Okay so I just completed my first mold and everything looked perfect...from the outside. As I pulled the part from the mold I noticed the part had been completely alligatored through the OEM paint and into the abs plastic part itself.

What caused this?! I didnt use too much MEKP I actually used a little less than I was supposed to. I waxed and PVA'd several times while useing the proper precautions of waiting to dry in between coats. The only thing I didnt use that could have been a causing factor is a hi-temp wax. I actually left it at home so I used Honeycomb wax or HoneyBee wax..something like that. It comes in a yellow container.

I will be producing more molds from plastic parts and dont want this to happen again.

Thanks for the help!

Hi,

Can you give me a little more information about what mould making materials you're using? - Is it our Uni-Mould Vinylester Tooling Gelcoat or something different?

Using wax that's not Mould Release Wax certainly sounds like it could be problematic.

Regarding using too little MEKP, actually, this could cause a problem not reduce it. It's the styrene in the gelcoat that's attacked your paint. The longer the gelcoat sits on the paint, uncured, the more time it has to attack the paint. If you can the gelcoat up at 2 or 3% then it will cure much quicker meaning it has less time, in its uncured state, when it can attack the paint.

I hope this helps.

Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

I had the same problem with plastics that where not clear coated and I guess it was due to exotherm of Gelcoat or Resin while molding.

Hi,

It happened exactly the same to me, when i´ve done the mould of my bonnet, the paint went damage.

I have another bonnet mould to do and i´m affraid that happens the same.

With the Uni-Mould Vinylester Tooling Gelcoat it dosen´t happen?

Pedro

It shouldn't happen. Use Chemical Release Agent and Mould Release Wax (several coats of chemical release agent followed by several coats of mould release wax). Ensure that you have a good level of catalyst in the tooling gelcoat (2%) and that it's not too cool/cold where you're working at it should be fine. As you can see from our video the bonnet we took a mould from was undamaged. If in doubt, do a test on the inside first.

--Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales