PETG vs PCTG vs PET-CF: The Polyester Family Explained

Three Letters Apart, Three Different Materials

PET is the plastic of water bottles: strong and chemically resistant, but it crystallizes as it cools, which makes plain PET hard to print. Manufacturers get around that two ways. Modify the chain so it stays amorphous (PETG, PCTG), or accept the crystallinity and add carbon fiber to control shrinkage (PET-CF). The two routes produce very different materials.

Side by Side

Typical printed-part values; exact figures vary by supplier.

PETG: The Reliable All-Rounder

PETG adds glycol to the PET chain, which stops it crystallizing. The result prints easily, bonds layers well, resists many chemicals and handles heat up to about 80 °C. It's the default functional material for good reason. Its weak points are surface scratches and moderate impact strength.

PCTG: PETG, But Tougher

PCTG uses a different glycol (cyclohexanedimethanol) in larger proportion. It prints just like PETG but has several times the impact strength and better clarity, with similar chemical resistance. Heat resistance is similar or slightly lower. If a PETG part has ever cracked when dropped, PCTG is the direct fix at little extra cost.

PET-CF: The Stable, Stiff Composite

PET-CF keeps PET's semi-crystalline structure, which is what gives it much higher stiffness and heat resistance than PETG. The carbon fiber controls the shrinkage that makes plain PET hard to print. It also absorbs very little moisture, so it's one of the most dimensionally stable composites available. It's a strong alternative to nylon-CF for fixtures and brackets that have to hold tolerance in humid environments. The trade-off is lower impact toughness, as with every fiber-filled material.

Which One?

• General functional parts, containers, brackets indoors: PETG.
• Parts that will be dropped, struck, or need clear walls: PCTG.
• Stiff fixtures, gauges and brackets that must hold dimensions, or run warm: PET-CF.
• Outdoor parts in direct sunlight: none of these; choose ASA or ASA-CF.

Get a Quote

All three are selectable on the quote page under FDM. Upload your part, switch between PETG, PCTG and PET-CF to compare prices instantly, and add a note if you'd like our engineers to confirm the choice.