Under Protolabs’ video on Nylon PA 12, a viewer asked what he called a stupid question. Since the material is melted together, is there an environment, temperature or substance that would break the bond and turn the part back into powder? It isn’t stupid. It’s the PA12 chemical resistance question every fluid-handling customer should ask, just phrased backward.
What does PA12 chemical resistance actually cover?
Oils, fuels and most common solvents, and nothing in HP’s published tests turned a part back into powder. HP’s datasheet for HP 3D High Reusability PA 12 claims excellent resistance to oils, greases, aliphatic hydrocarbons and alkalies. Its footnote lists what was tested: alkalies, chlorine salts, alcohol, esters, ethers, ketones, aliphatic and aromatic hydrocarbons, toluene, unleaded petrol, motor oil and DOT 3 brake fluid.
HP’s fluid tightness white paper rates most of that list “no effect.” Three entries get “moderate effect”: hot water, chlorinated hydrocarbons and trichloroethylene.
What happened when HP soaked MJF parts in car fluids?
HP’s 2018 paper on automotive fluids immersed printed tensile bars at 60 °C for 4 to 6 weeks. Motor oil, gear oil, steering fluid and grease didn’t attack the PA12. Brake fluid added about 2% weight without acting as a plasticizer.
Antifreeze was the one that changed things. Bars soaked in a 50/50 coolant mix gained 3.32% by weight, lost tensile strength and stiffness, and stretched further before breaking. HP’s conclusion: antifreeze plasticizes PA12. Even so, no sample showed a chemical reaction, stress cracking or solvation.
So what would turn it back into powder?
Nothing in those reports. Heat melts PA12 rather than crumbling it, and HP lists the powder’s melting point at 187 °C. Notice what’s missing, though. Neither HP list includes acids, so if a customer’s part will see one, you have no HP data to point to.
HP’s own paper carries the caveat that matters most: no short-term test can simulate every end-use environment, and testing production parts is the only definitive check.
How do you check a fluid HP didn’t test?
Print six tensile bars in one build. Weigh three, soak them in the customer’s fluid at its service temperature, and keep the other three dry beside them. After the soak, weigh and pull all six. A weight gain with lower strength and more stretch is the antifreeze pattern, and it’s worth a call to the customer before you quote.
Related on the Solvi blog: MJF Watertight Parts: Can PA12 Hold Water Under Pressure?; MJF PA12 Heat Resistance: Will a Thin Part Survive 60 °C?; PA11 vs PA12 on MJF: When Is PA11 Worth Running?.
Sources: YouTube: Nylon PA 12, 3D Printing Materials Explained (Protolabs), viewer question; HP 3D High Reusability PA 12 datasheet (PDF); HP: Chemical compatibility of HP 3D HR PA12 with automotive fluids (PDF); HP white paper: Fluid tightness characterization I (PDF).