3 years ago

3D Printing All-Aromatic Polyimides using Mask-Projection Stereolithography: Processing the Nonprocessable

3D Printing All-Aromatic Polyimides using Mask-Projection Stereolithography: Processing the Nonprocessable
Christopher B. Williams, Timothy E. Long, Danesh Tafti, Maruti Hegde, Susheel Sekhar, Viswanath Meenakshisundaram, Nicholas Chartrain
High-performance, all-aromatic, insoluble, engineering thermoplastic polyimides, such as pyromellitic dianhydride and 4,4′-oxydianiline (PMDA–ODA) (Kapton), exhibit exceptional thermal stability (up to ≈600 °C) and mechanical properties (Young's modulus exceeding 2 GPa). However, their thermal resistance, which is a consequence of the all-aromatic molecular structure, prohibits processing using conventional techniques. Previous reports describe an energy-intensive sintering technique as an alternative technique for processing polyimides with limited resolution and part fidelity. This study demonstrates the unprecedented 3D printing of PMDA–ODA using mask-projection stereolithography, and the preparation of high-resolution 3D structures without sacrificing bulk material properties. Synthesis of a soluble precursor polymer containing photo-crosslinkable acrylate groups enables light-induced, chemical crosslinking for spatial control in the gel state. Postprinting thermal treatment transforms the crosslinked precursor polymer to PMDA–ODA. The dimensional shrinkage is isotropic, and postprocessing preserves geometric integrity. Furthermore, large-area mask-projection scanning stereolithography demonstrates the scalability of 3D structures. These unique high-performance 3D structures offer potential in fields ranging from water filtration and gas separation to automotive and aerospace technologies. High-performance, thermoplastic, fully aromatic polyimide structures are 3D printed for the first time using mask-projection stereolithography (MPSL). Synthesis of soluble, photo-crosslinkable polyamic diacrylate ester enables MPSL upon dissolution in a solvent. The 3D organogels with micrometer-scale resolution undergo conversion to a 3D polyimide on thermal imidization without loss in part fidelity. Mechanically robust, high-performance, fully aromatic 3D polyimide is obtained.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/adma.201701240

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