Flow-induced crystallization during materials extrusion additive manufacturing

Published

September 10, 2018

Author(s)

Lily Northcutt, Sara Orski, Kalman D. Migler, Anthony Kotula

Abstract

Material extrusion additive manufacturing processes force molten polymer through a printer nozzle at high (> 100 s-1) wall shear rates prior to cooling and crystallization. These high shear rates can lead to flow-induced crystallization in common polymer processing techniques, but the magnitude and importance of this effect is unknown for additive manufacturing. A significant barrier to understanding this process is the lack of in situ measurement techniques to quantify crystallinity after polymer filament extrusion. To address this issue, we use a combination of infrared thermography and Raman spectroscopy to measure the temperature and crystallinity of extruded polycaprolactone during additive manufacturing. We quantify crystallinity as a function of time for the nozzle temperatures and filament feed rates accessible to the apparatus. Crystallization is shown to occur faster at higher shear rates and lower nozzle temperatures. Our measurements provide experimental evidence of the effect of shear flow on polymer crystallization in additive manufacturing.

Citation

Polymer

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.polymer.2018.09.018

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Keywords

additive manufacturing, polymer crystallization, Raman spectroscopy

Citation

Northcutt, L. , Orski, S. , Migler, K. and Kotula, A. (2018), Flow-induced crystallization during materials extrusion additive manufacturing, Polymer, [online], https://doi.org/10.1016/j.polymer.2018.09.018, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=925886 (Accessed November 21, 2024)