4D Printing of PEEK ‐ PEI Based Composites via Indirect Microwave Activation

ABSTRACT This study investigates the development of a 4D‐printable composite based on polyether ether ketone (PEEK), polyetherimide (PEI), and carbonyl iron particles, combining the high thermal and mechanical performance of PEEK/PEI matrices with the microwave‐responsive heating capability of carbonyl iron. The composite was designed for microwave‐induced thermal activation, in which the applied microwave field is converted into localized heat by the carbonyl iron particles, enabling remote triggering of the shape‐memory effect (indirect activation). Three formulations containing 40%, 50%, and 60% by weight of carbonyl iron were successfully fabricated and characterized. Shape memory behavior was evaluated through both direct thermal and indirect microwave activation. The composite PEEK‐PEI‐50Fe was the only composite that exhibited good printability coupled with shape memory properties under microwave irradiation with effective shape fixity (88.58%) and recovery (87.77%), with recovery time (≈90 s), enabled by localized heating generated by the carbonyl iron particles, allowing for the reaching of switching temperature (≈200°C). The produced composite shows also high thermal stability (> 500°C) and significant mechanical reinforcement compared to neat reference due to the presence of iron particles ( E ↑ 587%, σ ↑ 65%, ε ↓ 76.7%), highlighting the strong potential of this composite for advanced applications in extreme environments.