello Drasko,

I use the clear In Mould Coating from HP Textiles. It is a polyurethan system that has the same UV protection than a clear coat.
As resin I use the E3000 Resin with E300 hrdener. If you need a higher TG you can use hardener E120.

Both systems work perfect.

#3

The blue/violet appearance are due to 2 sources:

-cobalt in the gelcoat
-aerosil in the gelcoat

Avoid these and you should be OK.

#4

Is there a Polyuerthane system that works with Vinyl ester? In my tests the PU coat, after infusing VE looked like it was not cured properly and the same stuff with epoxy works fine. I tried different times before lamination 8, 16, 20 and 24 h (also divided areas with and without spray adhesive 3M 77 to see will it have an affect to the surface)

Another question is: what mold release do you use with PU? Because PU itself is forming many pinholes when sprayed to a mold. I tried with Oscars M800 and AXEL PasteWiz and one which had the PVA on top. All seem to do almost the same. That`s what led me to adding aerosil and finding out it has something to do with bluishnes…

I will have a look on PU clears for molds, which are available in EU. Any idea on that?

#5

I am thinking Duratec Cleat Coat could be a good solution for you.

#6

The HP IMC should work with VE.

#7

When you shot you the PU into the mold the first coat must go on in a very light mist/fog. I do this by by just barely opening the product release stop on the gun. You then need to let this fog coat set before shooting a full coverage coat. If you shoot it heavy with the mist coat you will get pinholes/fisheyes.

#8

I will have it by the end of the next week so it will be in the test group.
I wonder what they use to make it thixotrop… But i may find out as i will visit them in Germany next week.

Any other suggestions? Even if not sure it will work, bring it on, is always worth trying (i make more than 50 samples so a few more can`t hurt and data i get may be useful for other things than just “bluishnes” :mad2:)

#9

I know, i have even tried with different wait times before second coat and different speed hardeners and thinners but did not find much improvement. But it is not a product made for in mold use it is just normal polyurethane finish from PPG. addition of aerosil easily solved the problem but brought back the bluishnes. NOW i will investigate a bit more on PU spray and viscosity properties and try more combinations of mold release agents to see if a conventional PU clearcoat can be used or modified and used in this purpose. But i hope that HP IMC will be a solution - their scientists probably have done this work already.

#10

Drasko, I use Freecote 700 and spray PPG polyurethane as Wyowindworks described. I find (out of fear) if I shoot several mist coats each increasing slightly in amount that my final coat goes on without pin holes or any problems. It sure has saved me hours of finish work. Also I’m using Adtech 820 epoxy.

#11

What hardener do you use with your polyurethane (HS,MS?) and how long do you wait in between coats? How much thinner do you put in? Technician from PPG here recommends mixing ratio: 2:1:0,5 (0,3)

#12

I use PPG Concept 2002 with DT885 reducer and DCX61 hardener. I mix with a 4/1/1 ratio. I usually wait 15 minutes between coats.

#13

By data sheets, it seems to be a quicker curing system than Delfleet F390 i use… So i will get DCU2002 as well.

Any experience in a combination with VE resin?

#14

No VE experience but I bet Wyowindworks has. That dude is pretty knowledgable with composites.

#15

Sorry, I have very limited experience with VE resin. I use epoxy for most of my stuff.

I use a lot of PPG Deltron DC3000. I kick-off the first couple of mist coats with an IR lamp or put smaller molds in a curing oven for 15 minutes. This causes the first coats to set-up much faster. I’ve been wanting to try DC2000 which is a super fast drying clear-coat. This would speed up the process even more. Unfortunately, I’ve got a bunch of DC3000 to finish up first.

#16

I shot a few more samples today with Delfleet PU.

-Spraying technique was: Mist coat-10min-wet coat-10min-wet coat - for all samples (probably should wait more and have more mist coats but i wanted to force fisheye formation to see if there is any difference between ones with additives and what difference do waxes make)

-Fisheye preventer - additive really makes a lot of improvement! (1.5% added to prepared lac volume)

-Spraying without thinner helps

-Oscars M800 proved to be slightly better than PasteWiz and booth are better than waxed surface with PVA.

-tiny amounts of aerosil absolutely solve the problem even when you spray a thick coat straight on, so now i will try to find what is the least amount needed…

-Samples with the same PU will be infused with epoxy and VE so we will see what happens…

#17

Wyowindworks, I tryed the DC2000 and it did not adhere to the laminate very well at all. Sure like the quick curing time of the stuff though. I went to the 2002 and was very happy with results.

#18

HP-IMC is here, will have results in the following week :slight_smile:

#19

It is the best system I have used, never had problems.

#20

First impressions which concern spray on properties are good… almost none fisheyes in just one thick coat. Totally different from ordinary PU lack. I am looking forward to see how it does with VE and compare that to epoxy.