Hi I tried to polish a epoxy gel coat, sanded with 500, 1000, 1500, 2000 and then with paste and polish. Gel coat is always matt. With the same work, another poliester gel coat is glossy.
Someone has the same problem?
There are gel coat suitable for polishing and others do not?
Your experience is pretty much the same as my experience. If you are planning on needing to polish your mold then I would recommend a VE or PE based gel-coat rather than an epoxy surface coat. I use epoxy surface coats for nearly everything but I perfect my plug and use low shrink resins so I don’t have to polish the mold.
ok, thanks for the advice. I don’t usually polish molds with a gloss surface, I wanted to try with a epoxy mold but without success. The others mold are wit PE gel coat, and it works. I have another hybrid gel coat, it works with PE, VE and epoxy, but it’s transparent so it’s hard to understand if it can be polish or no.
An VE gel coat,usually works also with epoxy and PE resins?
Typically.
There are many EP surface coats that can be shined to a high gloss, what brand is yours? PE will get the highest gloss, then VE, EP last
fiber filled stuff will never polish up…
ok thanks Herman, at the sight it look like the others gel coats I have. I have not considered that it’s fiber filled
And in general a polyester polishes up much easier indeed. If you are after high-gloss tools which are not too critical in temperature than I can suggest Nord Composites RM2000 (up to 70 degrees oven temperature) or RM3000 (up to 100 degrees oven temperature).
If you want higher temperatures, use a special epoxy, or some vinylesters which can do the job.
ok…until now my molds hasn’t high-gloss finish, now I’m looking to get it.
I have always used PE gel coat with PE resin, I’m now using this EP gel coat or T30 gel coat with epoxy resin (EPR04434 with ebalta OH 82, and EPR 320+EPH160 with ET30).
I buy also a VE resin, but the shop hasn’t VE gel coat…I don’t know if my PE gel work with VE resin.
I’m trying with a carbon heater mold for infusion, temperature at about 80°C, so I need a gel coat for this temperature. I test T30 and it hasn’t problem, but it’s transparent, so it’s difficult to polish
T30 gelcoat is not recommended for moulds or heat. The only advantage is that it bonds with epoxy. The rest of the properties is below par.
EPR04434 is an utterly expensive epoxy resin, and I doubt that you are using its full potential (Tg 195 degrees). If you like to use Momentive, for 80 degree moulds I can recommend for instance L20 resin with EPH0161 curing agent (Tg 135 degrees after 120 degree cure. This has plenty of safety built in, and is much cheaper.
PE gelcoat works with VE, no problem. If you need it I have a VE gelcoat (very high gloss) specifically for moulds, with a Tg of 135 degrees. Make sure your PE gelcoat has a Tg of at least 100 degrees, if working with 80 degrees cure temperatures.
I agree with you, 04434 is very espensive and I’m not using its full potential, but it’s the only resin that shop sell me for high temperature.
In your opinion, it’s better L20 +EPH161 or EPR320+EPH161? I found the same TG for these resins, 97°C after 120°C cure.
I don’t know the exact TG of my PE gel coat…with resin infusion I have had some problems, but with PE resin and put in the oven immediately after infusion, with oven @ 80°C…so the exotermic reaction was certainly over 100°C. In this case then I have the fabric print in the gel coat mold surface.