Sunlu PETG-CF Filament 1.75mm 1kg

PETG with 10% chopped carbon fibre through it. The fibre stiffens the print and takes the gloss off, so parts come out with a dry, slightly speckled matte surface that hides layer lines — and it does that without the brittleness that usually comes with a filled filament.

That last part is the interesting bit. Most carbon-fibre filaments trade toughness for stiffness. This one holds 30% elongation at break and 20 kJ/m² notched impact in the X–Y plane, which is properly tough for a CF material. Good for functional brackets, housings, tool holders and anything that needs to survive being dropped.

At a glance

Worth knowing

Tough for a carbon-fibre filament, and that is the reason to pick it. 30% elongation at break and 20 kJ/m² notched impact are figures you would expect from unfilled PETG, not a CF blend. If you have been burned by a carbon-fibre filament that shattered on the first knock, this is the one to try.

Orient load-bearing parts deliberately. Impact strength is 20 kJ/m² in X–Y but 5.5 kJ/m² in Z–X — roughly a quarter. Layer lines are the weak axis by a wide margin here, so put the load across the layers rather than along them.

Sunlu do not specify a nozzle material, but we recommend hardened steel. Their data sheet is silent on it. Carbon fibre is abrasive regardless of what the sheet says, and it will open up a brass nozzle's bore over time — you tend to notice extrusion width drifting before you work out why. A hardened nozzle is cheap insurance.

Heat resistance is modest: 70°C heat deflection at 0.45 MPa and a 65°C glass transition, so this is not the filament for a car dashboard or anything that sits in direct sun. It is amorphous, so there is no melting point to quote — it softens rather than melts. Decomposition is above 425°C, well clear of printing temperatures.

Storage

Sunlu specify that once the spool has been open and exposed for more than 48 hours, dry it at 70°C for 4–6 hours before printing. Keep it sealed with fresh desiccant between jobs.

As filament takes on moisture you'll hear popping or hissing at the nozzle, then see stringing and rough surfaces, and eventually the strand goes brittle enough to snap in the tube. That's almost always moisture, not technique — dry it and it usually comes back.