Bad idea to use a print, regardless of how you safety treat the surface. PETG does have fairly strong layer bonds, especially if printed at 100% infill.
However, since printing quality can’t always be guaranteed, it’s always safer to use the print to make a mold and then you can use silicone or epoxies that are safe for this particular use case.
Worst failure case that I have seen that could apply here would be an extruder that intermittently skips. If you have a couple of layers that aren’t printed correctly and not enough filament is extruded, you could potentially have a print split in half at the worst time.
Additionally, especially with cheap filaments, QA is really bad and you probably will not know what additional additives have been used. This could cause strength issues, not be ideal for internal use or completely incompatible with how the surface is treated.
Bad idea to use a print, regardless of how you safety treat the surface. PETG does have fairly strong layer bonds, especially if printed at 100% infill.
However, since printing quality can’t always be guaranteed, it’s always safer to use the print to make a mold and then you can use silicone or epoxies that are safe for this particular use case.
Worst failure case that I have seen that could apply here would be an extruder that intermittently skips. If you have a couple of layers that aren’t printed correctly and not enough filament is extruded, you could potentially have a print split in half at the worst time.
Additionally, especially with cheap filaments, QA is really bad and you probably will not know what additional additives have been used. This could cause strength issues, not be ideal for internal use or completely incompatible with how the surface is treated.
A fully cast model is the best way to go.