TPU extrusion is widely used for tubes, hoses, films, cable jackets and profiles because of its flexibility, abrasion resistance and mechanical strength.

However, TPU extrusion can sometimes cause problems such as bubbles, rough surfaces, unstable output or die lines.

Many of these problems can be traced back to a few key factors: moisture, temperature, extrusion speed, die condition and material handling.

TPU Extrusion Troubleshooting Overview

Extrusion Problem First Factors to Check
Bubbles Material moisture, dryer operation, melt temperature and contamination
Rough surface Drying, melt and die temperatures, cleanliness and output rate
Extrusion surging Feeding stability, barrel temperature, screw speed and material bridging
Die lines or surface marks Die cleanliness, temperature uniformity and material moisture
Tacky or blocking surface Melt temperature, cooling, extrusion speed and TPU grade selection

1. Bubbles in TPU Extrusion

Possible causes include:

  • High moisture content
  • Melt temperature too high
  • Excessive shear
  • Contamination
  • Material degradation

Moisture is one of the first things to check. TPU should be properly dried before extrusion because absorbed moisture can cause bubbles, surface defects and process instability.

Solution: Check the moisture level of the TPU pellets and confirm that the dryer is operating correctly. Then review the melt and die temperatures and reduce excessive shear where necessary.

For more information about preparation before processing, see our TPU Drying Guide.

2. Rough Surface

A rough or uneven extruded surface can result from:

  • Insufficient drying
  • Melt temperature too low
  • Die temperature too low
  • Contamination
  • Excessive extrusion output
  • Improper die design

Solution: First check material moisture and cleanliness. Then adjust the melt and die temperatures gradually and verify that the extrusion rate is appropriate for the selected TPU grade.

3. Extrusion Surging

Surging means that extrusion output, melt pressure or product dimensions fluctuate during production.

Possible causes include:

  • High moisture
  • Incorrect barrel temperature
  • Extrusion speed too high
  • Material bridging in the feed zone
  • Improper screw or die configuration

Solution: Check the drying conditions first, then review barrel temperatures, screw speed and feeding stability.

Stable material feeding and properly controlled processing conditions are essential for consistent TPU extrusion.

4. Die Lines or Surface Marks

Visible lines or marks on the extruded TPU may be caused by:

  • Moisture
  • Material buildup inside the die
  • Contamination
  • Uneven die temperature
  • Incorrect melt temperature

Solution: Clean the die, check temperature uniformity and make sure the TPU resin is properly dried before processing.

5. Tacky or Blocking Surface

TPU can sometimes become sticky during extrusion, especially when the melt temperature is too high or cooling is insufficient.

Recommended checks include:

  • Check melt and die temperatures
  • Improve cooling
  • Adjust extrusion speed
  • Confirm that the selected TPU grade is suitable for the application

Cooling conditions are particularly important for films, tubes and profiles. Allowing the extrudate to contact or wind before it is sufficiently cooled can increase blocking.

A Simple TPU Extrusion Troubleshooting Checklist

When an extrusion problem occurs, check these factors in order:

1. Material moisture
Is the TPU sufficiently dry?

2. Temperature
Are the barrel and die temperatures within the recommended range?

3. Extrusion speed
Is the output too high for the selected grade?

4. Equipment
Are the screw, die and feed system clean and properly configured?

5. Material selection
Is the TPU grade suitable for the specific extrusion application?

Important Processing Note

Processing windows can vary according to TPU chemistry, hardness, extrusion equipment and product design. A setting that works for one grade may not be suitable for another.

Always follow the Technical Data Sheet (TDS) of the specific TPU grade. Make one process adjustment at a time and record the result so that the true cause of the defect can be identified.

Conclusion

Most TPU extrusion problems do not have just one possible cause. Moisture, temperature, equipment and processing speed often interact with each other.

Starting with material drying and then checking processing conditions step by step can help identify the source of the problem more efficiently.

For consistent results, follow the TDS of the specific TPU grade and adjust the process according to the actual application.

For TPU grade selection or extrusion support, contact Longyixing Chemicals with your application, hardness, extrusion equipment and current processing conditions.