Infusion differences with different resins.

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#1

So over the course of my career I’ve successfully infused at least 300 parts. This past week I’ve failed 12 parts in a row. The problem was that I was infusing with Hydrex 100 VE resin at 2% in temps between 55 and 65. Between 10PM and 3AM. The resin curing at a much slower rate allowed the resin to degas in the bag and show visible air bubbles in the carbon fiber panel. Before I never had that problem because I would infuse between 12PM and 5PM. The ambient temp is usually 75 - 90 here in a normal florida day.

So that brings me to ask.

What is so different between infusing with an epoxy or vinyl ester / poly ester?

Should I use Hydrex 100LV instead of laminating Hydrex 100?

Also, other than viscosity, after a complete infusion, would there be a negligible difference in quality or success between the two kinds, (infusion resin / laminating resin)?

#2

If laminating resin is thixotropic resin for you,then yes, there are differences.

Infusion resin is low viscosity, non thixotropic. Geltime I will keep out of the equation, it can be anything.

Laminating resin has additives added, which alter the rheology of the resin. Rheology is the behaviour of the resin at different shear speeds. At high speed (lot of energy added) the viscosity drops. At low speeds, the viscosity increases. This keeps the resin in the fiber, but is impregnatable (is that a word?)

Anyhow, when infusing with laminating resin, you get resin flow up to the point where the resin speed drops, and the viscosity increases. This causes the resin to stall.

#3

Herman is the “man”! :slight_smile:

#4

The main differences between different resin/hardener combinations in matters of handling is the viscosity and how it relies to temperature and time and other factors.
As herman said classic general purpouse blends are more thixotropic and infusion resins are usually not. Laminating resins tend to have a higher initial viscosity than infusion resins and nowadays there is an increasing number of infusion resins with a very low initial viscosity sometimes going down to 120MPaS.
With increasing temperature usually the geltime gets shorter and the fluidity gets higher. The manufacturers have diagrams with the numbers for their products, which usually depend on the hardener.
The “quality and success” of composite manufacturing depends on your goals. If a nice look is all your after, then getting out the bubbles should be enough, but usually composite parts also have to achieve structural and sometimes thermal and chemical demands. Price, Usability, physical properties: pick any two. :slight_smile:
In your case using a LV resin would speed up the wetout of the fibers and improve the evacuation of the outgassing bubbles. But bear in mind that all the bubbles have to go somewhere. Only the bubbles at the resin front dissolve in the vacuum, all the other bubbles have to get out of your part somehow. First they are flushed out by the resin flow (which brings in fresh resin with more gas) and second they follow their buoyancy and just lift. In that case it helps to have enough space in the flow mesh and additionally it can help to angle the part. Think of air bubbles below ice cover.
Best preparation would be of course to outgas the resin in advance.

#5

As far as I know… Hydrex 100 is a non-thixotropic resin so there shouldn’t be issues with the resin thickening before gel stage. However they make a low viscosity version of the Hydrex 100. And I’m sure its not for no reason haha.

#6

Knowing that Hydrex 100 has a 15 min gel time, would it help if I degas the resin before adding in the mekp-9? Or do I have to catalyze first then degas. I don’t think I have enough time to degas after mekp.

#7

Thixotrophy is not the same as viscosity. Viscosity always rises with time, that’s what we call gelling and hardening. Thixotrophy is how the viscosity behaves during shear stress of the liquid resin.

I’m not a user of Hydrex 100 but there are different versions with different gel times. Degassing is done with the ready mixed resin and you can do this as long as you feel like. If you now are working with 15 min gel time take a different version of the Hydrex 100 and let it boil ca. 10 min with the highest vacuum you can get. Stirring or mechanical movement during degassing helps the process. Special infusion resins often contain additives to ease degassing. Make a test if the remaining time is still enough to wetout your whole part. If you want to be void-free infusion should be at a lower vacuum (ca. 50-100 mbar), but this will also give you a little less Vf.

#8

How many in/hg would that be?

#9

50-100 mbar ≈ 1.5-3.0 in/hg

#10

So if I’m using a pressure pot how do I do that? I have an hg gauge and a valve.

That’s real low, I thought my math was wrong. Wouldn’t air rush back into my mold? I’d have a resin rich part wouldn’t I?

#11

From the top of my head I think there are also thixotropic versions of Hydrex100.

15 minutes is very fast. For infusion, I personally like to have an unpromoted version, and promote myself. A small range of tests give you a feel for catalyst and cobalt levels needed. For extra long geltimes acetyl aceton can be used. (in very small increments, 0,1% already has a big effect).
Also catalysts come in various sorts. (many distributors still need to discover that)

For the best parts:
-degass your resin after mixing. Do this at 10 mbar or preferably below.
-infuse at as low a pressure as possible
-bring the pressure up to 50 or 100 mbar after infusion, this makes voids collapse.

On rheology modifiers: typical ones used are glycerene and silica, but it is a lot of work to do right.