First infusion just around the corner...

General Composites Discussions Composites Talk
#21

Thanks for all the help, riff!

#22

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https://www.airtechintl.com/htm/defaultIE.htm

Or register here for a wide variety of products from them.
https://www.airtechintl.com/htm/defaultIE.htm

#23

Thanks, Rotorage! I’ll take a look at those links.

#24

I pulled the layup from the last infusion and it looks great. No bubbles or voids anywhere. One thing that I found interesting is that even letting the resin cure under heat lamps for 36 hours, the first layer of fiber glass still printed through. It doesn’t look bad, but you can see it if you look close.

Here ar a couple of pics.

I received a couple samples of resins today. A big thank you goes out to the guys at PTM&W and Resin Tech.

Here are the samples just out of the box.

I am just about to set up an infusion on a mold that creates a left and right side at the same time, and I wanted to test out a setup with the new resin before I got to work on the actual mold.

I cut and layed 5 layers of 2x2 8oz twill on the glass. The peelply continues 1.5" past the stack, and I left the mesh 2.5" short of the vacuum lines making a nice resin brake. The middle line is for feed, with the outer lines for vacuum. I used .5" spiral, but 1/4" PE tubbing because it is so much easier to work with.

I connected the 1/4" vacuum lines with the resin catch pot line like so.

This is the PTM&W 2712 infusion resin, and then resin with hardner. It does have an amber color to it, but I’m sure you wouldn’t be able to tell on carbon at all.
Edit: I was just back up to the shop a few minutes ago and the resin left in the cup is clearing up as it cures. It looks like a lot of that amber color goes away as the cure progresses.

This resin also degasses much better than the US Composites 635 stuff does. It doesn’t foam up crazy. The bubbles just come up nicely to the top and pop. BTW, I didn’t have any bubbles during infusion.

Here is the package after infusion.

And a little video.
[ame=“http://www.youtube.com/watch?v=tZ4ZGTF1ISE”]Resin Infusion Test Number Two - YouTube[/ame]

#25

I pulled the FG coupons from the latest layup. They came out mostly OK, but there are some voids.

If anyone has any ideas on why this might have happened, please let me know. The video of this infusion is the one in the post above.

The infusion was composed of two stacks of 5 plys of 2x2 twill 8 oz e glass.

Peelply covered both stacks, and the resin inlet, and vacuum lines touched the peelply.

The infusion mesh was cut short to allow for a resin brake.

Infusion took 14 minutes.

-Infused with PTMW’s 2712 infusion resin. This is my first time using this resin.
-resin degassed, stacks compacted at 29.5 on my cheap vac gauge
-infused at 25"
-package left at 25" until cured over night
-shop temp and humity at inusion was 75F, 46RH
-mold temp at infusion was 88F
-resin temp at infusion was 93F

Also, I have used my new Robinair 15600 for about three hours in total now. Today I noticed that the oil has gotten a little milky. Does anyone know why this may have happened, and if it requires immediate attention?

My vacuum pumps are currently set up like so. The Robinair is connected to my vacuum press through a T before the pressure tanks. I have created a manifold of sorts to isolate the Robinair, and to vent to atmosphere.

Usually I’ll use to piston pump to remove the air from the bag. Then the Robinair comes online to debulk, remove moisture from the stack, and degas the resin. Usually I have used the Robinair while the acutal infusion has taken place. After infusion, I isolate the Robinair, and let the piston pump take over if the pressure drops past 25". This way I dont’ have a pump running all the time, and a little reduced pressure is good after infusing, right?

I think that I’m getting the hang of this stuff, but all of your help really makes the difference. Thanks, everyone!

#26

Simplify your life:D
Infusing at 25" in Hg is too less vacuum (depending on where you are located). You should have a absolute vac level of less 0.59 inHg (<20mbar) for infusion. Measure absolute, not relative.
The low vac level in combination with the spiral hose crates the pinholes and voids. Reducing the vac level after infusion helps to get less voids, but will not eleminate them.
I am also sure that the valves you used in your pump setup are not tight. For infusion a 100% tight system is very important.

#27

Why infuse at 25 inches…? if you dont have absolute vacuum in the bag, you are still leaving air, moisture and god knows what else in the layup.

I pull as close to 100% vacuum as my pump can generate. Why? The moisture at typical room temp will boil off at about 25 mbar or 29 inches. If you didnt reach this level, you still had moisture in your layup. Whilst the moisture is boiling off, you may observe the oil in your pump go milky. Once all the moisture is boiled off, you will see the oil go clear again and you will reach a higher vacuum (if you pump allows). Proceed with infusion after all the moisture is gone.

I infuse whilst maintaining as close to absolute vacuum as possible. Dont reduce the vacuum until after infusion.

http://www.jbind.com/pdf/Cross-Reference-of-Boiling-Temps.pdf

Any remaining air in your layup will end up accumulating in areas of high permeability. ie. places that would be resin rich if no air is present. If you look at your photo, you will notice the voids are located between the fibre tows, the tows themselves are wetted through, so the air has accumulated in the small places of high permeability between the tows. This is air inclusions from air remaining in your stack or air introduced during the infusion (leaks or dissolved gasses in your resin). If you dont introduce any air in the resin ( i know you degassed, but you never get it all out), and dont leak any air, and dont have any air in there before you begin, you cannot have any voids.

#28

And after infusion turn off the heat lamps until it gels ( heat gain after infusion could expand any air or start to offgas because of the heat.)

#29

^ That’s a prety interesting comment Cheekybrad :wink:

#30

With heat the resin gets a lower viscosity. So it is easier to travel by the brake zone in the spiral, the open vacuum. The enclosed air wants to expand because the vacuum in the spiral can still pull resin. A bigger brake zone minimizes the brake zone because it is not so easy for the resin to travel away.
Thats one pro of the MTI hose. The resin can not travel away so that airbubbles are minimized by full ambient pressure. Than you don’t need a brake zone and can cure by heat without any problems or becomming voids or pinholes.
Type “MTI how it works” in youtube, there is a animation wich explais what happens with spiral.

#31

You need to change the oil in the pump after so many hours of use. This will keep it running for years to come.

#32

About the oil. I changed the oil yesterday. It came out very milky.

Last night, I did another infusion and now the brand new oil is milky again. The pump only ran for maybe 3 hours total, but I would say probably less. What could be causing this?

The pump isn’t pulling a bunch of air. I have a piston pump that pulls the bag down, and takes over after the infusion is finished, so the Robinair is only consolidating the stack, running an hour or so to pull moisture from the dry stack, degassing the resin, and pulling during the infusion.

Now that I think about it. The oil turned milky about half way through my work yesterday, so not even 3 hours into a new oil change.

Please help!

Thanks, everyone!

#33

Keep it running? Can you touch the pump? You should not be able to touch the pump housing (hot!). What is the humidity in your area? When high, a considerable amount of moisture can be trapped in your materials, and probably you are still pulling moisture from the stack.

Your picture of the oil does not impress me. I have seen much more milky oils…

#34

I use a 2 stage rotary vane pump and it goes like this;

You start with good new oil, looks great in the sight glass,
When you pull the bag down, the vacuum builds and you will see vapour ejected from the pump exhaust,
you will continue to see vapour for a while and you will notice that your oil has gone milky,
you can still hear vapour bubbling through the oil as the moisture boils off,
after maybe an hour or so (depending on a few things) you notice the bubbling of the oil has stopped, no vapour passes the pump (otherwise you have leaks or there is still moisture in the layup), the oil goes clear in the sight glass again…

now your ready to mix your resin and begin infusion…

#35

Thanks for all the help!