Different from other 3D printing techniques such as selective laser sintering (SLS), stereolithography (SLA), three-dimensional printing (3DP), and laminated object manufacturing (LOM), the fused deposition modeling (FDM) technology is widely used in aerospace, automobile making, bio-medicals, smart home, stationery and training aids, and creative gifts for its easy use, simple operation, and low cost. The polylactic acid (PLA) is a material most extensively applied in FDM technology for its low melting point, non-poison, non-irritation, and sound biocompatibility. The FDM 3D-printed PLA parts are a research hotspot in the 3D printing field. This paper is intended to sum up the latest research results and achievements made in recent years in the interface bonding property, mechanical properties, and shape precision promotion of FDM 3D-printed PLA parts as well as the functional expansion of the PLA parts based on vast domestic and overseas literature. The literature research collection focuses on the following two aspects: one is the macroscopic technical research on the optimal settings of key technological parameters; the other one is the PLA modification research on improvement of cross-linking state and crystallinity of PLA molecular chains, carbon reinforced phase modification of PLA, and PLA functional compound modification. The researches in the two aspects are of importance in improving whole properties, enhancing functional applications, and expanding and enriching the applications of FDM 3D-printed PLA parts. This paper is expected to give some helps and references to the researchers who are specializing in the 3D printing field.

A critical review of fused deposition modeling 3D printing technology in manufacturing polylactic acid parts

Additive manufacturing (AM) is a promising technology for the rapid tooling and fabrication of complex geometry components. Among all AM techniques, fused filament fabrication (FFF) is the most widely used technique for polymers. However, the consistency and properties control of the FFF product remains a challenging issue. This study aims to investigate physical changes during the 3D printing of polylactic acid (PLA). The correlations between the porosity, crystallinity and mechanical properties of the printed parts were studied. Moreover, the effects of the build-platform temperature were investigated. The experimental results confirmed the anisotropy of printed objects due to the occurrence of orientation phenomena during the filament deposition and the formation both of ordered and disordered crystalline forms (α and δ, respectively). A heat treatment post-3D printing was proposed as an effective method to improve mechanical properties by optimizing the crystallinity (transforming the δ form into the α one) and overcoming the anisotropy of the 3D printed object.

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Effect of Porosity and Crystallinity on 3D Printed PLA Properties.

This is an accepted manuscript of an article published by Elsevier in Additive Manufacturing on 02/10/2021, available online: https://doi.org/10.1016/j.addma.2021.102378 
The accepted version of the publication may differ from the final published version.

Fused Deposition Modelling: Current Status, Methodology, Applications and Future Prospects

Biodegradable Polymers for Biomedical Additive Manufacturing

Poly (ether ether ketone) (PEEK) is a high-performance engineering thermoplastic polymer with potential for use in a variety of metal replacement applications due to its high strength to weight ratio. This combination of properties makes it an ideal material for use in the production of bespoke replacement parts for out-of-earth manufacturing purposes, in particular on the International Space Station (ISS). Additive manufacturing (AM) may be employed for the production of these parts, as it has enabled new fabrication pathways for articles with complex design considerations. However, AM of PEEK via fused filament fabrication (FFF) encounters significant challenges, mostly stemming from the semi crystalline nature of PEEK and its associated high melting temperature. This makes PEEK highly susceptible to changes in processing conditions which leads to a large reported variation in the literature on the final performance of PEEK. This has limited the adaption of FFF printing of PEEK in space applications where quality assurance and reproducibility are paramount. In recent years, several research studies have examined the effect of printing parameters on the performance of the 3D-printed PEEK parts. The aim of the current review is to provide comprehensive information in relation to the process-structure-property relationships in FFF 3D-printing of PEEK to provide a clear baseline to the research community and assesses its potential for space applications, including out-of-earth manufacturing.

Fused Filament Fabrication of PEEK: A Review of Process-Structure-Property Relationships

Polylactic acid (PLA) is an organic polymer commonly used in fused deposition (FDM) printing and biomedical scaffolding that is biocompatible and immunologically inert. However, variations in source material quality and chemistry make it necessary to characterize the filament and determine potential changes in chemistry occurring as a result of the FDM process. We used several spectroscopic techniques, including laser confocal microscopy, Fourier transform infrared (FTIR) spectroscopy and photoacousitc FTIR spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) in order to characterize both the bulk and surface chemistry of the source material and printed samples. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to characterize morphology, cold crystallinity, and the glass transition and melting temperatures following printing. Analysis revealed calcium carbonate-based additives which were reacted with organic ligands and potentially trace metal impurities, both before and following printing. These additives became concentrated in voids in the printed structure. This finding is important for biomedical applications as carbonate will impact subsequent cell growth on printed tissue scaffolds. Results of chemical analysis also provided evidence of the hygroscopic nature of the source material and oxidation of the printed surface, and SEM imaging revealed micro- and submicron-scale roughness that will also impact potential applications.

Impact of the Fused Deposition (FDM) Printing Process on Polylactic Acid (PLA) Chemistry and Structure

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Alicia M. Elliott

Papers

Impact of the Fused Deposition (FDM) Printing Process on Polylactic Acid (PLA) Chemistry and Structure

Impact of the Fused Deposition (FDM) Printing Process on Polylactic Acid (PLA) Chemistry and Structure

Variations in hippocampal lipid studied by coherent Raman and Infrared micro-spectroscopy in a mouse model of Alzheimer's-related tau pathology.