Generally, there are 3 classes of TPEs that are processed into filaments.
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TPE-S = Filament made of SEBS, i.e., styrene-ethylene-butadiene-styrene. Adhesion to PP and PE is possible. TPE-S filaments are rarely offered and have a hardness range of approximately 70 Shore A to 60 Shore D.
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TPEE = Thermoplastic copolyester elastomers, also called TPC, adhere to ABS, PET-G, PLA, TPU. High resilience, not UV-stable in color. Hardness range approx. 30–55 Shore D.
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TPU = Thermoplastic polyurethane. These are the most commonly offered materials and have a hardness range of 65 Shore A to 60 Shore D.
We distinguish three of the most important TPU classes.
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Ester TPU = Most commonly offered, relatively inexpensive. High chemical resistance, high resilience. Susceptible to hydrolysis (mechanical properties are slowly lost in high humidity/temperature), not UV-stable in color. Frequently used for shoe soles.
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Ether TPU = Higher quality than ester TPU, microbe-resistant, hydrolysis-resistant, high chemical resistance, but not UV-stable in color. Frequently used in automobiles due to its long lifespan. Usually black, it is not prone to UV yellowing.
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Aliphatic TPU is very expensive; its main advantage is UV resistance, even in light colors. Otherwise, it's similar to ether TPU. Aliphatic TPU is used, for example, for flexible, transparent rear windows in convertible roofs. It's very rarely offered as a filament.
Working with TPU in 3D printing
TPU is often negatively reviewed when it comes to its suitability for 3D printing. This is due, on the one hand, to the quality of the polymer itself, the quality of the filament, and on the other hand, to the 3D printers, which are often not suitable for flexible materials.
Only TPUs with a specific stiffness and hardness can be used with Bowden printers. We recommend TPUs with a Shore A to Shore D rating of 98.
Direct-drive systems are better suited. These printers can sometimes print TPU up to approximately 60 Shore A (extremely soft).
Soft TPU types may need to be printed at a slower speed. This is generally possible at 20-40 mm/sec. Adhesion to the print bed can be extremely good, and warping is unlikely. The harder the TPU type, the lower the adhesion to the print bed and the greater the risk of warping. From 98 Shore A up to 60 Shore D, we recommend using a heated print bed and covering it with blue tape for better adhesion and reduced warping.
A blower fan is generally helpful for quickly cooling the printed TPU.
TPU is mechanically very stable, does not break, and is highly cut- and abrasion-resistant. Furthermore, TPU has the property of adhering very strongly to other hard plastics, which is helpful for two-component objects. Suitable bonding partners for TPU are primarily ABS, ASA, PC, PLA, and PETG.