A comprehensive review published on ScienceDirect by researchers from the RMIT Centre for Additive Manufacturing in Melbourne and India’s CSIR-National Chemical Laboratory (CSIR-NCL) outlines current progress in additive manufacturing (AM) of polyimides (PIs). The study, co-authored with the Academy of Scientific and Innovative Research (AcSIR) in Ghaziabad, examines how polymer chemistry and processing strategies are enabling the 3D printing of high-performance PIs previously considered unprocessable due to insolubility, infusibility, and narrow temperature ranges.
Polyimides are valued for their thermal stability, chemical resistance, and mechanical strength, but their processing remains challenging. Conventional fabrication relies on soluble poly(amic acid) precursors that are later imidized at high temperatures, while thermoplastic PIs (TPIs) demand precise control of viscosity and thermal windows. The review identifies vat photopolymerization (VPP), material extrusion (MEX), direct ink writing (DIW), and material jetting (MJ) as the main AM pathways used to adapt PIs for complex structures, high-temperature components, and multifunctional devices.
VPP was the first AM route demonstrated for polyimides. Two independent studies published on March 3, 2017, reported the 3D printing of PIs using digital light processing (DLP) and mask-projection stereolithography (MPSL). Guo et al. developed a solvent-free, photocurable polyimide oligomer synthesized from 6FDA and 6FOHA monomers with glycidyl methacrylate modification. The resulting methacrylate-functionalized resin enabled ultraviolet curing and high-resolution printing without solvent removal. Printed micro-oil filters exhibited strong mechanical and thermal properties suitable for high-temperature applications.
In parallel, another study achieved the first MPSL printing of PMDA-ODA polyimide, commercially known as Kapton™, using poly(amic ester) precursors with pendant acrylate groups. After printing, solvent removal and thermal imidization at 350 °C yielded fully imidized structures with 52 % isotropic shrinkage. Subsequent work by Arrington et al. pyrolyzed the same organogel structures at 1000 °C to form dense, monolithic carbon components that retained their geometry with approximately 55 % linear shrinkage. Further developments include photocurable PI/PTFE composites for self-lubricating bearings, shape-memory PI inks for 4D printing, and hybrid VPP-DIW processes for high-viscosity resins.
Material extrusion using thermoplastic polyimides
Extrusion-based 3D printing, including fused filament fabrication (FFF) and direct ink extrusion, has focused primarily on thermoplastic PIs such as ULTEM™ 9085, ULTEM™ 1010, and EXTEM™ VH1003. These polyetherimide and polyimide blends combine processability with thermal strength suitable for aerospace components. Studies summarized in the review show that build orientation strongly influences mechanical performance. Specimens printed in the ZX orientation exhibit reduced tensile and flexural strength due to weak interlayer bonding, while horizontally printed parts show higher compressive strength. Optimal nozzle temperatures between 320 °C and 340 °C balance interlayer adhesion and viscosity; overheating causes foaming and delamination, whereas lower temperatures result in incomplete flow.
Continuous fiber reinforcement further improves performance. Ye et al. demonstrated separated continuous carbon-fiber reinforced TPI composites with tensile and bending strength increases of 214 % and 167 % compared to pure TPI. Additional research optimized nozzle diameter, drying time, and cooling conditions to reduce porosity and improve bonding. ULTEM-based studies examined the influence of raster pattern, infill density, and post-printing annealing on strength and fatigue life. Fiber-reinforced variants such as carbon-fiber-wrapped ULTEM™ 9085 and CF-filled ULTEM™ 1010 showed improved stiffness, while temperature exposure and environmental aging affected durability. Together, these findings establish parameter windows for printing high-temperature engineering polymers with reproducible mechanical properties.
Direct ink writing and UV-assisted curing
DIW has become a flexible platform for processing polyimide pastes and precursor inks. Using shear-thinning formulations, DIW enables complex geometries while preserving dimensional accuracy after curing. PI/silica composite aerogels printed through DIW and thermally imidized show thermal stability between -50 °C and 1300 °C, low thermal conductivity, and high flame resistance. Solvent-free photocurable comb poly(amic acid) inks containing glycidyl methacrylate groups achieve less than 6 % shrinkage and glass-transition temperatures around 204 °C.
Aqueous PAA salt hydrogels provide an environmentally safer route for DIW by enabling sol-gel transitions in water. UV-assisted DIW (UV-DIW) using hydroxyethyl methacrylate-modified PAA precursors produces polyimide structures with high modulus and low shrinkage after staged imidization. Additional studies developed gradient conductive MXene/CNT/PI aerogels for electromagnetic interference shielding with efficiencies up to 68 dB and freeze-casting assisted DIW for honeycomb PI aerogels with sound absorption coefficients peaking at 0.86. Other DIW work includes tribology-enhanced PI/MoS₂ composites, thermosetting SiO₂-filled PIs for aerospace structures, and solvent-free polyamide-imide scaffolds for high-temperature components.
Material jetting and composite reinforcement
Material jetting has been explored through bismaleimide (BMI) precursors and multijet fusion (MJF) of PI-fiber composites. BMI oligomers with molecular weights between 689 and 5000 g/mol polymerize via photo-induced cyclodimerization, allowing rapid UV curing into crosslinked thermoset PIs with high heat resistance. MJF studies incorporating short chopped PI fibers into a PA12 matrix demonstrated 43 % higher tensile strength and 46 % higher flexural strength compared to neat PA12. Thermogravimetric and differential scanning calorimetry analysis confirmed enhanced decomposition temperature and crystallinity. Fiber alignment along the print direction created anisotropic reinforcement, while annealing improved strength but increased brittleness due to higher crystallinity. Fiber contents exceeding 10 wt % reduced printability by introducing porosity.
The RMIT and CSIR-NCL authors identify remaining obstacles to scalable AM of polyimides. High processing temperatures above 350 °C demand specialized hardware, while elevated melt viscosity limits flow in extrusion systems. Hygroscopic behavior requires controlled drying to prevent voids, and post-processing imidization introduces shrinkage and internal stress. Rheological optimization, improved bed adhesion, and temperature-controlled chambers are recommended to mitigate warping. Sustainability is another concern: the study highlights the need for recyclable TPI systems and solvent-free or deconstructable chemistries that maintain performance without compromising stability.
According to the review, future research will focus on molecular tailoring for functionalization, 4D printing of shape-memory PIs, and integration of PIs with metals or ceramics for hybrid structures. AI-driven materials design and process optimization are also expected to accelerate formulation discovery. The authors conclude that combining chemical design with high-temperature printer technology could position polyimides as viable alternatives to metals in aerospace, electronics, and energy applications, transforming high-performance polymer manufacturing through additive techniques.
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Featured image shows (a) Synthesis of photosensitive PI oligomer PI-g-GMA and (b) step-by-step procedure for DLP 3D printing of PI ink. Image via Royal Society of Chemistry.
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