Non-isothermal crystallization behaviour of polyamide 12 analogous to multi-jet fusion additive manufacturing process

Warpage of printed parts, especially for multi-jet fusion (MJF) process, is believed to have strong correlation with crystallization shrinkage. Hence, this article investigates the shrinkage phenomenon of polyamide-12 (PA12) during crystallization process. Various cooling rates show that PA12 exhibits different crystallization behaviour, which affect the crystallinity, crystal phase and crystal shrinkage when performed in MJF. The investigation shows that crystallization shrinkage of PA12 coincides with the exothermic reaction of crystallization process. With cooling rate as slow as 0.2 degrees C/min, PA12 sample shrinks 1.64% during the crystallization process with crystallinity calculated at 24.9%. X-ray diffraction (XRD) suggests shrinkage are closely related to lamellar folding and growth of gamma crystal phase within PA12 samples during crystallization. Spherulites are found to be smaller in diameter with faster cooling rate. These investigations provide detailed understanding of the crystallization behaviour of PA12 for MJF process.

Automated summary

This study investigates the shrinkage phenomenon of PA12 during crystallization process, with different cooling rates affecting its crystallization behavior and crystal shrinkage. The crystallization shrinkage of PA12 is found to be closely related to the exothermic reaction during the crystallization process, and XRD suggests that shrinkage are related to crystal growth.