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Effect of processing conditions on crystallization kinetics during materials extrusion additive manufacturing
Lily A Northcutt1, Sara V Orski1, Kalman B Migler1
1Materials Science and Engineering Division, NIST, Gaithersburg, MD 20899.
Polymer
|April 16, 2019
Summary
Flow-induced crystallization in additive manufacturing (AM) was quantified. Faster crystallization occurred at higher shear rates and lower nozzle temperatures, demonstrating AM processing conditions significantly impact polymer crystallization kinetics.
Area of Science:
- Polymer Science
- Materials Science
- Additive Manufacturing
Background:
- Material extrusion additive manufacturing involves high shear rates during polymer extrusion.
- The impact of flow-induced crystallization (FIC) during additive manufacturing (AM) is not well understood.
- Lack of in situ measurement techniques hinders the study of polymer crystallization in AM.
Purpose of the Study:
- To develop and apply in situ measurement techniques for quantifying crystallinity in extruded polymers during AM.
- To investigate the influence of processing conditions on crystallization kinetics in polycaprolactone (PCL) during AM.
Main Methods:
- Utilized a combination of infrared thermography and Raman spectroscopy for in situ measurements.
- Measured temperature and percent crystallinity of extruded polycaprolactone.
- Varied nozzle temperatures and filament feed rates to study crystallization kinetics.
Main Results:
- Quantified crystallinity as a function of time for extruded polycaprolactone.
- Demonstrated that crystallization occurs faster at higher shear rates.
- Showed that lower nozzle temperatures accelerate the crystallization process.
Conclusions:
- Additive manufacturing processing conditions significantly affect polymer crystallization kinetics.
- Higher shear rates and lower nozzle temperatures enhance flow-induced crystallization during AM.
- The developed in situ techniques provide crucial insights into polymer behavior during AM.
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