Carbon fiber vs Diolen vs Prepreg

General Composites Discussions Products Talk
#1

I was curious how much different they seem.
I see so many contructions at this site that are darker black, lighter black etc… I don’t know if responsible is the fabric used, the resin that used or both of them.

Look how extremely different look this two gas-tanks.
I think that the builders of these writing here too

http://imgur.com/JcPyJzl
http://imgur.com/jAGb7AI

http://i64.tinypic.com/4v2q91.jpg
http://i64.tinypic.com/4v2q91.jpg

Always the sun light affects the look. But these two constructions are very different.

Waiting for your photos with fabric and epoxy colour used.
Thank you.

#2

Diolen will do not give you any results even close to carbon fiber as a visual layer. Some companies use it for the inner layers because it is black.

IMHO all this products are made with carbon fiber as a visual layer, but:
can be difference in the carbon fabric type and the quality of carbon fiber used
can be difference in the mould quality
can be difference in the gloss of product
can be difference in the coatings (propably one product is painted and one no).

#3

Also, some builders dye their resins to aid as a sort of non yellowing formula.

#4

Do you mean clear coating with varnish?
Does anyone use clear coating with a little black inside for seem darker?

#5

No. I mean before infusing or doing a wet layup, put a small amount of pigmented dye in the resin beforehand. The idea is that it can’t turn yellow if the resin is black.

#6

I think the oversight here is that most translucent dyes are not UV stable either… So over time, the dye will simply disappear, and the resin will return to it’s original clarity (with yellowing, if any).

Realistically, there is only one way to prevent yellowing, and that is with a high quality clear coat that contains good UV blockers. Easier said than found…

#7

I have been testing some clear epoxy which claims to have UV protection additives. I am very curious to see if it works and prevents yellowing over time.

I didn’t know that black pigment doesn’t last without clear coat. I have been using an epoxy based black gel coat as a scratch resistant surface coat for all black parts. How long does it takes (roughly) for UV damage to erode away the black pigment enough for yellowing to be visible?

I might need to go back and clear coat some old parts this weekend…

#8

UV resistance and non-yellowing are two different things unfortunately. There are a lot of epoxies that will claim UV resistance these days, but in my experience this means that they will not crack or weaken or delaminate from UV exposure, but yellowing will still occur. Given some take much much longer, which is of course better. But I am yet to find an epoxy resin that does not yellow at all with UV exposure.

As for the black, the opaque pigments are fine. Whilst they won’t prevent UV degradation if the epoxy isn’t UV stabilised, they will still prevent yellowing as the colour is solid and will remain.

I was referring to the translucent dyes that are commonly used. So to make a carbon part look darker or give it a coloured tint, you can use a translucent dye, but most of these are not UV stable and will disappear over time. The period of which is impossible to say - as indoor decoration in a European household? Years. Outdoors all day in Australian summer? 2 weeks.

#9

The resin I am testing is claims specifically to prevent yellowing. We’ll see. Maybe they delay it just long enough to prevent anyone returning it.

I have another resin which also claims to incorporate UV protection and prevent yellowing with cf parts but it has a faint blue tint. You can’t see the blue when it has cured on cf but I wondered if they just added translucent blue pigment to make yellowing less apparent.