In situ 3D printing of poly-ether-ether-ketone / poly-ether-imide hierarchical cellular foams containing electromagnetic absorbent

For the expanding application of light-weight integral structures meeting both structural and physical requirements, the development of advanced materials with high performances in multiple functions and their automatically manufacturing processes with mass production potential at low cost has received sustained attention from both academia and industry. Therefore, an in situ 3D printing technology of poly-ether-ether-ketone (PEEK)/ poly-ether-imide (PEI) hierarchical cellular foam containing electromagnetic absorbent was proposed in this paper. Fillers with electromagnetic functions, nano-carbon and Fe₃O₄, were introduced into the blend of two high-performance thermoplastics, semicrystalline PEEK and amorphous PEI, and a lightweight nanocomposite foam with functionalized hierarchical cellular structure in micrometer scale was manufactured by combining in situ foaming process into 3D printing. The in situ foaming mechanism of the materials was carefully studied and optimal process parameters were obtained. When the desorption time of materials is 48 h, the 3D printed foams present the smallest cell size and the highest cell density. The foaming behavior of this special material is different from that of batch foaming. Mechanical tests show that the flexural modulus increases with decreasing cell size and increasing cell density. In X-band (8.2–12.4 GHz), the hierarchical cellular structure with gradient layers performs low reflectivity and absorption-dominant EMI shielding properties. The lightweight nanocomposite foam manufactured by the in situ 3D printing technology have great potential for applications such as functional-structural integrated skins in aerospace, protection of high-power instruments and 5 G communication products.