Shelf Life of PVA after package is open? Printing poorly over time...

[strongbad71 0]

I have used PVA dissolvable material in my S5 for awhile.  However, with this spool that was fine initially, it now is starting to flow poorly, not stick as well to the glass, and is badically looking ragged instead of smooth.  All the same settings.

 

The only thing that helped a little bit was increasing the temp by 15C, but still is quite poor.

 

So, I am wondering if this material degrades over time when the plastic wrapping is removed and exposed to air?  

 

 

[gr5 1,734]

PVA absorbs water from the air and when it does it goes bad quickly.  At normal typical 50% humidity the last meter of filament (outer part on spool most exposed to air) goes bad in as little as 10 hours.  In northern climates in the winter it can last several weeks.  It also matters on the manufacturer as Ultimaker PVA supposedly lasts longer than most.

 

If it's in really bad shape it will steam at pop and crackle as you print.  You can see the steam coming out.  But even without that it might have enough humidity to degrade performance.  PVA comes out snowier when it has water in it and more clear/transparent when it is dry.  If it's too dry it can actually crack but this is not a common problem.

 

To dry your PVA take a small piece and put it on the heated bed with a towel or two over it and try 60C, 70C, 80C, 90C and see where it gets soft - if you bend it and it stays in the new shape.  Then set the bed to just at this temp or slightly below and dry the whole spool with a 8 inches/200mm of blankets or towels on top for 8 to 20 hours.  If you are in a rush and only need to print a few meters then you can unspool that much, put it on the bed with spool on top and heat it for just an hour or two.  Again with at least one towel on top.

 

[RudydG 60]

Like GR5 says, pva does not need much more then 10hrs exposure to the environement to become "bad"

I only unwind the needed length from the spool, the rest of my pva goes directly back in a sealed bag with silica gel.  For really big jobs, i use a drybox. But it you leave pva to long in the drybox (under 20% RH), the pva becomes to dry, and starts to be brittle.

So, if you don't use the pva, put it in a sealed bag with its initial silicagel. Best practice 😉

[strongbad71 0]

Sorry, didn't get a notification that there were responses...   So yeah, it is printing like 'snow', and very crumbly.  

 

Too late now I suppose, but next reel I will use it in chunks and airseal the spool.  Now I know!  Thanks!