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Our nylon material specifications include mechanical properties and data for both "wet" and "dry" conditions. This dual presentation is necessary due to nylon's highly hygroscopic nature, meaning it readily absorbs moisture from its surroundings.
You may be aware that you need to keep your nylon filament dry while on the spool to get proper printing. When your nylon filament absorbs too much moisture, you will hear "popping" and "cracking" when extruding and your print will have a lot of very hard to diagnose defects.
Just as your nylon is expected to absorb moisture while on the spool, it will also absorb moisture as a final print.
The process is inevitable as moisture is absorbed by the print by the surrounding humidity in the air. This means that your nylon print will grow slightly post annealing as it absorbs moisture. This also means your nylon print will get less rigid but will also become more impact resistant.
How much your print will be affected by being moisture conditioned will depend on the type of nylon you printed with. We developed Fiberon™ PA12-CF10 with the intention for it to have a lower moisture sensitivity when compared to PA6/66 and PA6-based materials.
You will see on our Materials App page for Fiberon™ PA12-CF10 that the data does not change much when you click on "Wet", due to it being less susceptible to moisture than the other nylon options. This is particularly noticeable when you compare it to Fiberon™ PA6-CF20.
Affect on Material Properties:
As mentioned earlier, and as you can see on our Materials App, absorbing moisture will cause your part to be more ductile and more impact resistant. This means that a moisture conditioned nylon print will be less likely to break when hit but will also be more likely to bend under pressure.
You will notice that all properties related to stiffness and impact resistance will change. When wet - the printed part will have lower tensile strength and a lower bending modulus, but it will also have a higher Charpy impact strength and higher elongation at break.
Affects on dimensional accuracy:
Since your part will be absorbing moisture - it means it will "grow". How much it grows will depend heavily on which nylon you print with, how large your part is, and how dense your part is. Below are some test results by the Polymaker team:
40mm Cube, 100% Infill, after annealing, before moisture conditioning:
And then the same print after moisture conditioning:
In the above example - you will see that after annealing the parts shrunk slightly, which is why you see a negative number. When you anneal your print, you will dry out any moisture that may remain in the print, causing the print to very minorly shrink.
You will then notice that after moisture conditioning, most prints grew past their original size, with the exception of Fiberon™ PA12-CF10. This is expected due to the moisture that is being absorbed, and also another reason to try Fiberon™ PA12-CF10 if your goal is to use a strong nylon blend but maintain your dimensions.
Unfortunately we are unable to give a "standard" for dimensional change for each material since it will heavily depend on your models geometry, size, and infill density, but you will need to factor in these dimensional changes if your goal is to have a print with the most precise dimensions possible.
How to Moisture Condition
All of our nylon options should be annealed before moisture conditioning. Annealing is very important to do with our nylons due to our Warp Free Technology.
You can read more about the annealing process HERE.
Annealing will dry your print out, so if you anneal after moisture conditioning, you will just need to moisture condition again.
There are a few options to moisture condition:
1. Place print in humid climate for 48 hours. This means using a humidifier in a small room where the print is located. Another method you can use is keeping the print in a Tupperware container locked with a wet sponge. The wet sponge will slowly release moisture and the print will slowly absorb it.
2. Submerge your print in water, and then let sit out for 48 hours. After you dunk your print in water it will absorb more moisture than equilibrium with the environment, so it will slowly dry out. It would be smart to leave a wet print out for 48 hours for it to equalize.
3. Leave your print out for 2 weeks in the environment. This process means you basically do not need to do anything other than to leave the print out. The print will slowly absorb moisture from the humidity in the air until it becomes properly moisture conditioned.
Some individuals have attempted to prevent moisture conditioning by spraying with automotive spray paint, though we have very limited information on this. Generally, moisture conditioning a nylon part will be inevitable over time.