Research on Improving the Mechanical Properties of 3D Printing TPU Materials
The mechanical properties of materials refer to the mechanical characteristics of materials when they are subjected to various external loads in different environments, including hardness, brittleness, strength, plasticity, rigidity, etc. In the process of 3D printing TPU materials, various mechanical indicators of the sample are important factors affecting product quality. In order to explore the tensile properties of 3D printed TPU materials, we used FDM 3D printing technology to prepare samples of two different materials, polylactic acid (PLA) and TPU, by lamination, and continuously changed the volume fraction of TPU during the preparation process. and material layout, the tensile behavior of PLA/TPU samples of different materials was investigated. The results show that the volume fraction of TPU has a significant effect on the tensile strength and elastic modulus of PLA/TPU samples, and the content of PLA components plays a leading role in the tensile strength of PLA/TPU composites. In the case of the same volume fraction of PLA TPU.
The 3D printing PLA/TPU material with pure TPU as the surface material has the highest yield stress and elastic modulus. We conducted research on the effect of TPU hard segment content on the rheological properties of PLA/TPU blends. The study uses a twin-screw extruder to mix amorphous polylactic acid (PLA) and semi-crystalline polylactic acid (scPLA) with three different hardness TPUs at the same mass fraction at processing temperatures of 150 °C and 190 °C. , to obtain a PLA/TPU blend.
Afterward, the microscopic morphology of the samples was observed through various characterization methods, and the thermodynamic properties, tensile properties, and rheological properties of the samples were tested. The results show that the use of TPU with low hardness is more beneficial to enhance the ductility and impact resistance of the blend, while the increase of TPU hard segment content significantly improves the compatibility between PLA and TPU phases. After the TPU hard segment content increases, most of its crystalline structure will be melted, thereby forming a finer TPU dispersed phase and a blended system with a more uniform structure.
Research on Improving Other Properties of 3D Printing TPU Materials
In addition to heat resistance and mechanical properties, in recent years, researchers have also conducted in-depth research on the improvement of other physical and chemical properties of 3D printing TPU materials. Thermal conductivity is an important index to evaluate the thermodynamic properties of materials. In the process of 3D printing TPU materials, in order to improve the thermal conductivity of TPU products
In a study, we used FDM to prepare TPU composites filled with high thermal conductivity hexagonal boron nitride (hBN) lamellae, studied the components and related properties of the composites, and explored the nozzle diameter, The impact of 3D printing parameters such as printing speed and filler loading on product quality
Impact. Finally, the research team successfully prepared a high thermal conductivity hBN/TPU composite material with shear-induced alignment. The resulting hBN/TPU composite maintains the anisotropic properties of the hBN filler. When the filler filling amount is 40%, the in-plane thermal conductivity of the sample filled along the printing direction is 2.56W·m-1·K-1 at 100°C, which is the thermal conductivity of the sample filled along the thickness direction under the same filler load. 2.8 times, and more than 10 times the thermal conductivity of pure TPU samples prepared under the same conditions. In addition, the study also shows that the highly thermally conductive hBN/TPU composites prepared by FDM 3D printing have excellent electrical insulation and dielectric properties, suggesting that 3D printing is an effective method to obtain composites with excellent properties. Intrinsic self-healing polymers (SHPs) are man-made polymers that extend the life of products by repairing damage, such as cracks or scratches, autonomously or on demand. In recent years, due to the simple healing conditions of TPU materials (healing at room temperature) and good mechanical properties, it has also attracted widespread attention in the field of self-healing polymers. In order to explore the self-healing properties of TPU, Ritzen et al. developed a 3D printing method based on the FDM method and tested the mechanical properties of low-temperature self-healing thermoplastic polyurethane (SH-TPU) samples manufactured by this method. The study found that compared with commercial 3D printed polyurethane, although the mechanical properties of 3D printed SH-TPU are slightly lower than commercial polymer products, the printed part has a complete shape and good self-healing ability, which has high research value.
Pic1 Thermally activated shape memory recovery process of pure PCL and PCL/TPU composites with different compositions
The shape memory effect refers to the phenomenon that after a solid material undergoes a certain plastic deformation under certain conditions and is heated to a certain temperature, the material completely returns to the original shape before deformation. TPU is a representative thermally stimulated shape memory polymer (SMP), which has been widely used in SMP research in the past few decades. Of all the fabrication methods, only 3D printing is capable of cost-effectively producing custom complex structures. Therefore, it is a promising research direction to use the 3D printing method to study the shape memory effect of TPU. We studied the shape memory effect of PCL/TPU blends with different components based on FDM technology. It was found that the FDM printing process did not affect the shape memory effect of the PCL/TPU blend. Among the PCL/TPU blends, the PCL7/TPU3 composite has the best shape memory performance. Huang et al. [18] prepared PLA/TPU and multi-walled carbon nanotubes (MWCNTs) blends by extrusion method and conducted in-depth studies on their thermally induced shape memory effect and mechanical properties. The results show that when the ratio of PLA/TPU is 70/30, TPU can form a continuous phase in PLA, and the added CNTs can be selectively adsorbed in TPU, which significantly improves the shape memory efficiency of solid composites, making the final obtained corrugated PLA/TPU/CNT nanocomposites have good mechanical properties. This is a new type of structural shape memory system, which is of great significance in industrial production and applications. In addition to the above properties, the research on the modification of TPU materials also includes aging resistance, flame resistance, biocompatibility, and other aspects. In short, TPU material has good processing and modification performance, and its performance can be improved through different modification methods.
Application of 3D printing TPU material
TPU material has both the high elasticity of rubber and the rigidity of plastic. It can be melt-processed and is suitable for high-precision and high-resolution printing; its hardness range is wide and its mechanical properties are easy to control. It also has certain wear resistance and oil resistance. , aging resistance, combined with 3D printing technology, can produce complex porous structures that are difficult to manufacture by traditional techniques. Therefore, TPU materials made by 3D printing technology, especially TPU filamentary wires processed by FDM technology, have been widely used in the field of design, shoe materials, clothing, biomedical, automotive, film and television animation, etc.
Application of 3D printing TPU materials in the field of shoe materials
TPU has excellent elasticity, abrasion resistance, tear resistance, and bending properties, meeting the requirements of the shoe material industry. Therefore, TPU materials are widely used in sports shoes air cushions, golf shoes, skates, and other fields. The elongation at the break of the TPU material is very high. Using the characteristics of the material, the manufacturer can manufacture a shoe material with good fatigue resistance. After the production is combined with the 3D printing process, the cost of the mold can be removed and the manufacturing time can be effectively saved. In a previous study, Nike of the United States and Prodways, a French 3D printing company, are cooperating to use TPU materials for the 3D printing of shoes. This technology can be used to produce outsoles, midsoles, and insoles of shoes. Its elongation at break can exceed 300%, and its performance is excellent, which can meet the needs of customers' personalized customization.
Application of 3D printing TPU materials in the field of clothing
The TPU material itself is non-toxic and harmless, so it can directly contact the skin. It is an ideal material for clothing 3D printing. Compared with traditional clothing materials, the advantage of 3D printing materials is that their dynamic surface materials can be customized, and it is easy to control design parameters such as pore size, volume, shape, etc., so as to design all kinds of clothing with a good sense of fit. 3D printing can obtain complex structures, which can enrich the designer's design ideas and make the produced clothing more personalized. Therefore, although 3D printing technology started late in the field of clothing, it has developed rapidly. In order to solve the problem of friction and compatibility of 3D printing plastics on complex human skin, Kasar et al. chose TPU and polyamide (TPA) two low-friction 3D printing materials in a study, respectively in wet and dry conditions. Next, the friction test was carried out on TPU/TPA and skin model. In addition, TPA and TPU can obtain low coefficient of friction (COF) values under both wet and dry conditions by reducing surface roughness, which can effectively reduce adhesive friction with the skin, and are good plastics for 3D printing of clothing. We studied the application of flexible TPU materials in detachable women's clothing. Taking sustainable fashion as the starting point, this research uses flexible TPU-based 3D printing technology to create the effect of bionic plant leaf veins and flower meridians and mixes and matches materials with special texture effects formed by 3D printing to enhance the layering of clothing.
Pic2 3D printing physical three-dimensional modeling based on flexible TPU
Application of 3D printing TPU materials in the automotive field
3D printing can manufacture parts urgently needed by automobile companies, quickly carry out personalized manufacturing and parameter correction of products while saving manufacturing costs, and solve practical application problems. Therefore, 3D printing TPU materials have been widely used in the automotive field. We conducted research on TPU materials for 3D printing of non-pneumatic tires based on FDM technology. The results show that the wear resistance of TPU material is significantly better than natural rubber, butadiene rubber, and styrene-butadiene rubber. In addition, the research team also successfully manufactured non-pneumatic tires using FDM technology in combination with the 3D printing process of TPU materials. Beijing University of Chemical Technology and Shandong Linglong Tire Co., Ltd. jointly developed a polyurethane tire that meets standard specifications prepared by 3D printing technology. The tire is made of TPU material and printed through the FDM process. It is a non-pneumatic tire and is expected to be widely used in the tire field.
(a) Non-pneumatic tire with rim structure (b) Performance test diagram of non-pneumatic tire
Application of 3D printing TPU materials in the field of biomedicine
3D printing is progressing rapidly in the medical field. At present, it can realize the printing of some organs of the human body, which has important research significance. Due to its excellent mechanical properties and good biocompatibility, TPU materials are widely used in long-term implanted medical devices and artificial organs. In the field of biomaterials, 3D printing TPU materials are mainly used for tissue engineering scaffolds. Chen et al. explored the FDM 3D printing technology of TPU/PLA/graphene oxide (GO) nanocomposite and its application prospect as a biocompatible material. In this study, ultra-thin slices of TPU/PLA blends containing different mass fractions of GO were prepared, and NIH3T3 mouse embryonic fibroblasts were used for cell viability/cytotoxicity staining experiments. The results showed that the composite material has good biocompatibility with NIH3T3 cells and is a good candidate material for tissue engineering scaffolds.
Application of 3D printing TPU materials in other fields
In addition to the above fields, 3D printing TPU materials are also widely used in many other fields. In the field of construction, using TPU materials and 3D printing technology, it can be printed to form high-strength, high-rigidity, and complex-structure building materials, which have good comprehensive economic benefits. In the field of aerospace, TPU wire can be used to manufacture high-precision parts, combined with FDM technology, it can speed up the research and development process of advanced materials. In the field of film and television animation, TPU material is often used for 3D printing various character models due to its good flexibility and durability. In the field of education, TPU materials can also be used for 3D printing of teaching tools and models, making the classroom teaching process more vivid.
