What is TPU Filament in 3D Printing? Material Properties and Applications

3D printing flexible parts can be a challenge. While technologies like injection molding can easily process liquid silicone rubber and various thermosets, 3D printing finds it more difficult to do so. Most 3D printed parts are therefore rigid.

That being said, there are several good options for 3D printing flexible parts. Stereolithography (SLA) 3D printers can print elastomeric resins, while advanced 3D printing technologies like HP’s Multi Jet Fusion can print specialized flexible materials to a very high standard. Silicone 3D printing has also shown promise in recent years — though it is still in its infancy.

But perhaps the best way to 3D print flexible parts is with thermoplastic polyurethane (TPU). Offering rubber-like material properties, TPU can be used with common 3D printing processes like fused deposition modeling (FDM), enabling virtually anyone to “stretch” the rules of 3D printing.

What is TPU Filament?

TPU filament like Stratasys FDM TPU 92A is highly flexible (image: Stratasys)

Thermoplastic polyurethane is a type of polyurethane plastic belonging to the thermoplastic elastomer (TPE) family. It is elastic like rubber but also strong like plastic.

On a chemical level, TPU is a block copolymer made up of alternating sequences of hard segments (isocyanates) and soft segments (reacted polyol). The manufacturer determines the ratio between them; the more soft segments, the greater the material’s flexibility. [1] Due to this variability, the shore hardness of TPU can range from 60A (similar to mild silicones) to 80D (equivalent to nylons or rigid PVC). [2]

In terms of practical use, TPU offers desirable material properties like flexibility, good tensile strength, and resistance to tears and abrasions. It has emerged as one of the best materials for 3D printing flexible parts, with many applications in consumer products and industrial parts. And unlike other TPE materials, it has good thermal stability and is fairly easy to print using an FDM 3D printer.

TPU is available in different forms to suit different manufacturing technologies. In 3D printing, manufacturers have developed it as both a filament (for FDM) and a powder (for SLS).

Recommended reading: Can You 3D Print Silicone?

TPU Material Properties

TPU offers some material properties typically found in rubbers and others typically found in plastics. Its principal advantage is its merging of the powerful properties of rubber with the workability of plastics: it is much easier to 3D print than comparable elastomeric materials.

The main material properties of TPU include:

Elasticity

TPU is a flexible elastomer that can behave like rubber. Though it lacks the performance of true rubber, it can bend and compress. These properties also contribute to desirable attributes such as shock resistance and vibration dampening. The elasticity of TPU can even be controlled by modifying its composition. Some TPU materials are hard, while some are much more pliable. This tunability allows TPU to be used in a wide range of products, from flexible phone cases to industrial seals.

High Elongation and Tensile Strength

In comparison to other thermoplastics in the TPE family, TPU offers high tensile strength, elongation, and tear resistance, enabling its use in products that need to endure constant stretching and bending. This makes the material particularly valuable in demanding industrial applications — as a material for gaskets and hoses, for example.

Low-Temperature Performance

Unlike some flexible materials, TPU retains its elasticity even at low temperatures and is resistant to cold cracking. This makes it useful for a range of temperature-specific applications, from vehicle components to winter sports products like ski boots.

Abrasion Resistance

TPU is resistant to surface damage, making it a preferred material for applications exposed to friction and wear, such as conveyor belts, protective cases, and industrial rollers. Its ability to endure rough handling ensures long-lasting performance in both commercial and industrial uses. The abrasion resistance of TPU can be further improved when it is reinforced with glass fibers or blended with polymers like PVC.

Chemical Resistance

In addition to its resistance to abrasions, TPU is a good repeller of chemicals, especially oil and grease. Polyester TPUs are best for resisting oils, while polyether TPUs are typically used in moist environments (where the material’s hygroscopic properties must be minimized). TPU’s chemical resistance extends to many industrial solvents, fuels, and cleaning agents, making it suitable for automotive components, fuel hoses, and industrial storage containers.

UV and Weather Resistance

TPU is naturally resistant to UV radiation and weathering, making it an excellent choice for outdoor applications. It can endure prolonged sun exposure without significant degradation, which is critical for products like outdoor cables, roofing membranes, and protective coatings.

Biocompatibility

Certain types of TPU are biocompatible, meaning they can be safely used in medical applications. Medical-grade TPUs are commonly employed in devices such as catheters, surgical tubing, and prosthetics due to their flexibility, strength, and chemical resistance.

Pros and Cons of TPU

TPU Applications

TPU filament can be used for 3D printed prosthetic devices

The material properties of TPU — some of which are rarely found in 3D printing materials — make it suitable for a wide range of practical uses.

In the industrial sector, the durability and chemical resistance of TPU contribute to its use in products like gaskets, seals, and tubing (softer TPU), as well as items like caster wheels (harder). 3D printing giant Stratasys recommends its FDM TPU 92A material for products like air ducts and vibration dampeners. [3]

TPU is also a valuable 3D printing material in the automotive industry. Manufacturers use it for printed flexible parts like air intake hoses, side moldings, and seating sections, while its color adaptability allows manufacturers to make cosmetically suitable parts for different car models.

Although TPU is not as medically safe as silicone, the medical sector uses thermoplastic polyurethanes in hospital beds, gel shoe orthotics, and wearable monitor devices. The material can also be used as cable insulation for medical instrument cables and for 3D printed prosthetics and orthotics.

Many consumer products utilize TPU. The durability and soft texture of printed TPU is particularly attractive for product designers, and the material can therefore be found in items like TPU footwear and raincoats, as well as protective casings for smartphones and other electronic products. Manufacturers can also produce soft-grip handles for products like power tools or toothbrushes using TPU.

The sporting goods industry is another beneficiary of TPU. The low-temperature performance and abrasion resistance of the material makes it ideal for winter sports products such as ski boots and in-line skating equipment.

TPU 3D Printing Technologies Compared

The main additive manufacturing technologies used to 3D print TPU are fused deposition modeling and selective laser sintering. These technologies differ significantly: FDM is an extrusion process that processes spools of filament; SLS is a powder bed process that sinters particles of powder.

FDM is more widely used than SLS in the fabrication of TPU 3D printed parts (due to its overall market dominance), but both technologies have their respective advantages.

Note, however, that FDM and SLS are not the only 3D printing technologies used to print flexible materials. SLA and PolyJet 3D printers, for example, can print other types of flexible 3D printing material; SLA pioneer Formlabs recommends its proprietary Elastic Resin as a suitable alternative to 50–60A TPU.

Additionally, TPU and other elastomers can be processed with non-additive technologies like injection molding and CNC machining.

TPU Extrusion 3D Printing

TPU filament is the most common flexible material for FDM 3D printing

Fused deposition modeling (FDM) or fused filament fabrication (FFF) is the most popular 3D printing process, largely thanks to its use in rapid prototyping and the consumer space. To print TPU with an FDM 3D printer, one can purchase TPU filament, popular varieties of which include NinjaTek NinjaFlex, Polymaker PolyFlex, and Stratasys FDM TPU 92A.

One of the major advantages of FDM TPU 3D printing is accessibility. FDM printers are affordable — far more so than SLS machines — which allows a range of non-industrial companies to fabricate TPU components.

A drawback of the technology is its print quality. FDM offers lower dimensional accuracy than SLS, and printed parts can show visible layer lines on the surface. For this reason, FDM is often used for TPU prototypes or non-cosmetic parts rather than end-use products.

Recommended reading: What Material Is Used for 3D Printing? A Guide to Polymer FDM Filaments

How to Print TPU Filament

Users of FDM technology should note that the printing of TPU (and other flexible filaments) requires special attention. To successfully print the material, the following guidelines should be observed:

• Use direct drive extruders: To prevent TPU coiling up within the extruder, users should print with a direct drive extruder as opposed to a Bowden extruder.
• Mount the filament spool above the extruder: During FDM printing, filament is gradually unwound from the spool as it is pulled by the extruder. But since TPU is elastic, pulling it can cause it to stretch rather than unwind the spool. By mounting the spool above the extruder, gravity reduces the required pulling force.
• Moderate print temperature: TPU filament prints best at 224–250 °C, according to material developers like NinjaTek. [4]
• Slow print speed: TPU does not print well at high speeds, because it can easily compress and cause jams, leading to print failure. A feed rate of no more than 20 mm/s works best.
• Disable or minimize retraction: Retraction is a useful feature of FDM 3D printers designed to prevent stringing and unwanted material blobs. However, TPU is sensitive to fast extruder movements, and retraction — during which the nozzle pulls back excess material — can negatively affect print quality.
• Lower layer heights: Lower layer heights permit slower feed rates, which lead to better TPU prints. Printing software company Simplify3D recommends layer heights in the range of 0.1–0.2 mm. [5]

TPU Selective Laser Sintering

Formlabs is one company that produces high-performance TPU powder for SLS (image: Formlabs)

SLS is a powder bed additive manufacturing process widely used at professional and industrial levels; unlike FDM, there is no consumer market for it. Printing TPU parts with an SLS system requires TPU powders, such as DuraForm TPU Elastomer from 3D Systems or Sinterit’s FlexaSoft.

Although less accessible and affordable than FDM, SLS offers advantages such as improved dimensional accuracy, better mechanical performance, the ability to print complex overhanging sections, powder recycling options, and freedom from support structures (also eliminating the labor-intensive post-processing step of support removal).

The high cost of SLS hardware means that companies may be more likely to order on-demand SLS TPU parts from a 3D printing service bureau like Shapeways or Sculpteo. These companies can determine the required settings for a print themselves. However, as with flexible FDM filaments, SLS powders require special considerations.

How to Print TPU Powder

Service bureau Shapeways recommends the following design guidelines for parts printed with EOS TPU 1301:

• Minimum wall thickness of 0.7 mm
• Minimum supported wire diameter of 1.0 mm
• Minimum unsupported wire diameter of 2.0 mm
• Minimum 1.0 mm height/width for embossed details
• Minimum 1.5 mm height/width for engraved details
• Use of escape holes to facilitate powder removal: minimum 4.0 mm diameter (single hole) or 3.0 mm (multiple holes)
• Minimum clearance of 1.0 mm between individual parts on the print bed
• Minimum sprue thickness of 1.5 mm; at least two per part [6]

TPU Multi Jet Fusion

Multi Jet Fusion is an advanced alternative to FDM (image: Materialise)

Multi Jet Fusion (MJF) from HP is an advanced 3D printing technology well-suited for producing TPU materials like Ultrasint TPU 90A-01. This process uses precise layers of powdered TPU fused by heat and chemical agents, enabling high-detail, functional prints.

Ultrasint TPU 90A-01, known for its Shore 90A hardness, offers excellent elasticity, durability, and abrasion resistance. MJF enhances these properties by producing parts with consistent mechanical performance, smooth surfaces, and intricate geometries. Its low porosity and isotropic strength make it ideal for demanding applications.

Typical uses include footwear midsoles, automotive seals, and flexible protective gear. MJF’s scalability also supports short-run manufacturing and customization, making it popular in industrial and consumer product development.

TPU Filament Shore Hardness

TPU filament is available in a range of shore hardness values, allowing FDM printer users to deploy the material for a wide variety of end uses. The table below shows the most common shore hardness values of TPU and their associated properties.

TPE vs TPU Filament

We have looked at the properties, benefits, and applications of TPU, but what is the difference between TPU and TPE, another go-to flexible 3D printing material?

TPE, which stands for thermoplastic elastomer, is a family of flexible materials that includes thermoplastic co-polyester (TCP), thermoplastic polyamide (TPA), and — confusingly — TPU. The technical difference between TPE and TPU is therefore one of specificity: TPE is a group of several materials, while TPU is a specific material within that group.

So if TPU is simply a form of TPE, why is it that many material developers offer a direct choice between TPU and TPE 3D printing material? Unclear though it may be, this is a matter of common usage: in 3D printing, TPE tends to refer to softer, more flexible materials within the TPE spectrum, while TPU is the harder, more durable option.

TPU is a more recent addition to the 3D printing materials market, and it is more commonly used for high-performance parts due to its superior durability. TPU is also easier to print on an FDM 3D printer than soft TPE, which is more prone to clogging and stringing. Perhaps for this reason, Stratasys manufactures TPE in SLS powder form and TPU in FDM filament form.

Conclusion

Thermoplastic polyurethane (TPU) is a highly versatile material well-suited for a wide range of flexible 3D printing applications. Its unique combination of flexibility, durability, and impact resistance makes it an excellent choice for producing functional, long-lasting parts. While TPU’s softness can pose challenges during the printing process — such as filament feeding issues and adhesion difficulties — its exceptional performance characteristics far outweigh these obstacles when properly managed.

For FDM 3D printer users, success with TPU filament hinges on understanding its specific printing requirements. Conducting multiple test prints allows users to discover optimal settings like print speed, extrusion temperature, and bed adhesion. Once dialed in, users can confidently print durable, shock-absorbing components such as protective cases, flexible joints, and custom-fit wearables.

Businesses and product developers without in-house 3D printing capabilities can easily leverage TPU through professional service bureaus. These services offer advanced printing methods like Selective Laser Sintering (SLS) or Fused Deposition Modeling (FDM), ensuring high-quality TPU parts tailored to precise specifications. This makes TPU accessible even to those new to 3D printing technology.

In conclusion, TPU’s adaptability, from personal DIY projects to large-scale industrial production, highlights its enduring appeal in the 3D printing world. Its ability to combine flexibility with strength ensures its place as a top choice for demanding, performance-driven applications across diverse industries.

Frequently Asked Questions

What is TPU filament?
TPU (Thermoplastic Polyurethane) filament is a flexible, durable, and elastic material used in 3D printing. It belongs to the TPE (Thermoplastic Elastomer) family but stands out due to its superior strength, abrasion resistance, and chemical resistance. TPU is commonly used for applications requiring flexibility, such as phone cases, shoe soles, and gaskets.

What are the key properties of TPU filament?
TPU filament is highly flexible, offering rubber-like elasticity with good tensile strength and elongation. It also has excellent abrasion and chemical resistance, making it ideal for functional parts exposed to wear or harsh environments. Additionally, TPU maintains flexibility at low temperatures and offers impact resistance and shock absorption.

How difficult is it to print with TPU filament?
Printing with TPU can be challenging due to its flexibility, which can cause filament feeding issues. Direct-drive extruders are recommended for better control, though Bowden setups can work with proper tuning. Printing slowly and ensuring consistent bed adhesion can improve results.

What are common uses for TPU filament?
TPU filament is used for applications requiring flexibility, durability, and impact resistance. Common uses include protective cases, flexible joints, seals, belts, and even wearable devices like custom-fit insoles.

Is TPU filament environmentally friendly?
While TPU is not biodegradable, it is recyclable in some setups. Its long lifespan due to its durability reduces the need for frequent replacements, contributing to a more sustainable usage profile.

References

[1] What is TPU? [Internet]. Lubrizol. [cited 2021Oct19]. 

[2] Thermoplastic polyurethanes bridge the gap between rubber and plastics [Internet]. American Chemistry Council. 2002 [cited 2021Oct19]. 

[3] FDM TPU 92A: Flexible elastomer TPU 3D printing material [Internet]. Stratasys. [cited 2021Oct19].

[4] 3D printing with TPU [Internet]. NinjaTek. 2021 [cited 2021Oct19].

[5] Flexible [Internet]. Simplify3D. 2019 [cited 2021Oct19].

[6] TPU plastic 3D printing material information [Internet]. Shapeways. 2021 [cited 2021Oct19].