The interlayer stiffness of fused deposition modeled (FDM) parts is significantly impaired by the slow diffusion and re-entangling of polymer chains across filament interfacial welds in the build direction. To mechanically reinforce FDM interfaces, an approach based on timing and spatial direction of stereocomplexation across weld interfaces is introduced via alternating deposition of enantiomerically opposite poly(lactides). Fundamental insight into the kinetics and spatial distribution of homo-and stereocrystallization at FDM interfaces was successfully reconstructed in 2 and 3 dimensions by micrometer resolved Fourier transform infrared microscopy and synchrotron wide-Angle X-ray diffraction tomography. The rate of isothermal stereocomplexation and consequential interfacial stiffening increases with decreased absolute and relative molar masses. The spatial distribution of stereocrystals is governed by the relative molar masses and the extent of interdiffusion, under not only isothermal but also nonisothermal FDM conditions. The net local heat dosage, which depends on print speed, governs the length scales of stereocomplexation and thus mechanical reinforcement. Interfacial stereocomplexation of poly(lactides) in FDM leads to a distinct 40% increase in stiffness and nucleation of bulk filaments, aiding in thermodynamic and geometrical stability.
Bibliographical noteFunding Information:
The authors gratefully thank Stichting Innovatie Alliantie (SIA) and the Province of Limburg for financial support and ESRF for providing beam time for the XRDCT measurements. Corbion Purac is acknowledged for supplying the materials utilized in this study.
Copyright © 2019 American Chemical Society.
- fused deposition modeling (FDM)
- interfacial stereocomplexation
- weld interface
- wide-Angle X-ray diffraction computed tomography
ASJC Scopus subject areas
- Polymers and Plastics
- Process Chemistry and Technology
- Organic Chemistry