Observations and Origin of Interfacial Heterogeneities in High-Performance Engineering Thermoplastics During Additive...

Area of Science:

• Materials Science
• Additive Manufacturing
• Polymer Science

Background:

• Heterogeneity in 3D printed polymers challenges mechanical performance.
• Poor inter-road adhesion is a common issue in extrusion-based 3D printing.
• Controlling material properties during printing is crucial.

Purpose of the Study:

• Investigate the origins of heterogeneity in 3D printed parts.
• Map the formation and evolution of crystallinity in polyether ether ketone (PEEK).
• Understand the impact of printing process on material properties.

Main Methods:

• Utilized synchrotron-based in situ X-ray microdiffraction.
• Employed infrared pyrometry for temperature mapping.
• Analyzed single-road-width, two-road-tall PEEK prints.

Main Results:

• Crystallinity in the second printed road forms slower but achieves higher order than in single-road prints.
• The first road cools faster than the second due to print bed thermal conductivity.
• Significant cold crystallization occurs in the first road upon deposition of the second road, creating a sharp gradient.

Conclusions:

• Cold crystallization in underlying layers is a general phenomenon in multi-layered 3D prints.
• This induced cold crystallization contributes to poor inter-road and interfacial adhesion.
• Understanding these gradients is key to improving 3D printed polymer performance.