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Is TPU Filament Hygroscopic? The Facts Explained

TPU, or Thermoplastic Polyurethane, can hold most chemical materials and withstand high temperatures, making it a popular material for creating 3D printing models. However, some filaments used in 3D printing require unique printing settings and storage to maintain their strength and printability. So, does TPU filament fall into this category? 

TPU filament is hygroscopic and will absorb water from the air if left in a moist environment. To keep TPU in its best condition, store it away from moisture to prevent air bubbles from forming when printing and dehydrate it when necessary. 

So, let’s look at the facts behind the hygroscopic property of TPU. I’ll teach you about the best ways to store TPU and help you determine which printing settings you should use for the best-quality TPU prints. 

How Hygroscopic Is TPU? 

TPU is slightly hygroscopic and will absorb small amounts of moisture from the air. Over a few days of being exposed to humid air, TPU will become saturated with water. 

TPU is not as hygroscopic as many other filaments, but it can become saturated if left in the open. 

Since TPU absorbs water, you should avoid using TPU prints to hold water or other liquids. If your TPU filament gets wet, you’ll need to dry it before you start printing. Otherwise, your TPU will be more difficult to use, and any steam created in the hot end might damage your 3D printer.

Does Moisture Weaken TPU Filament?

Moisture weakens TPU filament. In addition, leaving your TPU wet while printing could cause print errors, failed prints, or damaged printer parts. So, you should keep your TPU as dry as possible. 

Since TPU absorbs humidity from the air, it may become moist even if you keep it away from water. You should store TPU filament in airtight containers to preserve its quality. 

You can still use wet TPU filament for 3D printing. However, this will lower the print quality, and it may even form air bubbles in the material, reducing its durability. So, if you want high-quality results, store your TPU in an airtight container. 

Here are some of the best storage containers for TPU, which are both available on Amazon: 

  • YOOPAI Filament Storage Bag Vacuum Kit: These bags are ideal for sealing up your filament, and they come with handy humidity-indicating cards you can stick in the bag and a hand pump for adjusting moisture levels. 
  • PrintDry Vacuum Sealed Storage Containers: This container is vacuum-sealed, so it’s perfect for storing any hygroscopic filament. It keeps TPU dry since you can suck out the air and ambient humidity with the vacuum pump. 

How Do You Dehydrate Wet TPU Filament? 

So, you left your TPU out for too long– don’t fret. To eliminate the humidity, you can dehydrate filament with a dehydrator, oven, or fancy filament dryer. However, be advised that some filaments may become weaker or more brittle after you dry them. So, you shouldn’t leave your filament out if you can help it. 

You can dehydrate wet TPU filament by heating it at 140 °F (60 °C) for 8-20 hours. You can use your oven, a food dehydrator, or a filament dryer to dehydrate TPU successfully. 

If you are using your oven, ensure that you haven’t set it to more than 140 °F (60 °C), as overheating the material can make it softer. 

A food dehydrator is preferred to dry the filament. Once all the moisture is gone, you can clean the material’s surface and use it for printing. 

Lastly, if you are dedicated to 3D printing, it might be time to get a filament dryer. These devices can be costly, but they sure are worth it! All you have to do is stick your spool in, and the machine will monitor the humidity in the chamber.

The Best 3D Printer Settings for Printing With TPU

You’ll need to set your 3D printer at the optimal settings for each material for the best results. The optimal settings for printing with TPU filament include: 

  • Printing bed temperature: The optimal print bed temperature is 50º C (122º F), although you can set the temperature slightly higher or lower. 
  • Extruder temperature: The extruder or nozzle temperature on the printer should be in the range of 220º C to 250 °C (428º F to 482 °F). This range will keep the material soft and flexible, just over the melting point.
  • Use lower retraction settings: TPU is a flexible material, and it requires a low retraction setting. Higher retraction can cause stringing, artifacts, or the terrible blob of death
  • Adjust the flexibility settings: If you have higher infill settings, you’ll be able to print more robust designs. Lowering the infill settings will improve the printed object’s flexibility. However, make sure you know how to adjust your printer’s flexibility settings to prevent mishaps. 
  • Don’t use fans for cooling: There’s a difference of opinion on whether to use fans for cooling when 3D printing with TPU filament. However, if you set the temperature to the right level, you shouldn’t need fans to cool as they may affect the layers’ smoothness. 

By setting the printing settings correctly for 3D prints, you’ll be able to achieve a high consistency level. However, this takes experience and skill, so keep testing to find the perfect settings for each filament you use.

The Benefits of TPU Filament for 3D Printing

TPU Filament is used for 3D printing primarily because of its high versatility and strength. Other reasons why many 3D printing enthusiasts use TPU for 3D printing include: 

  • Flexibility: TPU filament is highly flexible, and you can easily mold it into any shape at the right temperature. By adjusting the flexibility settings on the 3D printer, you can use TPU to create soft, flexible, or rigid objects. 
  • Abrasion-resistant: Another critical feature of TPU is its resistance to abrasion and chemicals. TPU is an unreactive plastic and will hold most chemical materials, making it the ideal choice for industrial 3D print models. 
  • High melting point: You can heat TPU to 250 °F (121.11 °C) before it starts melting. This material can become soft and flexible when heated, making it ideal for printing more complex objects.
  • High adhesion: TPU has high adhesion properties and won’t warp or curl easily. For this reason, it’s used to create highly accurate 3D prints for a wide range of industrial and educational uses.  

Conclusion

TPU is hygroscopic and will absorb moisture from the air if left in the open. It can become saturated after a day or two. Moisture reduces TPU’s strength and causes imperfections, so it’s best to keep it sealed away and dry. 

To get consistent, high-quality prints from this material, make sure you store TPU filament in an airtight container. If your filament has become moist, you can dry it in a food dehydrator or at low heat in an oven. That way, you’ll get high-quality prints, fewer printing mistakes, and a more durable finished product.