PET-G Thermoforming and Heat Treatment Safety
I am not sure if this is the correct place to post this, so if there is somewhere more appropriate please let me know. I am planning on using PET-G in a project similar to this 3D printed arm brace. https://www.instructables.com/3D-Pri...ization-Brace/ The manufacturing process involves submerging the 3D printed part into a pot of boiling water to heat the plastic to its glass transition temperature, then molding it around an object like a person's forearm so that as the part cools it accurately conforms to the arm's dimensions. After that I want to use my oven to heat treat the PET-G to improve its impact resistance. Before doing any of this, I want to ensure this process won't release any harmful vapors or carcinogens during manufacturing. I know PET-G is safe to print without ventilation and is considered food safe. However, is PET-G safe to thermoform and heat treat? Thank you for your help in advance.
RE: PET-G Thermoforming and Heat Treatment Safety
PETG won't out gas at the glass transition temp (around 200 --> 250 c, depending on the composition). I don't think boiling water is going to soften PETG, it is only 100 C.
A 450 degree oven will do it.
RE: PET-G Thermoforming and Heat Treatment Safety
Glass transition temp for petg starts at around 75c depending on brand and from the Prusa article on annealing they reckon 90-110c is a suitable temp so boiling water is right in the sweet spot. Pretty rough on whoever's arm you are using though 🙂
You are safe on the outgassing. If you have printed it already then heating it up to annealing temps isn't going to do much at all.
RE: PET-G Thermoforming and Heat Treatment Safety
@neophyl
I did not know that you can't put PETG in the dishwasher (70c) - I do that all the time - and it doesn't soften or melt. Maybe I don't understand the term glass transition. I assumed it meant melting point.
RE: PET-G Thermoforming and Heat Treatment Safety
The manufacturing process involves submerging the 3D printed part into a pot of boiling water to heat the plastic to its glass transition temperature, then molding it around an object like a person's forearm so that as the part cools it accurately conforms to the arm's dimensions.
PETG won't mould unless at temperatures that are likely to cause burns/scalds. Is it possible to take a cold mould and make a cast of the arm to mould around? Or work with PLA, scan the tailored PLA and reprint the scan in PETG?
After that I want to use my oven to heat treat the PET-G to improve its impact resistance.
PETG is not going to gain much from annealing, better to design a stronger shape or a thicker part.
Before doing any of this, I want to ensure this process won't release any harmful vapors or carcinogens during manufacturing.
Natural/clear PETG will be fine. Colours might cause problems unless you can identify the pigments and get safety data on them.
Another possibility is to make a strong outer scaffold and join it to a tough, mouldable liner; it would be worth experimenting with TPU Flex.
What are you designing?
Cheerio,
RE: PET-G Thermoforming and Heat Treatment Safety
@dan-rogers
Glass transition temp is when it becomes soft but not at the melting point. Prusa did an article on annealing here that also explains GTP https://blog.prusaprinters.org/how-to-improve-your-3d-prints-with-annealing_31088/#:~:text=PETG%20was%20annealed%20at%20110,a%20tougher%2C%20heat%20resistant%20extruder. but CNC Kitchen also did at least one video about it previously that was quite interesting.