Polycarbonate

From RepRapWiki
Jump to: navigation, search

Contents

PC - Polycarbonate

Polycarbonate is a thermoplastic, it's strong and impact resistant (It's used in the making of bullet proof glass and compact discs) temperature resistant and it can be extruded (at the right temperature). It can be bent and formed while cold without cracking or deform and it is also very optically 'crystal' clear to visible light (opaque to UV light), but it's actually not very easy to keep it clear during extrusion, see below -

Don't confuse Polycarbonate with Acrylic or Plexi-glass, they shatter and crack, Polycarbonate tends to just bend and deform and after much effort will eventually stretch like very hard rubber until it eventually breaks.

Polycarbonate has a glass transition temperature of about 150 °C (302 °F), so it softens gradually above this point and flows above about 300 °C -> Wikipedia

For more details, see the Wikipedia entry on Polycarbonate

Usage

See also Printing Polycarbonate

Polycarbonate is an interesting material for 3D printing, as an engineering material for parts submitted to loads. It is easily extruded using common extruder drive systems with all metal hotends. To limit problems with bed adhesion and warping, formulations adapted to printing may be used.

  • From Pistol

PC warps significantly. Do not attempt without a heated bed.

Solvent Welding

Polycarbonate can be solvent welded with ketones such as acetone, but dichloromethane (DCM) works better, forming very strong bonds. The build-plate-facing surface of the print, being very smooth, works best. Do not use as much DCM as you use acetone when solvent welding ABS: according to the Plastics Joining Handbook, excessive solvent leads to bubble formation and a weaker bond. Just enough to wet the surface of the object is sufficient. In industry, a felt pad shaped to fit the surface to be welded and moistened with DCM is sometimes used to rapidly an uniformly apply the solvent.


Dichloromethane is also suitable for vapor polishing PC prints, if great care is taken to contain it. It has a quite low boiling point, evaporating quickly near room temperature.

DCM has greater toxicity than acetone. 3D printing uses should not result in the production of significant amounts of DCM waste, but it should be noted that it is harmful and generally illegal to put DCM down the drain.

Safety Issues

  • From Pistol

Word to the wise on safety. It seems that PC produces a lot of micro-fine particles, more so than ABS. These particles accumulate on the underside of the print-head. If they accumulate there, then they are likely in the air as well. Work in a well-ventilated area or install some ventilation. On a side note, try not to stare too closely to the object being printed. After a while it stings the eyes.

If using dichloromethane for solvent welding, or, especially vapor polishing, be very careful to avoid breathing the solvent fumes. They are hazardous. Research appropriate protective measures to avoid exposure.

Heater Settings

Depending on the speed that you extrude and the size of the filament the hot-end may require settings of the following -

1.6mm filament tested - by RichRap

A heated bed was used at 85 Degrees C. The bed was covered in PET tape and then Kapton to top of that.

I've had success using a 130 deg. C. heated bed a thin coating of Wolfbite Mega on a clean mirror, in conjunction with an enclosed printer and a chamber temperature of 60 deg. C. Higher chamber temperatures might further reduce part delamination and warping, but it hasn't been tested by me.

A RepRap Prusa Mendel was used along with a Wade Accessible Extruder (Greg Frost) (Greg's Hinged Extruder?) and hobbed bolt designed for 1.75mm Filament.

@ 30mm/Sec print speed you can go down to as low as 255 Degrees C without the extruder jamming, but really 265 should be used as a minimum.

@ 60mm/Sec print speed you need around 285 Degrees C constant hot-end temperature

@ 80mm/Sec the temperature needs to be 295-300

@ 120mm/sec a temperature of 305 Degrees C was used (Maximum for the hot-end being used), but infill was sparse with breaks and solid layers had holes so higher temperature may be required.

The extruded filament behaves more like ABS than PLA and bonds very well together, strength seems to be similar at all the above temperatures and speeds.

It was observed that the faster and hotter an object was printed the more clear the end results, these were still closer to white than clear.

Moisture Issues

PC is very hygroscopic and will absorb moisture from the air, this can make some filaments have issues when being extruded, usually bubbles, oozing of filament when not desired and poor print quality. The uncovered PC filament was in free-air for many days while testing and other than a 'snow-white' effect to the finished parts moisture was not observed to cause significant issues - more testing on this needs to be done.

A test of drying the filament before is needed to see if the 'snow-white' effect can be minimised.

Other suggestions have included the transition of the filament from being amorphous (Clear) to semi-crystalline in structure, it would be nice to prove this in some way.


  • From Pistol

In humid environments such as the coastal areas, PC can absorb enough moisture in a 24 hour period to become unprintable. Be sure to keep PC in an airtight container DURING long prints.


Warping Issues

  • From Pistol

PC tends to warp more than other materials such as ABS or PLA. Various methods have been tried to fight warping. Some users experience success with a Garolite heated bed or using ABS juice on glass. Pistol has determined that the best method is superglue on cool glass and then heating the bed to 125C - 130C.

Word to the wise on safety, when Superglue warms up it will release toxic fumes! Work in a well ventilated area or better yet, setup a ventilation system.

Delamination

  • From Pistol

Once the separation from the heated print bed is solved, you'll notice that the core issue hasn't gone away. Instead you'll notice delamination occuring between layers. This is because the shrinking effect on the cooling material is still occurring. I suggest using more permimeters (4 or more) when slicing and to also use a concentric 100% infill. The concentric infill allows for maximum adhesion from one layer to the next by lining up all the paths made from the extruder.

Support structures

  • From Pistol

The latest problem to be solved is adequate support structure. Structures are used to give support to the print, but when printing with PolyCarbonate the structure needs to perform double duty. It also has the hold the print down to the bed. Warping will pull the weak support structure apart and ruin the print. Any ideas to fight this issue are welcome.

A heated chamber is very effective at addressing any delamination issues. I have tested a 60C chamber. Higher temperatures are probably better if the components of your printer can handle it.

Availability

See Printing Material Suppliers. You can sort the tables there by material.

Known vendors
Printer Playground

Modified polycarbonates

In order to reduce the warping and the printing temperature, some manufacturers propose modified polycarbonate. The compromise is that the resistance to temperature of this modified plastics is reduced, unfortunately, manufacturers have not published temperature data (as of April 2016). They also have improved adhesion on bed (heated).

  • ePC from Esun (China) is available since the end of 2015. This was well received by test users [1]
  • PC-plus from Polymaker (China) developed with chemist Bayer (Germany) [2]. Available from October 2015

Polycarbonate Plastic Blends

PC-ABS is also to be tested shortly, results will be added. The intention with most blends of PC is to lower the required extruding temperature. PC-ABS blends are common in the automotive industry and combine the strength and heat resistance of PC with the flexibility of ABS.

PC-Polyester could also be tested.

References

  1. http://forum.makergear.com/viewtopic.php?f=11&t=2592 Thread on MakerGear forum
  2. https://www.youtube.com/watch?v=JsrIhMF0yP8 Film about resistance comparative test, without values

External Links

Further reading