(Prime 20 LV infusion Epoxy) foaming under vacuum

Discussion in 'Materials' started by otseg, Jul 16, 2009.

  1. AndrewK
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    AndrewK Senior Member

    Otseg,
    If you do not want to change resin then you can only play with temperature and pressure to control the boiling. Since you control the resin and mold temperature looks like you need to establish what the critical pressure is and infuse just below this threshold.
    I am not clear on what is happening as you say that at constant 20 millibar the gassing is only occurring at the first feed but not at the subsequent ones.
    Then you also say that when you infused at 600 millibar (400 millibar vacuum?) there is no gassing but as you increase to full vacuum gassing begins as expected.
     
  2. otseg
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    otseg Junior Member

    We use the first feed line to fill the the next adjacent feed line completely and actually a foot beyond. The diference then is that the first feed line is empty under the bag, the subsequent feed lines are full. This helps greatly.

    If the feed lines after the first ones are not pre filled, then they foam just like the first one.

    I shot a boat a week previously in VE and had not this issue. I can't say I am an epoxy neophyte as I have been building various boats with epoxy since 1969, switched to VE, and now back to epoxy, principally for the properties, one of which is that the very high flash point of epoxy settled down a very twitchy fire marshal

    I never wanted to be the lab rat, but it seems like I need to make a series of tests varying the limits of vacuum and temperture that this particular product can be shot at. I invested a $1200 in two precision vacuum regulators to put in my system. I don't think just bleeding off the catch pot would be control enough.

    As I said before, starting with less vacuum at the initial fill and then pulling it down did not work.
     
  3. AndrewK
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    AndrewK Senior Member

    "As I said before, starting with less vacuum at the initial fill and then pulling it down did not work."
    This is what I do not understand, if the subsequent lines get filled without gassing up why would the first line once filled at lower vacuum also not remain filled ie gas free when at the same vacuum.
    The only thing I can think off is that the pressure in your subsequent lines is higher than the initial 20millibar. Have you tried connecting gauges to all lines to see what the pressure distribution is during the infusion?
     
  4. otseg
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    otseg Junior Member

    I have no idea why the first line when filled with the part at 400 to 600 millibar's would foam when the vacuum was increased. I know I don't do that any more!

    The vacuum on the rest of the part is only less from the first moment when you open the feed lines.

    I shot 5 parts today at 300 millibars. These were small parts, ie console, door and leaning post for a power cat we are putting in production. They appeared to infuse normally. I will see when we strip the bag. I wish there was some test data to be shared as to laminate properties shot at various vacuum levels. I did not vary the vacuum level on these parts as they gelled. (see lesson learned # 759 above) Its under vacuum over night. We will be doing the hulls later in the week.
     
  5. AndrewK
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    AndrewK Senior Member

    Otseg,

    "The vacuum on the rest of the part is only less from the first moment when you open the feed lines".
    If the second line is not foaming I was suggesting that the vacuum was much less then the initial 20mb abs pressure, although I would not have expected it to be. It would be good to know.
    Before I discovered that the fast hardener was my problem I experimented infusing at 400 & 200 mb abs pressure, I found the rate to be noticeably slower.
    I have not seen any comparative laminate data for infusion at various pressure.
    If resin content is approx 50%wt with no vacuum consolidation and 70%wt with 20mb then the resin content at 200mb will be somewhere around 65%wt. So the laminate properties would not be too different from what you have been getting.

    You mention that you make your own distribution line, are you willing to describe this.
    I use spiral wrap and would like to avoid the imprint it leaves if I could.
    I had thought about making my own version of omega lines out of molding silicone but have not tried yet.
    Is it worth attempting?

    Andrew
     
  6. otseg
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    otseg Junior Member

    Supplimental feed lines are quite happy to foam if not sustantially filled by the resin front.

    Wrap the feed lines in flow media and lift the body of the line off the laminate stack as you are pulling down the laminate. We did this as a method to possibly difuse the foam before it hit the laminate stack. It helps, plus it keeps the exotherm in the line off the part

    I went through a thousand feet of silicone omega and we found the vynal extrusion version to work as well. We were diligent in applying release to it after each use, it stripped fast but I had one guy who did nothing but clean and apply release to it. I don't use it any more.
     
  7. Richard Atkin
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    Richard Atkin atn_atkin@hotmail.com

    Who said boatbuilders are always looking for ways to rip off the customer? Nice to see all you guys care so much about quality.
     
  8. otseg
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    otseg Junior Member

    We did not experience any problems with these small parts. Nor did we with the hull. One variable is that the laminate was substantially single skin. Another is that the other parts we made were all cored and laid up on a temperture controlled (85 F) flat mold. Since the molds for the small parts and hull were ambient temp, perhaps the higher temp and higher vacuum for the other parts are more condusive to boiling of the epoxy components.

    [​IMG]

    [​IMG]

    [​IMG]
     
  9. wigentd
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    wigentd 3Dweaver

    foaming in epoxy infusion

    I saw your thread on boat design
    http://www.boatdesign.net/forums/ma...usion-epoxy-foaming-under-vacuum-28395-2.html

    Did you ever solve the foaming?

    We have seen similar results with sc-15 epoxy and carbon fibers recently.
    Our R&D staff ran some vacuum trials a few weeks ago indicating nucleation of gas from solution at room temp and -22-25inHg vac or so, but only in contact with fiber.

    I was particularly interested in your description of the difference between the primary inlet strip filled from supply, and the follow on strips filled through fiber from primary.
    Also, the invisible foam scar that does not bloom under the flow strip until the vacuum is raised is interesting.
    Together, these two phenomena may hint at mechanism.

    While tumble/mechanical mixing seems to the main difference, there are more differences between resin in the 1st strip and the 2nd 3rd ….

    1st strip 2nd 3rd …

    System vacuum resin supply vac
    in dry pack and at flow front vacuum pump dominates because gasses migrate to exhaust much faster than flow front advances
    ,,,,just behind flow front, resin side friction (or lack of) determines if vac state is closer bucket head or vac system setting

    fast fill strip slow fill strip
    poured over top fast wicked edge-in slow
    virgin pocket resin degassed through fiber

    dumping virgin resin (never touched extensive nucleation surfaces like fiber) quickly top down through thickness both traps air between filaments under strip, and also leaves a pocket of virgin resin under the 1st strip…
    under the fill strip the pressure is near ambient atmosphere or even positive head pressure so out gassing is suppressed only after initial fill….
    virgin resin pocket under strip with trapped/solved gasses gets bypassed by ‘leap frogging’ resin after that because following resin flows around the static pocket of virgin thanks to flow strip medias lesser resistance.
    Resin crossing fabrics between fill strips is constantly exposed to vacuum and fiber surface area at leading edge of moving flow front where gasses may nucleate on fiber surfaces and still have just a couple mm of path to escape out into dry fiber and exit to Vac pump…
    2ndary strips fill slowly edge-across from constantly degassing resin filtered through fiber rather than virgin from bucket so no trapped pocket of virgin resin means no instant or even latent foamy stripes.


    Possible corrections for process are:
    -lower vacuum levels
    -infuse beneath experimentally verified press/temp boiling point might suppress most nucleation and bubble will be smaller.
    -I think even 20% the vac will get 80% the flow rate and 80% the compaction.
    -pinch off resin inlet briefly upon filling just half the initial fill strips length and let vacuum recover there to effect resin while degass distance is only inch or so.
    -give 1 min or 2 for wicking and degassing to make the patch under the fill strip more like the rest of the fiber pack will be later.
    -reopen resin supply slowly (newly incoming resin should leapfrog around the initial wet spot like always and be degassed on the fly as front moves)
    -perhaps slowly slide the fill strip over a bit to further flush out the virgin pocket into the flow stream and fiber pack.



    i would really like to hear how things pan out
     
  10. otseg
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    otseg Junior Member

    I am working on some bids now but when I get some time to digest your response, there are some interesting points to address. Here, by the way, is a finished Compmillennia 6.7 fast cat set up for tournament fishing. 0-30 mph in 3 seconds and just tops 59 mph. The bottom picture is 42 mph with one engine off and tilted up. 3.5 mpg @ 35 mph and 3mpg @ 40 mph. Efficiency K factor works out to be 10-5 pts more than a good V bottom. The rumor in town was that Fountain Powerboats was testing a secret military boat, at least until they were passed and they saw the Zuk's on the back. :)
     

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  11. gofish34
    Joined: Jul 2009
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    gofish34 New Member

    Compmillennia 6.7 Catamaran

    Otseg graciously gave me the day off Friday so i could go fish The Big Rock Blue Marlin Tourney with a friend on his 50' Carolina Custom Sportfish - Miss Tammy. We didn't catch a winner but his mate did have a fishing license! When i got back Friday night - I hadn't had enough of the crystal coast yet so i had to go back Saturday. I'm (helping my Dad) in the process of building a 34' center console for our use - its got about 30 more to days to finish so i was able to grab the 22' Catamaran from the office to take out Saturday. I have ran many hours on the Pamlico River in this boat but we haven't gone out of Beaufort Inlet yet. Although it wasn't real snotty going out of there Saturday - it was typical for that inlet with 2-3' chop with occasional 4' roller coming in. I was totally amazed on how the boat ran and handled. To be honest i had never been in a catamaran in the ocean - it was unbelievably smooth. To be able to sit on the leaning post and drive in 3' chop @ 42 - 45 mph and not being beat to death is something you don't get to experience too often. My last boat i sold in order to build the 34' was 28' True World (Master Marine) center console with twin 225 Optimax - great boat - still miss it - but riding in 3 - 4 @ 40-45 you would get beat and be about 33 GPH - Saturday i was burning 12 GPH @ 40 - Now I have big decisions to make this fall when king fishing, with the group i normally fish with - they all fish really nice 28 - 34' center console production boats which I will have my custom that i can fish with them, but I'll be burning 25 GPH compared to 12 GPH and I'll probably be able to pass them if i take the catamaran. Oh well i still got a while to decide before cooler weather brings the big king bite.
    I have decided I'll be making more trips to Atlantic Beach and few other areas in the coming weeks - if you would like to get a test ride on the catamaran just let us know and we will do our best to make that happen and as always we can always go out on the Pamlico any day - we gotta have excuses to get out of the office some.
     
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