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Thread: PVA Question

  1. #1
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    Question PVA Question

    I have been 3D printing since November, getting pretty good with ABS and now PLA. I think it is time to try out PVA for disolvable supports.

    I have read all the warnings about not letting it sit at over 200C for any period of time and plan to print it in the 180-190 range (depending of course on how well it performs).

    My real question is about letting it sit out, hanging on the back of my printer. Is it really THAT sensitive to humidity? I like to print in the evenings, taking the object off the printer in the morning. Is that feasible with PVA? Or must I print, then put the spool immediately in a sealed bag. I am not printing out in my garage, I am in a normal home office that is centrally heated and cooled. How careful do I really have to be?

    Any advice you may have to offer is appreciated.

    Steven

  2. #2
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    This might not help you, however, I have dealt with Taulman Nylon filament. You can't believe how that thing can just soak humidity within a short ammount of time (12 hours in my case) and Taulman claim that it can takes only 8 hours to absorb the humidity in the air.

    I have a spool in PVA sitting in my office and I never print with it. However, I was shocked to see the PVA filament was much more dried than the Taulman filament. Maybe the filament is that old (from 2013 as identified on the label)?

  3. #3
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    Surely someone knows the answer to this. I am just looking for real world information about PVA and moisture absorption. I know that the "books" say to keep it locked away in a low moisture environment, but how sensitive is it, really? PVA is fairly expensive and I am trying to decide whether I should give it a whirl.

    Steven

  4. #4
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    Well, I have yet to mount my spool of PVA. But if how it was shipped to be is any indication as to its susceptibility to moisture absorption, not sure what would be. The reel was lightly shrinkwrapped. That was in a heavy plastic heat sealed bag. All of that was inside a re-sealable heavy mylar type bag. If MakerGeeks thought that it was necessary to double shrinkwrap it and THEN put it in a resealable mylar bag, well, I guess they ought to know how much of a sponge it is.

    When I got it home, I put it (just the way it was shipped) in a 5gal bucket with several 1/2c sachet of silica gel.

    As I said, I don't know how it is yet, haven't loaded it up to print anything as yet. I did snip a sample off and threw it in a room temperature glass of water. It turned to jelly in about an hour and a half. I suspect given supports would be less dense than a snippet of 3mm filament and a much hotter water bath, it would disappear rather rapidly.

    I wouldn't leave an open packet of gelatin sitting out overnight. And given it dissolved nearly as easy as powdered gelatin, I don't think I will leave my spool of PVA sitting out either.

  5. #5
    Technician postmahomeson's Avatar
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    actually i have made a similar plastic in milk form if you want i can send you the lab report on my science initiative if you want but i got to you warn you, your going to want to have ventilation and not hang around the experiment all day but it's approved by my high school's science teacher which had to review it in order to approve because his employer has the chemical educator permit / i invented by the chemical process from scratch alone to try and impress the science teacher i got the file on my google drive https://docs.google.com/document/d/1...frPtHsfipk/pub
    warning at your own risk but i did however have to do research to ensure safety prior to first attempt
    Last edited by postmahomeson; 04-03-2015 at 01:48 PM.

  6. #6
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    PVA sucks moisture badly. Depending on where you live, if you live in coast area, you got to store it carefully when not printing. Overnight with high humidity could cause problem.

  7. #7
    PVA does absorb moisture like you wouldn't believe. You may have bought PVA from home depot or somewhere like that before, to use as a glue or to water it down and paint with it and use it like a sealant. If you've ever done that then you'll know just how water soluble this stuff is, which is kind of a big clue as to why this stuff so readily takes up moisture. Anything that's water soluble will do that.

    I found that I had much more success when printing with HIPS for dissolvable supports, but there are a few things you should be aware of. Firstly Limonene, which whilst it may be organic and smells wonderful, is highly flammable and has a very low flash point (not good). Once you're happy that the environment that you're going to be using it in is relatively safe (no blow torches or soldering irons in your printing space, and you're a non-smoker) then it's not as noxious to work with compared to other solvents if you're careful, but you do need to take care use precautions to avoid skin contact and keep your hacker space well ventilated. It's actually useful as a cleaning and degreasing product on it's own and does have some other uses aside from just dissolving HIPS, and it's not too hard to get hold of.

    The other issue is of the types of filament that it will dissolve. Some will tell you that it won't dissolve ABS but will dissolve PLA, others will tell you that it's the other way around. The truth is that there is so much filament around isn't always strictly what it says it is on the tin. So, make sure you test your filaments in Limonene first - just get a jar and drop some filament in there and leave it for 48 hours - you should get a pretty good idea as to what resists it and which ones will dissolve. I've had both ABS and PLA filaments dissolve in Limonene, but not all ABS and not all PLA. I've no idea how amphora (Colorfabb XT filaments) behaves with Limonene yet as I've not tried it.

    Also, you may find that the rate at which HIPS dissolves isn't particularly quick and that after 48 hours the filament you thought was resistant may even start to soften. For that reason I would recommend an ultrasonic bath (a steel one) which aren't too expensive and will greatly accelerate the process, providing that your prints are sufficiently robust enough to endure it.

    A great test is to print a Hilbert Cube in a suitable non-dissolvable filament of your choice, combined with HIPS.

    HIPS is not too bad to print with either. It prints a lot like ABS and is much more stable and less messy and with much less stringing than PVA. HIPS is useful for other applications, not just support material, unlike PVA.

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