What is the thermal conductivity of various 3D printing filaments? Thermal conductivity is how well a plastic conducts heat. Most plastics don't conduct heat very well at all, which is what allows them to be 3D printed. That being said, there are a lot of potential use cases for highly thermally conductive filament, assuming you could print them. A commonly discussed one is computer heatsinks. Similar heatsinks could also be used for stepper motors and extruders in 3d printing. 

To get a good picture which plastics are useful in such an application (like mentioned in question: "Water-cooling stepper motor with aluminum block"), I need to know what is the thermal conductivity of the commonly used thermoplastics.
All values are in W/(m*K).


PLA: 0.13
HIPS: 0.20
ABS: 0.25
PETG: 0.29
PEEK: 0.25
PLA with copper: 0.25 (see discussion) 
PETG with 40% graphite: 1.70 (ansiotropic)
TCPoly: 15
Steel (not a 3dprintable plastic): 10 - 50