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ResourcesMaterialsEngineered Thermoplastic Polyurethane (ETPU): What do You Need to Know About This Material?
Polyurethane bush spare parts. Image Credit: nayladen/Shutterstock.com

Engineered Thermoplastic Polyurethane (ETPU): What do You Need to Know About This Material?

Learn about the material's properties, uses, advantages, and toxicity.

Xomety X
By Team Xometry
 6 min read
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This article will go into more detail about what Thermoplastic Polyurethane, Engineering (ETPU) is, how it is made, its properties, use cases, advantages, disadvantages, and its potential health effects on humans. 

What is Engineered Thermoplastic Polyurethane (ETPU)?

On a chemical level, ETPU is a block copolymer that consists of alternating hard and soft segments. Changing the proportion of each of these segments will result in different hardnesses, allowing for significant customization. This methodology stands in contrast to other softening techniques such as adding plasticizers to normal thermoplastics (which tends to weaken the material). The type of hard and soft segments in the ETPU will define the thermoplastic polyurethane properties, including the level of opacity. 

  • Hard segments - These can consist of either aliphatic or aromatic isocyanates. These segments make the material tougher and stronger.
  • Soft segments - These consist of a reacted polyol, either as a polyether or a polyester. These segments give the material its characteristic flexibility.

How is Engineered Thermoplastic Polyurethane Made?

Engineered Thermoplastic Polyurethane (ETPU) plastic is produced by reacting a diisocyanate with one or more diols (long-chain or short-chain diols). The ratios of these constituents can be varied to create a wide range of physical properties.

This material is used as a standard thermoplastic and can be injection molded, blow-molded, compression-molded, 3D printed, or extrusion molded. Additionally, foaming agents can be added to create closed-cell foams for use in shock-absorbing applications.

What Are the Properties of Engineered Thermoplastic Polyurethane, (ETPU)?

The properties of engineered thermoplastic polyurethane (ETPU) are shown in the table below. The values listed represent the typical or average ETPU properties of the material. There are many different grades on the market, so note that some specialized formulations may fall outside the range of the properties listed below.

PropertyRange
Property

Tensile Strength (MPa)

Range

20 to 60

Property

Elongation at Yield (%)

Range

350 to 800

Property

Elastic Modulus (GPa)

Range

0.03 to 0.7

Property

Melting Point (degrees C)

Range

120 to 220

Property

Density (g/cm3)

Range

1.05 to 1.34

Property

Max Operating temperature - Long Exposure (C)

Range

90 to 90

Property

Max Operating temperature - Short Exposure (C)

Range

120 to 135

Property

Thermal Conductivity W/(mK)

Range

0.014 to 0.5

Property

Hardness (Shore Scale)

Range

70A to 88D

Table 1. ETPU Properties

What Are the Uses of Engineered Thermoplastic Polyurethane?

ETPU is used in many different applications primarily due to its flexibility and toughness. Listed below are some of the more common uses for engineered thermoplastic polyurethane.

  • Medical devices: ETPU is ideal for catheters, infusion tubes, medical instrument cables, anesthesia masks, and oxygen masks. These components are often transparent for monitoring purposes and are typically not manufactured with any additives.
  • Automotive TPU applications: ETPU has excellent scratch resistance making it an ideal material for heavy-use items such as gear knobs and instrument buttons.
  • Sporting goods: ETPU materials lend themselves well to shoe cushions and shock absorbers, thanks to the material's flexibility and weather resistance.
  • Industrial tools: ETPU is ideal for ergonomic grips on tools such as drills or other hand tools. The flexible ETPU is often overmolded onto more rigid thermoplastic materials.
  • Laminates: ETPU is used as a laminate between glass panels due to its excellent optical properties.

What Are the Advantages of Using Engineered Thermoplastic Polyurethane?

The key advantages of thermoplastic polyurethane are:

  • ETPUs are ideal for medical applications as they are biocompatible (provided no additives are used). 
  • Aliphatic ETPUs can be made optically clear and will maintain the same transparency even when exposed to UV radiation. 
  • ETPU remains flexible and impact-resistant even at low temperatures.
  • ETPU is chemically resistant to many solvents and greases.

What Are the Disadvantages of Using Engineered Thermoplastic Polyurethane?

The disadvantages and limitations of Engineered Thermoplastic Polyurethane are: 

  • ETPUs are generally more costly than other commodity thermoplastics.
  • ETPUs are more difficult to process; they must be processed within a narrow temperature range and in very dry conditions.
  • Polyester-based ETPUs easily absorb moisture, causing the materials to decompose over time.
  • Aromatic ETPUs tend to decompose when exposed to UV radiation or heat. If made transparent, this grade of thermoplastic polyurethane also tends to yellow when exposed to UV radiation.

How Does Engineered Thermoplastic Polyurethane Affect Human Health?

ETPU is extensively used in the medical field. However, it must be noted that not all ETPUs are created equal. Among the main sources of potentially harmful chemicals are the various additives used to improve or enhance the properties of ETPUs. As such, medical applications where ETPU products will come in direct contact with tissue typically have no additives. By eliminating these additives, the potential for skin irritation or dermatitis during long-term skin contact is mitigated. At normal temperatures, ETPU does not give off any gasses that can be inhaled. However, if the material is burned, it can produce hazardous gasses.

Is Engineered Thermoplastic Polyurethane Toxic?

If processed correctly, ETPU poses no toxicity risk. It contains no BPA, BPS, or BPF and has not demonstrated any effects on the endocrine or hormonal systems. However, improperly processed ETPU materials may have leftover reactive elements from the polymerization process such as toxic monomers or catalysts. As mentioned previously, some additives may also pose toxicity risks. If burnt, ETPUs can release extremely toxic gasses that contain cyanide compounds. For this reason, ETPUs should not be used in conditions that can cause combustion. The best practice when considering any material is to review the relevant safety data sheet prior to use so that you understand all of the potential safety hazards involved. 

What is the Difference Between Engineered Thermoplastic Polyurethane and Thermoplastic Elastomer?

A thermoplastic elastomer is any thermoplastic material that exhibits elastomeric or rubber-like behavior. As such, ETPU is simply a subset under broader thermoplastic elastomer classification.

Summary

This article summarized the properties, uses, advantages, and toxicity of Engineered Thermoplastic Polyurethane (ETPU).

About Xometry

Xometry offers Thermoplastic Polyurethane (TPU) filament in a variety of color options from Xometry Supplies. We also provide 3D printing services and plastic injection molding services for all of your production needs. Visit our website to explore the full range of our capabilities or to request a free, no-obligation quote.

Disclaimer

The content appearing on this webpage is for informational purposes only. Xometry makes no representation or warranty of any kind, be it expressed or implied, as to the accuracy, completeness, or validity of the information. Any performance parameters, geometric tolerances, specific design features, quality and types of materials, or processes should not be inferred to represent what will be delivered by third-party suppliers or manufacturers through Xometry’s network. Buyers seeking quotes for parts are responsible for defining the specific requirements for those parts. Please refer to our terms and conditions for more information.

Xomety X
Team Xometry
This article was written by various Xometry contributors. Xometry is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding, urethane casting, and more.