What is Thermoplastic Polyurethane (TPU)?

Thermoplastic polyurethane (TPU) belongs to a class of polyurethane plastics having many important properties such as elasticity, transparency, and resistance to grease, oil, and abrasion. It is unique due to its extremely flexible nature. Technically speaking, TPUs are made up of thermoplastic elastomers. However, it is better to separate them from acids, solvents, and fuels, which can affect their properties.

Commercially available TPUs are of different types depending on the application;

1. Polyester-based TPUs, which are derived from adipic acid esters,
2. Polyether-based TPUs, which are derived from tetrahydrofuran ethers,
3. Polycaprolactone-based TPUs, which are derived from thermoplastic polyurethane elastomer.

Polyether-based TPUs are commonly used in wet environments, and polyester-based TPUs are commonly used to resist oil and hydrocarbon. A smaller class of polycaprolactone-based TPUs can perform optimally at low-temperature and are comparatively more resistant to hydrolysis.

Advantages of TPU Flexible Filament

TPU has different advantages such as resistance to abrasion, ability to perform at low temperature, elasticity, and mechanical properties along with rubber-like elasticity. Think of flexible TPU has a hybrid material between hard plastic and soft silicone.

In 3D printing technology, usually Acrylonitrile Butadiene Styrene (ABS) and Polylactic acid (PLA) are considered as standard plastics for printer filament but due to insufficient flexibility, they can’t be used in bending prototypes. On the other hand, TPU printing filament is flexible in nature. It can bend easily without any effect on the design, strength and durability. A mild soap can be used for its cleaning.

In a study published in the Journal of biomedical materials research. Part A. , it has been found that TPU filaments are better than polyvinylidene fluoride (PVDF) in preparing porous meshes that are more elastic, structurally stable, and retain effective porosity under mechanical pressures. Moreover, TPU mesh have superior biocompatibility with PVDF.

TPU Flexible Filament Sizes and Storage

TPU 3D filament diameters are typically either 1.75mm or 3mm. Flexible TPU filaments can be stored in a cool airtight container. Container may also have a desiccant pack, so that filament bone remains dry. This container can also help in preventing the entry of dirt and dust particles, so that the filament could be used anytime for print. Although some type of TPUs are water-resistant, prolonged contact with water could result in degradation of the product.

Printing Specifications for TPU Flexible Filament

The print speed for flexible TPU filament should be in the range of 30 to 50 mm/sec. Layer thickness should be set above 0.1mm. Extrusion temperature can range from 200 to 220˚C with the heated bed platform set around 80 to 100˚C. For optimal results print flexible TPU filaments on direct extruders; however, it is possible to print on Bowden extruders as well. Flexible TPU filaments have the ability to adhere well to most surfaces such as glass, aluminum, Kapton tape, and blue painters tape. It is important to always print in a well ventilated room regardless of the filament type.

Common uses of TPU Flexible Filament

TPU is commonly used in caster wheels, automotive instrument panels, sporting goods, power tools, medical devices, footwear, drive belts, inflatable rafts, and a number of extruded film and sheet applications. TPU is also a good material to be used in the outer cases of mobile devices such as tablets and phones. In a study published in the journal Sensors, it has been reported that TPU can also help in coating of antennas for efficient performance even after many wash cycles. TPU is an outstanding elastomer with toughness and durability, and is a great thermoplastic that bridges the gap between plastic and rubber.