Polycarbonate is brittle or I am doing something wrong?
July 30, 2020 12:21PM
Hi, I am looking for an advice about polycarbonate, which seems strangely brittle.

I *think* I know how to print PC, at least I can get strong and dimensionally accurate results, at least initially. But the parts which I used for my printer (e.g. hotend mount, bed mounts) crack with time, see my photo.

If in use long enough, they just fall apart along the crack lines. I replace what I can with ABS, and that works very well (though lacks stiffness and temperature resistance).

I use PC for temperature critical parts of my printer, which has a heated chamber reaching 70C (or even 80C). Perhaps, cracking is related to mechanical stress (even minor), like a screw holding the part to a linear rail, and to frequent temperature changes. The filament I use is ICE Filaments PC PRO. I did not try any other PC filaments.

Is the kind of cracking I see normal? Maybe I am unlucky with the filament choice?
VDX
Re: Polycarbonate is brittle or I am doing something wrong?
July 30, 2020 02:25PM
... seems to be "pure" PC, without additives for adjusting physical and longterm behaviour ...


Viktor
--------
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Re: Polycarbonate is brittle or I am doing something wrong?
July 30, 2020 03:58PM
Quote
VDX
... seems to be "pure" PC, without additives for adjusting physical and longterm behaviour ...

Do you suggest that what I see is normal for a virgin polycarbonate, and that polycarbonate with additives would be better?

I have been looking at polycarbonates with additives, they normally print at low temperatures (240-260C), which suggests that they are not very heat resistant...
VDX
Re: Polycarbonate is brittle or I am doing something wrong?
July 30, 2020 04:17PM
... yes - many filaments have additives for better viscosity, optimizing fusing, adjusting shore-hardness ... or other physical properties ...


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
Re: Polycarbonate is brittle or I am doing something wrong?
July 30, 2020 05:00PM
Quote
VDX
... yes - many filaments have additives for better viscosity, optimizing fusing, adjusting shore-hardness ... or other physical properties ...

Not to forget UV resistance! Also, I've noticed that translucent materials get weaker by UV radiation (e.g.: sunlight) much faster than say opaque materials. However I do believe PC is inherently UV resistant like Acrylate. So I don't know if this is additive-related or also present in 'raw' PC.


http://www.marinusdebeer.nl/
Re: Polycarbonate is brittle or I am doing something wrong?
July 30, 2020 05:14PM
I don't have much UV inside the printer.... Can anyone suggest a tried and true PC filament, preferably designed for high temperature applications?
Re: Polycarbonate is brittle or I am doing something wrong?
July 30, 2020 06:19PM
Polycarbonate sheets can be bent cold without cracking, so it should not be brittle, quite the opposite.

I know that PET is brittle if it is printed with absorbed moisture, it needs to be dry, perhaps PC is the same.


[www.hydraraptor.blogspot.com]
Re: Polycarbonate is brittle or I am doing something wrong?
July 30, 2020 07:17PM
Quote
nophead
Polycarbonate sheets can be bent cold without cracking, so it should not be brittle, quite the opposite.

I know that PET is brittle if it is printed with absorbed moisture, it needs to be dry, perhaps PC is the same.

Interesting! I have a feeling that PC is more flexible with absorbed moisture, like nylon. But I did not check it for sure.

EDIT: I dry PC before printing, and print from a sealed drybox with lots of dessicant.

Edited 1 time(s). Last edit at 07/31/2020 06:19AM by Khumarahn.
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