plug surface

i am in the process of making a plug for a fiberglass cooler. is it absolutely necessary to use duratec on the surface or can i get away with using polyester resin or gelcoat on the surface. if not what would be the next best thing for the surface of the plug?

also if i only plan to pull about 5 coolers from the plug can regular gelcoat do the job for the mold surface or is should i use tooling gelcoat? i also have a high temperature(290 degrees) black epoxy that we used to use at work but discontinued use and have about 8 gallons left. could this be used?

from my understanding polyester resins do not stick to epoxy so if i used this epoxy for the mold surface and make the coolers out of polyester then once the mold is waxed well and release agent applied then in theory the coolers should pop out with little fus!

any suggestions would be greatly appreciated!

 

Considering that most moulds are faced with polyester gelcoat and produce satisfactory components,you should be able to use the gelcoat that you have.For a handful of components,ordinary gelcoat should suffice and you will need to adequately wax the surface.
Your understanding of the attraction of epoxy to polyester is not incorrect,the bond is not optimal but do not expect it to repel the material.It is not like using a PTFE insert to form a small recess.You can use an epoxy mould to produce a polyester component or vice versa if you apply a release agent.

 

i do have an understanding of the materials as i work with many different two part resins including epoxies,two part silicones and ester resins just my explanation of it may not be the best. i understand that the bond between polyester to epoxy will stick just not optimal but it will stick which is why i said it would still be waxed and pva applied to it. the teflon liner idea would be great but i doubt our supplier would make 1 custom liner for me. he would expect a bulk order like we do with our tubing.

i will just go ahead with waxed gelcoat. thanks for the suggestions

 

For just a handful of components, waxed gelcoat should do just fine. As long as the surface is smooth and the release agent (wax, etc.) is doing its job, almost any reasonably durable plug surface should survive for five or ten pulls. The expensive tooling gels (Duratec, etc.) come into their own when you are pulling 20, 50, maybe a few hundred parts and want the mould to last a while.

For a one-off where you don't need to save the plug, it's even easier- I used shellac and furniture wax once to polish a milled MDF plug, it worked very well, but the plug didn't look so great afterwards.

 

this is an mdf plug that will be going in the trash so gelcoat it is!

thanks!

 

Dura tec is easy to mix, spray and can be buffed up to a 2000 grit finish making your parts look great!,