Fused deposition modeling (FDM) is currently the most popular 3D printing method, where thermoplastic polymers are predominantly used. Among them, the biobased poly(lactic acid) (PLA) governs the FDM filament market, with demand higher than supply, since not all grades of PLA are suitable for FDM filament production. In this work, the effect of a food grade chain extender (Joncryl ADR® 4400) on the physicochemical properties and printability of PLA marketed for injection molding was examined. All samples were characterized in terms of their mechanical and thermal properties. The microstructure of the filaments and 3D-printed fractured surfaces following tensile testing were examined with optical and scanning electron microscopy, respectively. Molecular weight and complex viscosity increased, while the melt flow index decreased after the incorporation of Joncryl, which resulted in filaments of improved quality and 3D-printed constructs with enhanced mechanical properties. Dielectric spectroscopy revealed that the bulk properties of PLA with respect to molecular mobility, both local and segmental, were, interestingly, not affected by the modifier. Indirectly, this may suggest that the major effects of the extender are on chain length, without inducing chain branching, at least not to a significant extent.

In this work, polymer nanocomposite films based on poly(L-lactic acid) (PLLA) were reinforced with mesoporous silica nanoparticles, mesoporous cellular foam (MCF) and Santa Barbara amorphous-15 (SBA). PLLA is a biobased aliphatic polyester, that possesses excellent thermomechanical properties, and has already been commercialized for packaging applications. The aim was to utilize nanoparticles that have already been established as nanocarriers to enhance the mechanical and thermal properties of PLLA. Since the introduction of antibacterial properties has become an emerging trend in packaging applications, to achieve an effective antimicrobial activity, micro/nano 3D micropillars decorated with cone- and needle-shaped nanostructures were implemented on the surface of the films by means of thermal nanoimprint lithography (t-NIL), a novel and feasible fabrication technique with multiple industrial applications. The materials were characterized regarding their composition and crystallinity using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD), respectively, and their thermal properties using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Their mechanical properties were examined by the nanoindentation technique, while the films’ antimicrobial activity against the bacteria Escherichia coli and Staphylococcus aureus strains was tested in vitro. The results demonstrated the successful production of nanocomposite PLLA films, which exhibited improved mechanical and thermal properties compared to the pristine material, as well as notable antibacterial activity, setting new groundwork for the potential development of biobased smart packaging materials.

This work aims to improve the properties of poly(lactic acid) (PLA) for future biomedical applications by investigating the effect of montmorillonite (MMT) nanoclay on physicochemical and mechanical behavior. PLA nanocomposite filaments were fabricated using different amounts of MMT (1.0, 2.0, and 4.0 wt.%) and 2 wt.% Joncryl chain extenders. The 3D-printed specimens were manufactured using Fused Filament Fabrication (FFF). The composites were characterized by Gel Permeation Chromatography (GPC), Melt Flow Index (MFI), X-ray Diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The thermal properties were studied by means of Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Moreover, the hydrophilicity of the PLA/MMT nanocomposites was investigated by measuring the water contact angle. The mechanical behavior of the PLA/MMT nanocomposites was examined with nanoindentation, compression tests, and Dynamic Mechanical Analysis (DMA). The presence of Joncryl, as well as the pretreatment of MMT before filament fabrication, improved the MMT distribution in the nanocomposites. Furthermore, MMT enhanced the printability of PLA and improved the hydrophilicity of its surface. In addition, the results of nanoindentation testing coupled with Finite Element Analysis showed that as the MMT weight fraction increased, as well as an increased Young’s modulus. According to the results of the mechanical analysis, the best mechanical behavior was achieved for PLA nanocomposite with 4 wt.% MMT.

In this work, the effect of two different types of bioactive coatings on the properties of 3D printed poly(lactic acid)/montmorillonite (PLA/MMT) nanocomposite scaffolds was examined. To improve their suitability for bone tissue engineering applications, the PLA nanocomposite scaffolds were coated with (i) ordered mesoporous Strontium bioglass (SrBG) and (ii) SrBG and nanohydroxyapatite (nHA) using a simple dip coating procedure. The effect of the coatings on the morphology, chemical structure, wettability and nanomechanical properties of the scaffolds was examined. The hydrophilicity of PLA nanocomposite scaffolds increased after the SrBG coating and increased even more with the SrBG/nHA coating. Moreover, in the case of PLA/MMT/SrBG/nHA 3D printed scaffolds, the elastic modulus increased by ~ 80% and the hardness increased from 156.9 ± 6.4 to 293.6 ± 11.3 MPa in comparison with PLA. Finally, the in vitro biocompatibility and osteogenic potential were evaluated using bone marrow-derived stem cells. The coating process was found to be a fast, economical and effective way to improve the biomineralization and promote the differentiation of the stem cells toward osteoblasts, in comparison with the neat PLA and the PLA/MMT nanocomposite scaffold. Graphical abstract

Poly(lactic acid) (PLA) is a readily available, compostable biobased polyester with high strength and toughness, and it is excellent for 3D printing applications. Polymer blending is an economic and easy way to improve its properties, such as its slow degradation and crystallization rates and its small elongation, and thus, make it more versatile. In this work, the effects of different 2,5-furan dicarboxylic acid (FDCA)-based polyesters on the physicochemical and mechanical properties of PLA were studied. Poly(butylene furan 2,5-dicarboxylate) (PBF) and its copolymers with poly(butylene adipate) (PBAd) were synthesized in various comonomer ratios and were blended with 70 wt% PLA using melt compounding. The thermal, morphological and mechanical properties of the blends are investigated. All blends were immiscible, and the presence of the dispersed phases improved the crystallization ability of PLA. Mechanical testing revealed the plasticization of PLA after blending, and a small but measurable mass loss after burying in soil for 7 months. Reactive blending was evaluated as a compatibilizer-free method to improve miscibility, and it was found that when the thermal stability of the blend components allowed it, some transesterification reactions occurred between the PLA matrix and the FDCA-based dispersed phase after 20 min at 250 °C.