I’m infusing panels with AOC vinyl ester infusion resin. Laminate schedule is Gel coat(20mil), 1708 vector ply, 1/2" core GPC1(that’s grooved on one side and preforations), 1708. After a few days I can see indentions in the pattern of the prefs. I tried a 1 1/2oz mat skin coat and it improved but I could still see the print. I also tried some soric TR and soric finish mat. It is better but I want perfect. Anybody got experience with barrier coats or other means of blocking print? Thanks in advance.
How long are you allowing the part to cure before demolding? Print-thru several days later is a sign that the resin is still curing. Curing it fully in the mold will help offset print-thru.
I also second what was said above. I only use epoxy but let my parts cure for 2 days in the mould with the vacuum still going, then pull and post cure, but post cure outside the mould…
It’s solved my print through issues.
Make sure you allow the skin coat to cure thoroughly before you infuse over the top. Ideally gel coat and skin in the morning and then infuse the next afternoon. You could try a 3 oz skin coat and switch to a 1700 instead of a 1708. Switching to a VE/DCPD blend or epoxy may also help.
Indeed, the amount of cure of the gelcoat and/or skin layer is critical in preventing print. This can be achieved by using different peroxides, adjust temperature, wait longer, and spray/roll/laminate thicker.
All kind of print blockers can be used (sprayable / rollable, veils, felts)
The peak temperature of the part can play a role as well. Again, another peroxide may help, with faster final cure.
And the hole diameter can be decreased. Are they 1/8" holes now? You can use 1/16"
I agree with the previous answers, I let the gelcoat cure as long as possible before infusion and demold as late as possible. Post curing is a way to speed things up and make sure that resin has fully cured.
Thanks guys, I’m gonna try to let the gel cure longer. How long is too long? I wasn’t letting it cure that long before. Also I’ll leave the part in the mold longer. Oh yea, the holes in the core are 1/16 Herman.
When not in a hurry I usually let gelcoat cure for 48 hours, spraying a mist of aceton makes tacky the gelcoat again for placing the carbon
I am surprised you can see the print of 1/16 holes, through gelcoat, skincoat 1,5 oz, and the 1700 multiaxial.
What is the exotherm of the resin?
Is the 20 mil gelcoat wet or dry?
You can also try Alpha Methyl Styrene 1% - 2%. This adds about 20 degrees to your TG and slows your gel to peak cure temp, it is not an inhibitor.
Herman, I don’t know the exotherm, haven’t checked it. The 20 mil is wet. I really believe I haven’t been curing the gel long enough. Also in the curing of the resin, I haven’t noticed an excess in heat. I ordered some Lantor finish mat and Vector Ply 1208 for my first laminates then core and then 1708. I really need to keep the weight down. I should be ready to do some more test panels by the first of next week.
You could increase the gelcoat thickness to 25 mil wet, or even 28. This should help.
I may try a panel with surfacing veil in the next few days so I’ll let you know how it turns out.
Putting space and cure in between your gelcoat surface and thickness variations in resin (i.e. through core perforations) is the aim. But eventually, that space needs some reinforcement, you don’t want to get around with 1/8" gelcoated parts!
Ensuring gelcoat cures before back up laminate is certainly necessary, you don’t want to suck the laminate through a curing gelcoat. Just make sure you don’t leave gelcoat to cure so long it pre-releases, particularly if you have a female mould.
Beyond that, you should be considering VE barrier coat, surface tissue and or skin coat before infusion.
Infusible’s suggestion of a VE/DCPD skin coat is a winner. The DCPD cracks off the cure in thin laminates with minimal shrinkage, whilst maintaining several VE qualities. Once you’ve got a Barcol up to infuse over the back-up, very unlikely to see shrinkage.
Good luck!
Putting space and cure in between your gelcoat surface and thickness variations in resin (i.e. through core perforations) is the aim. But eventually, that space needs some reinforcement, you don’t want to get around with 1/8" gelcoated parts!
Ensuring gelcoat cures before back up laminate is certainly necessary, you don’t want to suck the laminate through a curing gelcoat. Just make sure you don’t leave gelcoat to cure so long it pre-releases, particularly if you have a female mould.
Beyond that, you should be considering VE barrier coat, surface tissue and or skin coat before infusion.
Infusible’s suggestion of a VE/DCPD skin coat is a winner. The DCPD cracks off the cure in thin laminates with minimal shrinkage, whilst maintaining several VE qualities. Once you’ve got a Barcol up to infuse over the back-up, very unlikely to see shrinkage.
Good luck!