Thinning resin for wetting carbon

[Mr DIY]

Does anybody thin their resin when wetting out carbon tows. From what I have heard, resin can be thinned with suitable 'thinners'. Anybody tried this, and if so, how are the properties of the resin affected.

Brian

[davidfee]

I would not suggest thinning resin to make it wet out fabric or tows more easily. It can weaken the finished part. It's better to just heat the epoxy (are you using epoxy?) to make it flow better. Better still is to use a lower viscosity resin to begin with.

-David

[Mr DIY]

Thanx for quick reply David. :)

I have bought the lowest viscosity resin that is suitable for moulding (known in my part of the world as SP106) , but a friend came up with the idea of thinning it more. Was not sure about this .. so posted the idea. To me it does not sound a good idea, but you never know.

PS: At long last we have made it out of the trial area :cool:

[davidfee]

PS: At long last we have made it out of the trial area :cool:

Yes, it's a good day. :)

If you find your low viscosity resin is still giving you trouble, just warm it up with a hair-drier or heatgun. This will accelerate the cure also, so you may need a slower hardener in some cases. I don't think you should have any problems though.

If you use alcohol, for example, to thin the resin it might not evaporate before the epoxy cures. It will then be trapped in the epoxy for some time and the resin will not cross-link completely.

If you're working in a mold, any solvent you use may also dissolve your mold release (not good).

have fun,
-David

[Mr DIY]

If you're working in a mold, any solvent you use may also dissolve your mold release (not good).

Oh my goodness ... YES .. that could spell a big problem.

Even the Extra slow cure was going off to quickly for me. I have done the warming trick .. but got to work fast!! :)

[foofighter]

You really dont want to start diluting the resin. Even at 10% volume levels the final result will be 'plasticized' to some extent.

Which hardener do you have with the SP106? The extra slow hardener may give more open time but the mix viscosity is notably higher than with the slow hardener. (about 25% higher)

Either way, really low viscosity wet layup resins such as Araldite 3600LC would be really lower by comparison.

Careful with applying heat from non-thermostatically controlled equipment, exothermic reaction can happen real fast (and believe me, you dont want to go there!)

[davidfee]

How viscous is this resin? I've never had problems with the laminating resins I've used. Recently I've switched to MGS L285 (a German epoxy) which flows almost like water... it's great.

[Mr DIY]

How viscous is this resin?

http://www.z-clad.com/pdf_files/SP106.pdf

At 25 degrees C = 815. Numbers mean little to me though. What would the viscosity of water be in comparison?

Brian

[foofighter]

The important numbers are the 'mix viscosity' as that it what you are working with. ie 862cP (slow) and 1149cP (extra slow)

The 3600 mix would be around 250 - 300 cP at the same temperature.

Water has a viscosity of 1 cP at room temperature.

[Mr DIY]

A quick search show numbers of around 1000 at 20 dgC for water.

http://www.engineeringtoolbox.com/24_596.html

Numbers drop as viscosity goes up. Strange .. the resin does not feel 'thinner' than water. Must have another feel when I mix some resin this weekend. :)

[Mr DIY]

Ah .. we posted same time foofighter.

Had another look and what you say makes sense. All fits togethor now. Thanx

Brian

[shoe]

How viscous is this resin? I've never had problems with the laminating resins I've used. Recently I've switched to MGS L285 (a German epoxy) which flows almost like water... it's great.

I second this, I use MGS and never have a problem with it not being thin enough. Besides that I love the lack of odor...mmmm and the pretty color.....

[davidfee]

Gotta love that crystal-blue color of the MGS! The mixed viscosity for L285/H285 is published as 300-500cp.

Anyway, what's the project, and what method(s) are you using for wetting out your reinforcements?

-David

[Mr DIY]

Anyway, what's the project, and what method(s) are you using for wetting out your reinforcements?

Not sure if the question is directed at me or shoe, but never the less, within the next few weeks, I will be starting to make some moulded wings for a 3+ meter F3B hybrid. Trying to find out what works best for wetting out the carbon tows.

My last project saw me twisting the tows to break down the bonding agent that hold the fibers together that is used to create a neat tow that winds nicely onto a bobbin. This process took a long time … and I have since learnt that I was probably doing damage to the carbon when doing this. Anyway, those prefabricated spars I made, have not let me down and are still flying in my 4m plane.

From what I have seen, some people just cut the carbon, lay em down on some surface and apply resin with a sponge. I had my doubts about the resin penetrating the ‘bonding agent’ properly, but this seem not to be of concern?

Brian

[davidfee]

Usually the fibers will wet-out just fine, especially if you use vacuum. I assume you will be, if it's a molded wing. Also, I have seen many machines for wetting out tow. Some are very simple, made just from a polyethylene bottle with a squirt-bottle tip. Others are more "fancy," like this one:
http://www.delago.com/ariane/images/tn1.jpg

See more from Team Ariane (dated material, but still useful):
http://www.delago.com/ariane/EHome.htm

good luck,
-David

[davidfee]

Yes Brian, my question was directed at you. Sorry I wasn't more clear. :)

-David

[Mr DIY]

That plastic cup.... What is its purpose considering the resin would be in the blue container?

[macr]

I would guess that the plastic cup has the resin and the blue thing squeegees the excess out.

[davidfee]

I'm not sure about the plastic cup... I think it does hold the resin.

Here's another one, this time from M. Koch:

[Mr DIY]

At first I thought the plastic cup was holding the resin, but with the tow coming out the bottom, what is to keep the resin spilling out.

The above photo is interesting. What a waste of an expensive heatsink .. or wait .. is that a power cable showing at the back? edit (oops ... only got part of the photo) Nope ... for a moment I thought this baby was being warmed.

Brian

[macr]

At first I thought the plastic cup was holding the resin, but with the tow coming out the bottom, what is to keep the resin spilling out.
Brian
Sponge, or maybe a rubber grommet, like a camel back bite valve.

[Mr DIY]

Sponge, or maybe a rubber grommet, like a camel back bite valve.

Yep ... those ideas ought to work. Like the second photo though. Will probably make up a hybrid from the two ideas.

This thread has turned out pretty usefull. Thanx Guys :)