Article on Engineering.com by Michael Molitch-Hou:
In the world of fused deposition modeling (FDM), or fused filament fabrication (FFF) as the technology is called, one family of materials may be considered king of the crop: polyaryletherketone (PAEK). A class of semi-crystalline plastics, PAEK withstand high temperatures while maintaining mechanical strength.
For FDM and FFF 3D printing, PAEK is primarily used in the form of polyether ether ketone (PEEK) filament and its much more affordable alternative polyetherimide (PEI), better known under the brand name ULTEM. Developed by General Electric’s Plastics Division, specifically by Joseph Wirth in the 1980s, PEI is a durable thermoplastic with important physical properties that include high heat, solvent and flame resistance, as well as high dielectric strength, thermal conductivity and overall strength.
After SABIC acquired GE’s Plastics Division in 2007, ULTEM became the property of the largest public company in Saudi Arabia. The material is a more affordable alternative to PEEK, but has a lower impact strength and usable temperature. Perhaps more importantly, 3D printing-compatible ULTEM 9085 has received a number of aerospace certifications that have made it the go-to material when 3D printing performance plastic parts for civil aircraft.
PAEK, PEEK and PEI
As described above, PAEK is strong and resistant to a number of environmental hazards. It has a continuous operating temperature of 250 °C (482 °F) and can even handle loads for a short period of time in temperatures of up to 350 °C (662 °F). When burned, PAEK puts out a low amount of heat and its fumes are the least toxic and corrosive. PAEK also has good chemical resistance.
The material does not break during an unnotched Izod impact test, has a tensile strength of 85 MPa (12,300 psi), a Young’s modulus of 4,100 MPa (590,000 psi) and yield strengths of 104 MPa (15,100 psi) at 23 °C (73 °F) and 37 MPa (5,400 psi) at 160 °C (320 °F).
FFF 3D Printing with PAEK
So far, the number of FFF 3D printer manufacturers that have embarked on the development of PEI and PEEK-capable 3D printers can be counted on two hands. We spoke with representatives from several of these companies to learn how they’d managed to develop printers capable of handling high temperature materials like PEEK and ULTEM. As it turns out, their solutions are trade secrets.
Ben Schilperoort, CEO of Tractus3D, mentioned that one obstacle to overcome while developing the T650P RTP 3D printer involved stable printing temperatures. “Managing the temperatures in the printhead and in the object layers to get them solid are the biggest challenges. That it is why it is hard to print objects with substantial volume and still be strong with high resolution,” Schilperoort said.
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