What cause dark specks and spots on TPU extrudate or TPU injection products

① Contamination in the raw material: TPU is sensitive to contamination from impurities present in the raw material. This can lead to dark specks and spots in the extruded or injection-molded product.

② Screw and barrel contamination: If the screw and barrel are not cleaned properly, leftover resin from previous runs can cause contamination and result in specks and spots.

③  Mold contamination: If the injection mold is not cleaned properly, residual material can cause contamination and result in specks and spots on the final product.

④ Inadequate mixing: If the TPU is not mixed properly during the manufacturing process, it can result in areas of inconsistent color or dark spots.

⑤  Inadequate filtration: If the extrusion or injection equipment is not properly filtered, small particles can get into the material and show up as dark specks or spots.

⑥  Process conditions: If the TPU is exposed to high temperatures for extended periods of time or if the extrusion or injection process is otherwise not optimized, it can result in dark specks or spots.

How to solve the dark specks and spots on TPU extrudate or TPU injection products

1)Processing parameters: Check the processing parameters such as temperature, pressure, and injection time. Adjust them to the optimal range according to the TPU material and injection molding machine used.

2)Purge cleaning: Conduct a purge cleaning of the injection molding machine using a material that has good cleaning performance(such as PP resin and 85A TPU resin). This can help remove any impurities or residues inside the machine. It can also use the professional screw cleaning agent to clean the injection molding machine

3)Mold design: Check the mold design for cracks, scratches, or rough surfaces. These can cause specks and spots on the TPU product. Ensure that the mold is clean and properly maintained.

4)Adding lubricant: Adding lubricant in the TPU resin and fully mixed. The lubricant can reduce materials sticking in the Screw and avoid the TPU is exposed to high temperatures for extended periods of time.

5)Use a different TPU grade: If all else fails, using a different grade of TPU might help to eliminate the specks and spots. Try a different grade with shorter cycle time to see if it helps.