Improving Mechanical Properties for Extrusion-Based Additive Manufacturing of Poly(Lactic Acid) by Annealing and Blending with Poly(3-Hydroxybutyrate).

Sisi Wang,Karen De Clerck,Rudinei Fiorio,Dagmar R D’Hooge,Maling Gou,Lode Daelemans,Ludwig Cardon

doi:10.3390/polym11091529

Abstract

Based on differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, polarizing microscope (POM), and scanning electron microscopy (SEM) analysis, strategies to close the gap on applying conventional processing optimizations for the field of 3D printing and to specifically increase the mechanical performance of extrusion-based additive manufacturing of poly(lactic acid) (PLA) filaments by annealing and/or blending with poly(3-hydroxybutyrate) (PHB) were reported. For filament printing at 210 °C, the PLA crystallinity increased significantly upon annealing. Specifically, for 2 h of annealing at 100 °C, the fracture surface became sufficiently coarse such that the PLA notched impact strength increased significantly (15 kJ m−2). The Vicat softening temperature (VST) increased to 160 °C, starting from an annealing time of 0.5 h. Similar increases in VST were obtained by blending with PHB (20 wt.%) at a lower printing temperature of 190 °C due to crystallization control. For the blend, the strain at break increased due to the presence of a second phase, with annealing only relevant for enhancing the modulus.

Highlights

Additive manufacturing (AM), or 3D printing, enables the production of physical objects through the decomposition of successive layers of material
We evaluated how the mechanical and thermal properties of poly(lactic acid) (PLA) printed parts could be improved using a wide range of experimental characterization techniques, including scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, polarizing microscope (POM), and scanning electron microscopy (SEM), to examine the optimal processing conditions and the effects of variations in PHB blending and annealing, or a combination of both
S5 of the from Analysis of variance (ANOVA) analysis indicated that this increase was insignificant (Table S5 of the SI)

Summary

Introduction

Additive manufacturing (AM), or 3D printing, enables the production of physical objects through the decomposition of successive layers of material. Annealing increases diffusion between distinct particle morphologies, bonding of beads, and crystallinity [10,16,25] The latter plays a specific and important role in semi-crystalline polymers likely by improving the mechanical and thermal stability of the resulting product [13,17,26,27,28,29]. We evaluated how the mechanical and thermal properties of PLA printed parts could be improved using a wide range of experimental characterization techniques, including scanning calorimetry (DSC), X-ray diffraction (XRD) analysis, polarizing microscope (POM), and scanning electron microscopy (SEM), to examine the optimal processing conditions and the effects of variations in PHB blending and annealing, or a combination of both. The present study closed the gap in applying conventional processing optimizations for the field of 3D printing, taking into account sustainability

Materials and Processing

Characterization

Structure

Results and Table

Effect of Blending PLA with PHB

Conclusions