3D printed sequence-controlled copolyimides with high thermal and mechanical performance

Inadequate heat resistance and mechanical property limited the application of 3D printed polymer parts in aerospace industry. To address this restriction, a kind of sequence-controlled copolyimides with both amorphous segment and crystalline segment, suitable for fused deposition modeling 3D printing technique were designed and synthesized. The effect of content and distribution of crystalline segment on melt fluidity and crystallization behavior was disclosed. It was found that copolyimide with crystalline segment only distributed in the end of backbone exhibited good melt fluidity and slow crystallization rate. Microstructure change of the corresponding copolyimide during 3D printing and thermal annealing was revealed. Due to slow crystallization rate of copolyimide, no crystals formed during 3D printing. Thus, the diffusion and entanglement of polymer chain at interface were guaranteed. Thermal annealing at 350 °C facilitated diffusion and arrangement of polymer chain, leading to the enhancement of interfacial bonding and crystallization of copolyimide at interface and in filament. Therefore, the printed copolyimide specimens exhibited high heat resistance, high mechanical property and excellent interfacial bonding performance. The tensile strength of specimens printed in XY plane with 0° infill direction (XY-0), XY plane with 90° infill direction (XY-90) and XZ plane with 90° infill direction (XZ-90) were 110 MPa, 96 MPa and 57 MPa, respectively. The tensile strength of XY-0 printed specimen at 200 °C was 186 % higher than that of XY-0 printed amorphous polyimide specimen, reaching 40 MPa. This study expanded the kinds of polymeric materials suitable for fused deposition modeling, and provided the possibility of printing high performance engineering parts.