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Effects of heat treatment on the mechanical properties of 3D-printed polylactic acid: Study of competition between crystallization and interlayer bonding

Ghasemkhani, A ; Sharif University of Technology | 2024

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  1. Type of Document: Article
  2. DOI: 10.1016/j.mtcomm.2024.109266
  3. Publisher: 2024
  4. Abstract:
  5. Fused deposition modeling (FDM) is a popular additive manufacturing technique because of its flexibility, customization, cost-effectiveness, and eco-friendliness. However, due to the layer-by-layer fabrication process and the formation of voids, the mechanical properties of printed parts are lower than other manufacturing techniques. As a solution, heat treatments can effectively mitigate additive manufacturing limitations and improve the mechanical properties of printed parts. The interlayer bonding and subsequently mechanical properties of 3D-printed PLA were affected by the competition between crystallization and chain diffusion of 3D-printed polylactic acid during the heat treatment process. This competition highlights the importance of optimization of heat treatment. Additionally, crystallite growth could cause a reduction in some mechanical properties, like elongation. The size, distribution, and content of voids are also influenced by heat treatment, playing a crucial role in the mechanical properties of 3D-printed parts. In this research, printed samples were heat-treated at temperatures of 75 ºC, 110 ºC, and 130 ºC for two hours. Furthermore, compression-molded samples were fabricated to inspect a comparison of mechanical properties between the traditional and additive manufacturing methods and investigate the effect of layer-by-layer fabrication on these properties. Sample AM-75 showed a 15.5% improvement in bonding strength compared to the non-annealed printed sample, resulting in an increase of 20.2% in tensile strength and 275% in impact strength. Moreover, annealing the sample at 130 ºC resulted in a 7.6% reduction in porosity and a significant improvement of 220% in crystallinity, heat deflection temperature, flexural modulus, and flexural strength, with improvements of 121%, 29.5%, and 15.2% respectively. © 2024 Elsevier Ltd
  6. Keywords:
  7. Additive manufacturing ; Annealing ; Heat treatment ; Mechanical properties ; 3D printing ; Additives ; Cost effectiveness ; Crystallite size ; Impact strength ; Polyesters ; Reduction ; Tensile strength ; % reductions ; Customization cost ; Effect of heat treatments ; Interlayer bonding ; Layer-by-layer fabrication ; Manufacturing techniques ; Material extrusion ; Polylactic acid ; Printed samples ; Crystallinity
  8. Source: Materials Today Communications ; Volume 39 , 2024 ; 23524928 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S2352492824012479