Another PVA question, but a new one ;-).

General Composites Discussions Composites Talk
#1

So my new process of making high quality full carbon parts, (for strength and appeal) requires me to put the fabric into the mold with out coating the mold with a clear top first.

I’ve been waxing, then just wiping PVA with a microfiber towel and then putting the fabric in with super77. It works pretty well, but sometimes I get vinyl ester residue stuck onto the mold.

I’d like to coat all the molds nicely with PVA and then lay the carbon fiber in, but since I need the super77 to keep the fabric down. When I go to press the fabric into the corners or when the fabric shifts very slightly it tears the PVA. When I go to infuse resin leaks through those tears and traps the PVA into the part, and or fills the corners of the molds with resin I then have to really work to pluck out.

Is there a way around this? If I spray several mist coats and then a flow coat of PVA do you think that will help? I’m using reXco Partal coverall film. The purple stuff. I’ve used the Partal green as well. Is there a PVA that is stronger as far as tearing goes?

#2

any reason you want to use pva? using a semi-permanent release is the way to go, solves all problems quickly and reliably.

#3

Hojo- Does that mean using a wax?

#4

^ Lol, x2. I’ve been using a carnuba paste wax by meguiers. Not made for composites, but its been working. I’m scared some of my molds might stick. I used a heavily seasoned mold last week and destroyed it not using PVA. However, the mold had many super detailed sections. It had letters and markings in it for a car brand so maybe in special cases I’ll need PVA?

#5

Semi-permanent releases such as Frekote, and several other brands are liquid chemicals that chemically bond to the mold surface. They work much better and are more reliable than wax in my opinion. And you get a perfect finish and no added steps like using PVA. Also depending on the application and the release agent choosen you get several pulls before reapplying. In my opinion its the only way to go for production.

#6

hojo 100% right I use Chemd Trend and #88 wax and I can get about 20 pulls from my molds before I have to add release to them again.

http://www.freemansupply.com/datasheets/15sealer.pdf

http://www.freemansupply.com/datasheets/Chemlease/ChemleaseOneFS.pdf

#7

Where can I purchase any of the above? Any distributors in the US?

#8

I get mine from CompositeOne.

http://www.compositesone.com/

#9

Are you using wax in addition to the semi-permanent release?

#10

Yes I use wax because the release will leave lite streaks once cured, so once you put a coat of wax and remove the streaks are gone.

#11

Northern Composites(before Northern Fiberglass)sells Frekote, www.nfgssales.com

#12

I use super77 to adhere the layers down nicely. If I use super77 will it hold after spraying with frekote? Can anybody tell me the instructions to apply?

#13

you can use spray adhesive on frekote. basic instructions are you take a small rag, preferably scotts shop towel, wet it out lightly, ring it out so theres not too much in the rag and wipe across the mold surface evenly. First time doing a mold you usually seal it twice with a sealer, then apply between 2-6 coats of release agent depending on the brand and application. As always read the manufacturers instructions as the will be specific to the type you are using. Usually after first pull you apply one more coat then you can do multiple pulls depending on the application. Well worth the investment, PVA is not practical in real world manufacturing.

#14

I guess you are right on that. I spent half the day adding coats of PVA to make a radio bezel for a Diablo… If I didnt have to use PVA I could have made two in the time it takes to make one with PVA.

Has anybody had experience with the Frekote in a aerosol can? Or should I just wipe it on? A quick look at some sites and I saw there were many types of Frekote? Am I wrong? What should be recommended with polyester and vinylester resins. No gel coat, but straight to carbon fiber. I sand all parts after demolding and clear coat. My parts are all clear coated carbon fiber.