'Hi, I'm Tom (@TomHe). I'm a Material Engineer at Ultimaker, I started in 2015 as an intern to finish my Chemical Engineering Master from Eindhoven University of Technology.' ...
Tom has worked for Ultimaker for 3 years already and has played a role in many of the Ultimaker products we all use regularly. Tom started in 2015 working on PVA. His graduation project evolved around producing and 3D printing carbon nanotubes, and graphene filled materials (for electrical conductivity). Other responsibilities Tom joyfully carried; the first print profiles for the Ultimaker 3 and everything PVA related. Putting together 3D print profiles also include determining the best nozzle geometry, Cura features and supplying values for all settings used in Cura.'
Tom will start replying at 4.30pm CEST.
When PVA is exposed to humidity, water molecules slowly creep into the polymer structure. Because the water molecules are really attracted to the polymer chains, this happens faster with PVA than with our other materials. The water molecules actually push the polymer chains apart, decreasing the effective glass temperature of the material. When too much water is absorbed, the material becomes moldable at room temperature and the filament will melt together. Wet PVA prints with a lot of bubbles, and will look more cloudy. It prints less reliably as it can get stuck in the feeder.
If you dry the filament in time (before it’s too wet) you can easily print with it again. Drying should be done at ~50-55C for about 1.5 - 2 hours. I always put my spool in a cardboard box on top of a hot build plate. The box is just there to trap the heat. You shouldn’t use a household oven as those aren’t meant for these ‘low’ temperatures (and aren’t meant for heating plastics). If you heat it too hot, it can deform. And wait for the filament to cool down to room temperature before printing, otherwise the feeder could deform the PVA.