By Josh Perry, Editor
[email protected]

Researchers at the Virginia Tech University (Blacksburg, Va.) Macromolecules Innovation Institute (MII) have developed a new process that allows for the 3-D printing of Kapton, a polyimide with electrical and thermal properties desired for electronics and aerospace applications.

Daniel Rau, a mechanical engineering Ph.D. student, works with a 3D printer in the Design, Research, and Education for Additive Manufacturing Systems (DREAMS) Lab.
(Virginia Tech University)

According to a report from the university, Kapton can withstand harsh environments, such as those with radiation, high temperatures, and chemical reagents.

“Kapton has a degradation temperature around 550°C, doesn't dissolve in solvents, acts as an electrical insulator, and is resistant to ultraviolet irradiation,” the report explained. “Because the molecule is all-aromatic, containing rings that restrict rotation, Kapton is also very stable.”

The material was only available in 2-D sheets until Virginia Tech researchers used stereolithography to 3-D print it last year. Now, the researchers have developed a second method, direct ink write (DIW), which offers greater flexibility in the ink, synthesis, and the properties of the material. The material is extruded out of a syringe and then hardened by UV light.

“Even after 3D-printing the material via the DIW process, the subsequent parts had similar properties to the commercially available Kapton film,” the article said. “The DIW material has similar mechanical properties up to 400 °C, and its degradation temperature is 534 °C, only slightly lower than the commercial Kapton that degrades at 550 °C.”

The research was recently published in Applied Materials and Interfaces. The abstract stated:

“All-aromatic polyimides have degradation temperatures above 500 °C, excellent mechanical strength, and chemical resistance, and are thus ideal polymers for high-temperature applications. However, their all-aromatic structure impedes additive manufacturing (AM) because of the lack of melt processability and insolubility in organic solvents.

“Recently, our group demonstrated the design of UV-curable polyamic acids (PAA), the precursor of polyimides, to enable their processing using vat photopolymerization AM. This work leverages our previous synthetic strategy and combines it with the high solution viscosity of nonisolated PAA to yield suitable UV-curable inks for UV-assisted direct ink write (UV-DIW).

“UV-DIW enabled the design of complex three-dimensional structures comprising of thin features, such as truss structures. Dynamic mechanical analysis of printed and imidized specimens confirmed the thermomechanical properties typical of all-aromatic polyimides, showing a storage modulus above 1 GPa up to 400 °C.

“Processing polyimide precursors via DIW presents opportunity for multimaterial printing of multifunctional components, such as three-dimensional integrated electronics.”