Today I tested if any of the most popular filaments would dissolve in water and also if they would dissolve in saltwater. I know that all 4 of these filaments will hold up in regular water already but it doesn’t hurt to have control samples to compare the saltwater tests with.
There are many practical applications for 3D printed parts to be in water or saltwater such as aquariums, pools, and ocean applications. There are plenty of filaments that seem to stand the test of time out of the water but which ones will hold up in the water?
Of the 4 most common filaments PLA, PETG, ABS, and TPU, only PLA dissolves in saltwater over a long period of time. Most 3D printing filaments do absorb water to some degree but not a significant amount to make a difference dimensionally.
The Experiment.
To test the effect of water and saltwater on different materials I printed out 8 calibration cubes, 2 of each material (PLA, PETG, ABS, and TPU). I then placed one set of the cubes in regular drinking water and the other set in salt water for one month and collected another reading.
I also measured the length, width, and height of each block throughout each stage of the process to see if there was any absorption or dissolving of the material throughout the test.
I will be updating this article once I collect data from the 6 months and one-year mark.
I placed the calibration cubes in the cups with water and weighed them down with some garden rocks to keep them submereged.
There are a few factors that I did not have in consideration in my test obviously. I know there was not any running water for this experiment and also there was no algea or bacteria like there would be in a fish tank.
Here is a consolidated table of my findings for the calibration cube submerged in water.
| Duration in water | PLA | PETG | ABS | TPU |
|---|---|---|---|---|
| Original Reading | 20.05 x 20.01 | 20.06 x 20.02 | 20.05 x 20.03 | 20.05 x 19.93 |
| One Month | 20.05 x 20.03 | 20.10 x 20.05 | 20.09 x 20.06 | 20.04 x 19.94 |
| Six Months | TBD | TBD | TBD | TBD |
| One Year | TBD | TBD | TBD | TBD |
Here is a table of my findings for the calibration cube submerged in saltwater.
| Duration In Saltwater | PLA | PETG | ABS | TPU |
|---|---|---|---|---|
| Original Reading | 20.03 x 20.00 | 20.06 x 20.02 | 20.04 x 20.02 | 20.06 x 19.95 |
| One Month | 20.05 x 20.02 | 20.08 x 20.03 | 20.07 x 20.02 | 20.08 x 19.94 |
| Six Months | TBD | TBD | TBD | TBD |
| One Year | TBD | TBD | TBD | TBD |
Does PLA Dissolve In Water Or Saltwater?
PLA does not dissolve in saltwater. Even when left in water for over 30 days there is no dissolving in the material. PLA is a common material to use in fish tanks as well as planters. PLA does slightly absorb water but a significant percentage by mass.
There were also no visible signs of degredation. The physically felt exactly the same as it did before being soaked in water. I can not see any layer’s seperating or edges that were disolved.
The PLA before being soaked and after being soaked are virtually the same besides the small amount of water that was absorbed.
PLA – Original Reading – Water
PLA – One Month – Water
PLA – Original Reading – Saltwater
PLA – One Month – Saltwater
Does PETG Dissolve In Water Or Saltwater?
PETG does not dissolve in water or saltwater. PETG is not biodegradable which is great for underwater applications because bacteria will not degrade the material over time. PETG has high water resistance and is a common and recommended material for aquariums and underwater components.
Similar to PLA, PETG absorbed some water which made it grow dimensionally. PETG is one of the most stable filaments dimensionally so the growth when left in the water was kind of surprising to me.
The PETG performed very well in water and saltwater. there were no visible signs of degradation or deterioration ant the material felt as strong before and after being left in the water.
There were also no signs of layer separation or any dissolving on the edges.
PETG – Original Reading – Water
PETG – One Month – Water
PETG – Original Reading – Saltwater
PETG – One Month – Saltwater
Does ABS Dissolve In Water Or Saltwater?
ABS does not dissolve in water or saltwater. ABS is not biodegradable so it will not be broken down by bacteria and algae. ABS is a more controversial material for aquariums due to its toxins and potential to harm the fish in the aquarium. Some select brands of ABS are aquarium safe but use caution.
ABS absorbed about the same amount of water as PETG. I did not expect to see any change in ABS when left in water.
ABS Performed well in the water as well as the saltwater. There were no signs of dissolving or degradation on our test samples and the material still felt very strong. There were also no signs of layer seperation (except the very small amount of layer seperation that was already there).
ABS – Original Reading – Water
ABS – One Month – Water
ABS – Original Reading – Saltwater
ABS – One Month – Saltwater
Does TPU Dissolve In Water Or Saltwater?
TPU does not dissolve in water or saltwater in the right environment. TPU is technically a biodegradable and recyclable material but it has great water and oil-resistant properties. ABS is safe to use in aquariums as well underwater components that require flexibility.
TPU did not dissolve as much water as I expected. I thought that TPU would absorb more water than PLA, PETG, and ABS but it turns out the opposite was true and TPU absorbed very little water.
TPU did not show any signs of degradation or deterioration and still felt as strong as it did before being left in water or saltwater. There were also no signs of layer separation.
TPU – Original Reading – Water
TPU – One Month – Water
TPU – Original Reading – Saltwater
TPU – One Month – Saltwater
Conclusion.
Most of the common filaments that we use regularly have very good water and saltwater resistance. PLA, PETG, and ABS did absorb a small amount of water which made them grow in size and TPU stayed dimensionally the same over one month.
