Improving the impact strength of Poly(lactic acid) (PLA) in fused layer modeling (FLM)

Publication date: 7 April 2017
Source:Polymer, Volume 114
Author(s): Lu Wang, William M. Gramlich, Douglas J. Gardner
Polylactic acid (PLA) is one of the most popular thermoplastics for fused deposition modeling (FDM). Attributed to its semi-crystalline nature, the relation between printing parameters and properties are more complicated than amorphous thermoplastics like acrylonitrile-butadiene-styrene (ABS). This study was designed to investigate two printing parameters, layer height (0.2 and 0.4 mm) and plate temperature (30 and 160 °C) on the Izod impact strength of printed PLA. X-ray diffraction (XRD) analysis confirmed the existence of α crystals in parts printed from 160 °C-plate temperature and α′ crystals in those printed at 30 °C-plate temperature. Parts printed with a 160 °C (plate temperature) had higher crystallinity. Polarized optical microscope (POM) observations illustrated that the plate temperature of 160 °C and layer height of 0.2 mm induced higher crystallinity, smaller crystals and interfacial crystal bands. The Izod impact strength of printed PLA at higher plate temperature was up to 114% higher than injection molded PLA made using conventional molding parameters.

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