TPU

TPU (thermoplastic polyurethane) is a thermoplastic elastomer: in service it behaves much like rubber, yet it can be remelted and processed like an ordinary thermoplastic. Its chains consist of hard segments (a diisocyanate with a short-chain diol) and soft segments (a polyester or polyether polyol). The hard segments form physical crosslinks that release on heating, so unlike rubber, TPU needs no vulcanization.

Depending on the segment ratio, TPU hardness ranges from about 60 Shore A, comparable to soft rubber, up to grades measured on the Shore D scale that are stiff and only slightly flexible. 3D printing most often uses 85A to 98A. Elongation at break is typically several hundred percent. The main strength of TPU is very high resistance to abrasion and tear propagation, where it outperforms most rubbers, plus good resistance to oils, greases and fuels and flexibility even below freezing. Continuous service is usually limited to about 80 °C.

Polyester-based TPU offers better mechanical properties and resistance to abrasion and oils, but it hydrolyzes in warm, humid environments. Polyether-based TPU resists hydrolysis and microbes better and stays flexible at low temperatures, so it is chosen for parts in water and outdoors. Aromatic grades yellow under light; aliphatic grades are lightfast and used for clear films and cosmetic parts.

TPU is processed by injection molding, extrusion (hoses, films, cable jackets, belts) and two-shot molding, where the soft layer is molded directly onto a rigid PC or ABS part (soft-touch grips, integrated seals). In 3D printing it is used in FDM (nozzle usually 210 to 240 °C, slow printing and an extruder with a short filament path, ideally direct drive) and in the powder processes SLS and MJF, which can print soft lattice structures with tuned stiffness. Soft grades machine poorly, but harder polyurethanes are turned into parts such as hydraulic seals, and flat parts are waterjet cut or die cut from sheet.

Choose TPU for parts that need to flex, absorb shocks and vibration or resist abrasion: feet and bumpers, damping pads, protective covers and sleeves, bellows, casters and rollers, belts, hoses, cable jackets, shoe soles, handles and gripper pads.

In product development, 3D printed TPU is a fast route to prototypes of rubber parts without making a mold. For appearance parts and small batches with a precisely specified hardness, vacuum casting of polyurethane resins in silicone molds is an option; for large volumes, injection molding.

TPU is not a universal substitute for rubber. Under sustained compression, especially at elevated temperature, it shows a higher compression set than vulcanized rubbers such as EPDM or NBR, so a static TPU seal can lose sealing force over time. For sustained high temperatures, hot water or steam, choose another elastomer, such as EPDM or silicone, depending on the environment.

Shore hardness alone does not determine part stiffness. In a 3D printed part, wall thickness, infill and geometry matter greatly, so verify function on a sample. Soft filaments below 85A are difficult and slow to print. TPU absorbs moisture; dry it before printing or molding. In your RFQ, state the hardness, the type (polyester or polyether) and the operating environment.