3D-Printed Shoe Uppers: How to Choose the Right Materials and What about Performance?
Fu Ranqian's team at Xi'an Polytechnic University conducted research on material selection and performance optimization for 3D-printed shoe uppers, focusing on three core materials: thermoplastic polyurethane (TPU), flexible polylactic acid (PLA), and polyvinyl alcohol (PVA). They used fused deposition modeling (FDM) technology to fabricate the upper's structural components and combined multi-dimensional testing to analyze their applicability, providing a scientific basis for the application of these materials in 3D-printed shoe uppers.
The research clarified the functional roles of the three materials: TPU and flexible PLA were selected as candidate materials for the main fabric of 3D-printed shoe uppers, while PVA served as a support material. To verify the material's performance, the team used scanning electron microscopy, infrared spectroscopy, X-ray diffraction, differential thermal analysis, and mechanical testing to systematically evaluate the structural and performance changes of the materials before and after 3D printing.
In terms of micromorphology and structural stability, scanning electron microscopy (SEM) observations revealed a significant reduction in surface roughness of TPU and flexible PLA after melt spinning (a key step in 3D printing). While TPU exhibited pronounced surface pits before spinning, these pits largely disappeared afterward; while flexible PLA retained only a few tiny pits. Both surfaces remained smooth, meeting the surface flatness requirements for upper fabrics. Infrared spectroscopy and X-ray diffraction tests revealed that the high-temperature melt spinning process did not alter the molecular structures of TPU and flexible PLA, with only slight changes in the intensity of the characteristic absorption and diffraction peaks, demonstrating that the core properties of the materials were preserved during the printing process.
Heat resistance tests revealed the thermal stability characteristics of the three materials: TPU begins to decompose slightly at around 80°C, with a melting temperature of approximately 220°C; flexible PLA begins to decompose slightly at around 50°C, with a melting temperature of approximately 180°C; and PVA begins to decompose slightly at around 75°C, with a melting temperature of approximately 200°C. The thermal decomposition and melting temperature ranges of all three materials are well within the printing parameter range of FDM technology, ensuring stability during the printing process.
Mechanical performance testing further clarified the application advantages of the main material: the TPU filaments demonstrated a breaking strength of 310.21 cN and a tensile strength of 613.42 MPa, demonstrating excellent tensile strength and suitability for shoe uppers requiring high mechanical strength. The flexible PLA filaments achieved an elongation at break of 720.28%, demonstrating excellent flexibility and enhancing the fit between the shoe upper and the foot. Elastic recovery testing revealed that the elastic recovery rates of TPU at a constant elongation and constant load were 71.23% and 75.35%, respectively, while those of flexible PLA were 42.86% and 46.38%. Both meet the elasticity requirements of the shoe upper during use, preventing deformation and difficulty in recovery.
Performance testing of the support material PVA focused on its solubility. It exhibits excellent water solubility at room temperature. The colloidal solution formed upon dissolution does not affect the surface quality of the shoe upper model and is easily removable after printing. It is suitable for forming complex hollow structures in 3D printed shoe uppers, while also being non-toxic and biodegradable.
In summary, the study confirmed that TPU and flexible PLA meet the requirements of 3D printed shoe upper main fabrics in terms of structural stability, heat resistance and mechanical properties, while PVA is suitable as a supporting material; the coordinated use of the three can effectively guarantee the molding quality and performance of 3D printed shoe uppers, providing a key reference for the material application of 3D printing shoemaking technology.
