Preparation And Performance Research Of Self-healing TPU Materials For 3D Printing

Additive manufacturing（AM）has become a basic process and has led to the new industrial revolution in various fields.Melt deposition technology（FDM）has the advantages of low price and simple operation in 3D printing technology.However,when printing complex models,FDM needs to add support structure and weak interlayer bonding force,which limits its application field.In this paper,self-healing polyurethane was designed and synthesized,and 3D printed components were assembled into a model with complex structure by FDM technology.The self-healing properties of materials were utilized to repair internal gaps between product filaments,enhance adhesion between layers,and improve the mechanical properties of products.Moreover,objects with complex structures are decomposed into simple structures that are easy to print,effectively reducing support structures while improving printing efficiency.We used DSC,TGA,XRD and other methods to characterize the synthetic polyurethanes with different repair mechanisms.It was found that with the increase of hard segment,the strength of the self-healing polyurethanes with increased B-N coordination bonds and hydrogen bond aggregation of hard segment was significantly improved.B-N coordination self-healing polyurethane PU-BN₃has excellent mechanical strength（4.5 MPa）,which can still retain more than 87%of the mechanical strength after repeated processing.The glass transition temperature is 7.8℃,and the three synergistic effects of hydrolyzation-esterification of borate ester,B-N coordination bond and hydrogen bond aggregation realize self-healing,which has excellent self-healing property at room temperature.After 24 h of repair,the tensile strength reached 3.7 MPa,and the repair efficiency was over 80%.With the increase of ionic bond,the crosslinking density increases and the material changes from soft material to hard material.The crosslinking network restricts the movement of polymer chain,increases the Tg,orderly stacking of hard segment and decreases the elongation at break.The non-covalent crosslinking of polyurethane with tertiary amino group by polyacid is simple and effective,and the mechanical properties of self-healing polyurethane elastomers can be adjusted by the amount and type of acid.The tensile strength of ion-self-healing polyurethane PU-TPA is 12.9 MPa,43 times that of pure polyurethane,and the elongation at break is 520%.The above self-healing polyurethane materials realize self-healing through the synergistic effect of multiple bonds,and the introduction of reversible bonds enhances the mechanical properties of the materials.Finally,PU-BN3 and PU-CA were used to prepare printing consumables,and FDM technology was used to print complex model components.After assembling the model,it was solid and reliable as a whole.