Fused Filament Deposition of PLA: The Role of Interlayer Adhesion in the Mechanical Performances

Abstract

A set of criteria to enhance mechanical performances of standard specimens (Type V, ANSI D368) made of polylactic acid (PLA) were proposed. Fused PLA deposition was conducted with nozzle temperature ranging from 180 to 230 °C and deposition plate temperature ranging from 70 to 110 °C. Optical microscopy, elastic modulus analysis and density measurement allowed emphasizing the effect of temperature field, also measured during the process, on the morphology and the mechanical characteristics of the specimen. Atomic force microscopy revealed a morphology typical of amorphous samples with globular structures. Poor interlayer adhesion was detected in the part of the specimen located at larger distance from the deposition plate, showing an elastic modulus lower than those measured in the central part (220 MPa vs. 500 MPa). The specimen crystallinity degree was below 3%. The molecular weight between entanglements was adopted as a measure of the interlayer molecular diffusion. A successful diffusion and re-entanglement of the polymer melt at the interface was the key to improving mechanical performance. A mathematical model describing the transient heat transfer during the fused PLA deposition and accounting for solidification and the nonisothermal crystallization kinetics was introduced. Simulated temperature evolutions were consistent with the experimental ones. They were related to the mechanical performances, the morphology, and the molecular weight between entanglements of the parts.

Strategies To Modify the Surface and Bulk Properties of 3D-Printed Solid Scaffolds for Tissue Engineering Applications

“…Another study reported that the interlayer adhesion improved with nozzle temperature ranging from 180 to 230 °C and deposition plate temperatures of 70–110 °C. It was also seen that the molecular diffusion in the interlayer space at high temperatures improved the mechanical properties . The elastic modulus of the component increased by >200% (Figure C) .…”

“…It was also seen that the molecular diffusion in the interlayer space at high temperatures improved the mechanical properties. 71 The elastic modulus of the component increased by >200% (Figure 3C). 71 Khosravani et al reported that the printing speed and angle of raster orientation play a significant role in determining the mechanical properties of the PLA samples (Figure 3B).…”

Sterilization of PLA after Fused Filament Fabrication 3D Printing: Evaluation on Inherent Sterility and the Impossibility of Autoclavation

“…However, our results showed that parts with fewer details and stronger structures, such as those used for laboratory supplies, can withstand the autoclaving process without major deformation. Although it was not tested explicitly, our experiences and different studies, such as Rozema et al (1991), suggest that the mechanical properties of FFF-printed parts made from PLA can be strengthened by heat treatment by improving inter-layer adhesion further [ 13 , 30 , 31 , 32 ]. During the printing process, each layer bonds to the layers around it, increasing the structural strength of the entire part.…”

High-performance co-polyesters for material-extrusion 3D printing: A molecular perspective of weld properties

“…The thermocouple was linked directly to a Hi-Speed USB acquisition unit (NI USB-9162) (National Instruments) and the related software allowed to monitor the thermal profile in real time. The measurement of thermal profiles in MatEx using micro-thermocouples is widely adopted in the literature to characterize cooling profiles and for modeling purposes [28][29][30][31].…”