Kapton, a material used in electronics and aerospace applications, has only been available in sheet form. Researchers from Virginia Tech have found a way to 3D-print a polymer with Kapton's structural characteristics.
Engineers like Christopher Williams are very familiar with Kapton.
At times mistaken for “gold foil,” the insulating material is often cloaked around spacecraft, satellites, and planetary rovers to protect components from the extreme conditions of space. The polyimide film, developed by the Wilmington, DE-based polymer manufacturer DuPont, provides temperature stability and flame resistance to electronics and aeronautics parts.
Kapton is composed of carbons and hydrogens housed within benzene rings. The molecular structure imparts the coating with exceptional characteristics, including thermal and chemical strength, high electrical resistance, and UV-radiation shielding.
The material, however, is notoriously difficult to produce in any format other than thin sheets.
As an alternative to literally wrapping existing structures with the DuPont polyimide, Williams and fellow researchers from Virginia Tech have found a way to 3D-print a polymer with Kapton’s chemical structure and performance. The achievement, says Williams, ushers in entirely new applications where engineers can, for the first time, create specific shapes or structures from the high-performance material.
The properties of Kapton have always made the polymer an unlikely candidate for 3D printing. For starters, the polyimide is fixed in its molecular structure, is not soluble, and does not melt.
“Everything about this material says it’s not processable,” said Williams, an associate professor with Virginia Tech’s Department of Mechanical Engineering leader of the Design, Research, and Education for Additive Manufacturing Systems (DREAMS) Laboratory, who spoke with Tech Briefs.
Creating a Kapton-like material required a convergence of two very different research areas: manufacturing and molecular chemistry.
Williams teamed with Timothy Long, a Department of Chemistry professor and director of the Macromolecules Innovation Institute (MII). Through a synthetic process, Long and his lab created the system’s “heart and soul,” a precursor material called an organogel.
The researchers, led by Long, synthesized macromolecules in a solvent, allowing the particles to remain stable and maintain their thermal properties for processing in 3D printing.
The soluble precursor polymer contained photo-crosslinkable acrylate groups, enabling light-induced, chemical crosslinking for spatial control in the gel state. Printed quickly with light, the organogels formed with sufficient modulus and strength.
By adding a post-printing thermal treatment – heating the gel in an oven essentially – the finished product was transformed from a crosslinked precursor polymer to a material with all the capabilities of Kapton.
Virginia Tech’s new polymer maintains its properties above 680 degrees Fahrenheit. The increased temperature stability supports the requirements necessary for the extremes of space environments.
“For all intents and purposes, when we characterize this material, it has all the physical properties – very high temperature stability, degradation stability – and the same mechanical properties, in terms of modulus and elongation, as Kapton,” said Long. “The molecular structure is like Kapton, but it’s not Kapton, because Kapton is a film.”
Theoretically, the high-performance polymer could be made into in any shape or size that a design engineer desires. So far, the university researchers have printed small chess pieces and lattice bricks – structures already more complex than a thin sheet.
A Next-Generation Collaboration
In addition to teamwork among the professors, the 3D-printing process demonstrated a collaboration between molecular science students and engineering students – the kind of partnership that Williams sees leading a new wave of technology development.
“What excites me is what they represent: this next-generation scientist/engineer who can speak both chemistry and manufacturing,” said Williams. “They represent the future of what science and engineering will be. You have to have both to really make a contribution.”
Long, working with graduate students and then-post-doctorate researcher Maruti Hegde, now a research associate at the University of North Carolina at Chapel Hill, derived the novel polymer synthesis design, allowing the polyimide to be additively manufactured.
Williams’ lab, led by College of Engineering doctoral students Viswanath Meenakshisundaram and Nicholas Chartrain, then refined the process for 3D printing. For a year, the teams collaborated, testing the material’s performance in extreme temperature scenarios and fine-tuning the printing method.
Williams’ and Long’s work recently was published in the Advanced Materials Journal: Processing the Nonprocessable.
With a brand-new way to create Kapton-like materials, Williams and Long envision new possibilities, including the ability to print nanosatellites and other smaller components required for deep space exploration – parts that cannot be delivered quickly and easily from Earth.
The team also sees the process as a valuable one for the field of printed electronics, where electronics systems are created with the electrical components and interconnects already embedded.
The duo, however, know that they are in new territory, and anything is possible. The 3D-printing process, said Williams, allows designers to think differently of what can be achieved with high-performance polymers.
“Engineers aren’t used to thinking about using this material to design products. We’re only used to designing a product and then wrapping it in this foil,” said Williams. “The fun part now is to actually show this to a designer and get them to start dreaming about what is possible.”
What do you think? Can this 3D-printed polymer support space missions? What applications do you envision? Share your thoughts below.