greetings… I have been infusing these side diffusers for a very long time but recently i am getting these white spots randomly… i took few pics and maybe someone can help.
layup is
Spray Polyester in mold gel coat (infusion grade polyester resin)
12k 19.7oz cf
20 oz woven glass
peel ply
green mesh
bag
I tried degassing the resin and it didnt help, i used to make them before without degassing and didn’t have this issues. i do have filter on my air compressor when spraying gel coat.
personally i think my gun is too old or little abused and mixing air when shooting. now this doesn’t happen everytime. i used the same gun 2 days ago and got perfect pieces and 2 days later did everything the same and have these spots …
Thank you
Adhesive…
That looks like delamination to me. What resin are you infusing with, same polyester you are using as the IMC?
What type of release agent are you using?
How long after you sprayed the gelcoat did you shoot the resin?
My first thought is that the fibers are coming through the gel coat in the light areas, like a high spot breaking through to the surface. In the right light you can usually see if there is clear on top of the fibers or if the fibers are exposed to the surface.
Looks like the Gelcoat was tacky when you placed the fibres in the mould. Then you pressed some dry fabrics with the vacuum in the gelcoat and cut the way of for the resin.
Means that are mini dry spots where the fibres hit the gelcoat.
Thats what I think.
Thank you all for your response… made few more sets and problem is still there. started using less adhesive and seems to help but still get them here and there… to answer some of your questions…
Q-That looks like delamination to me. What resin are you infusing with, same polyester you are using as the IMC?
A-we use polyester resin for infusion as well.
Q-What type of release agent are you using?
A-cure fast 1.0 semi permanent sealer/release from lilly-ram (plastilease)
Q-How long after you sprayed the gelcoat did you shoot the resin?
A- minimum of 8-10hours
Q-Looks like the Gelcoat was tacky when you placed the fibres in the mould. Then you pressed some dry fabrics with the vacuum in the gelcoat and cut the way of for the resin.
Means that are mini dry spots where the fibres hit the gelcoat.
Thats what I think.
A-the gel coat was definitely not tacky when we placed and infused and that is why we have to use some spray tack to hold the fabric in. they are so random ! yesterday i made a set which were sprayed at the same time, one mold produced perfect piece while the other mold had the spots again !’
we use 3m general porpuse spray adhesive, we started to use alot less of it and it helped, but still getting 50% of the parts with the imperfections… just ordered the [FONT=arial]Airtac 2 Temporary Spray Contact Adhesive and hope that would help… any thoughts?[/FONT]
When you spray the adhesive does it “spit” at all? If it is you will get similar inperfections to what you are having. Scraping through the gelcoat with a knife blade to the inperfections to see if it is glue if possible. It will be gooy if it is adhesive.
Doesn’t look like an adhesive issue to me, it’s too uniform. Every occurrence is in the middle of a fibre bundle, spray adhesive issues don’t show up like that. Not in my experience anyway.
I still say it looks like delamination. Whether that is due to over-application of spray adhesive is something you might consider but I doubt it personally.
I’m a little bit confused about your resins. Are you using an actual gelcoat, or are you spraying infusion grade polyester resin as your coating? I know that the chemistry differs between resins, but generally polyester does not bond well to polyester unless there is some sort of air inhibition on the open side, as there is with regular gelcoats. You mention that the coating wasn’t tacky, so that sounds like you aren’t using an air inhibited coating. That in mind, if you are using your infusion resin as a coating, I’d be questioning the bond strength between the resin and the coating.
Does the situation improve if you infuse the part while the coating is still slightly tacky?