Nov 21, 2017 | By David

Researchers in China recently made a breakthrough that shows significant promise for the future of stereolithography and digital light processing technology. These two 3D printing techniques make use of special inks that harden with exposure to light, and they are capable of producing objects with good structure and material properties when compared to the more basic FDM 3D printing. The main limiting factor to this is the quality of the ink itself, as this determines the quality of the finished 3D printed object. A new solvent-free, photo-curable polyimide ink has now been developed that performed better in tests than many other materials currently used.

The researchers at the Lanzhou Institute of Chemical Physics (LICP) at the Chinese Academy of Sciences wanted to fabricate a new material that would expand the possibilities of light-based 3D printing beyond the production of ornamental items or prototypes. The team, consisting of Yuxiong Guo, Zhongying Ji, Yun Zhang, Xiaolong Wang and Feng Zhou, received support from the China West Light Foundation of Academy of Sciences, the LICP Special Recruitment Project, the Natural Science Foundation of Gansu Province and Gansu Puruite Technology Co., Ltd. The results of their project, which proved to be a great success, have now been published in the Journal of Materials Science.

Existing materials most commonly used for SLA or DLP technology tend to be epoxy resins or acrylic esters. While these are capable of producing intricate geometries and relatively sturdy structures, tougher conditions tend to expose their weaknesses rapidly, so objects produced with this kind of 3D printing are generally limited in terms of their functionality. The new ink will enable the production of much more resilient structures in terms of heat resistance, and it is also highly soluble, which is another key property for 3D printing inks as it reduces the need for additional solvents which will affect the final print quality.

The published paper, "Solvent Free and Photocurable Polyimide Inks for 3D Printing", has some details about the chemical process that produced this exciting new 3D printing material. It says that "Maleic anhydride-terminated polyimide oligomers with a glycidyl methacrylate graft were prepared by one-step imidization of phenolic hydroxyl groups containing diamine and aromatic dianhydride in high boiling-point solvent, followed by the reaction of glycidyl methacrylate with the phenolic hydroxyl groups. The good solubility of the oligomers in reactive diluents allowed the formation of a solvent-free photocurable ink." Once this was complete, the ink was used in a DLP 3D printer to produce a range of different objects.

3D printing with the ink was successful, producing complex geometries and intricate structures without much difficulty. Testing of the material properties of the 3D printed objects was the next step. The objects were cured in a conditioning oven at a temperature of 300 degrees Celsius, as well as being immersed in hot oil of varying viscosities, to see how they would cope with the intense heat. The researchers then measured hardness, tensile strength and elongation- all of which are crucial mechanical properties for an object to be used in high-performance manufacturing. Chemical inertness was also tested, as this shows the ability of a material to cope with exposure to various chemicals, which could be a regular occurrence for certain industrial applications.

The objects produced with the new photo-curable polyimide ink passed all these tests with flying colors, showing great promise for the future of SLA and DLP 3D printing technology. According to the researchers, the ink would be ideal for "constructing parts and models, such as micro-oil filters, through-tubing materials, cooling valves, and various engine components’’. The electronics sector, aerospace aviation, and the automotive industry are just a few of the fields that may soon be benefitting from one of the most advanced 3D printing inks yet developed.



Posted in 3D Printing Materials



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