3D printing of heat-resistant thermosetting polyimide composite with high dimensional accuracy and mechanical property

Abstract

3D printing of polyimide parts with high heat resistance, dimensional accuracy and mechanical property is quite challenging because the manufacturing requirements restrict molecular structural design. Hence, combination of molecular design of thermosetting polyimide oligomer and a two-step reactive 3D printing strategy is conducted. Siloxane-containing phenylethynyl-terminated polyimide oligomer powders with milled carbon fibers are developed, which can be precured with laser scanning in a selective laser sintering (SLS) equipment, forming self-standing green parts with complex geometries. These green parts can be thermally postcured to polyimide parts with high dimensional stability. The linear shrinkage in Z axis is less than 4.74 %. Oligomers experience crosslinking of phenylethynyl groups and oxidation crosslinking of siloxane units during SLS and postcuring. Therefore, the printed polyimide parts give a tensile strength of 82 MPa and a glass transition temperature of 419 °C. Honeycombs fabricated by this strategy give higher specific compression strength and can withstand temperature as high as 400 °C. The wear-resistant self-lubricating materials prepared by this approach exhibit a reliable tribological property after atomic oxygen and ultraviolet irradiations. These findings will provide useful insight for designing and fabricating structural components with complex shapes that might be applied in aerospace extreme environment.