The present study investigates the manufacturing and characterization of poly(lactic acid) (PLA)-based composites with raw and treated Poaceae, with loadings of 5, 10, and 20% wt. Before composite fabrication, the lignocellulosic fillers were analyzed using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and microscopy to assess their chemical composition, thermal stability, and morphological features. Composites were prepared by melting PLA in a molten state with fillers, followed by injection molding. Comprehensive characterization of the obtained composites included microscopic analysis, melt flow index (MFI) testing, and differential scanning calorimetry (DSC), as well as mechanical tests (tensile and bending tests, impact test). The addition of Poaceae fibers to the PLA matrix significantly affected the mechanical and rheological properties of the composites. Incorporating 5% of cooked or alkalized fibers increased the flexural strength by 57% and 54%, respectively, compared to neat PLA. The modulus of elasticity for the composite with 20% alkalized fibers increased by as much as 35%. The fibers acted as nucleating agents, reducing the cold crystallization temperature (T_cc) by up to 15.6 °C, while alkaline residues contributed to an increased melt flow index (MFI). The conducted research provides a valuable basis and insights into the design of sustainable bio-based composites.

Large-scale additive manufacturing (LSAM) using fused granulate fabrication (FGF) offers a potential route for the high-value utilization of recycled thermoplastic composites. This study investigated recycled PA6 containing nominally 30 wt.% glass fibers as a candidate feedstock for large-format FGF. An unmodified reference and formulations containing SF315/PTFE, SF315/U15, and MIX-OH were examined. The granulates were characterized using melt mass flow rate measurements, thermogravimetric analysis, and differential scanning calorimetry, while mechanical properties were compared after injection molding and FGF processing. The best FGF performance was obtained for SF315/PTFE (polytetrafluoroethylene) and SF315/U15. Their tensile strengths reached 117.3 and 118.7 MPa, respectively, compared with 56.8 MPa for the FGF-processed reference. Flexural strengths reached 158.8 and 152.4 MPa, respectively, versus 88.0 MPa for the reference. The tensile and flexural improvements produced by MIX-OH after injection molding were not retained after FGF processing, confirming strong processing-route dependence. Preliminary pull-off screening demonstrated that TPU-bonded polymer–steel joints could be produced. Under the investigated conditions, SF315/PTFE and SF315/U15 were identified as promising recycled PA6/GF30 formulations for large-format FGF and further tooling-oriented development.

The use of incremental technologies in various biomedical fields requires the development of new materials that can meet the needs of new applications. This article delves into the impact of modifying PETG with multifunctional polysiloxanes (0.10 wt.% to 2.5 wt.%) on the properties of composite materials produced for 3D printing in bioengineering applications. The article covers the effects on strength (tensile, flexural), rheological (MFR), thermal (DSC), and surface (WCA) properties. The results obtained in this study indicate that polysiloxane additives have a positive effect on the material’s elasticity and bending strength. Moreover, the results presented are a great example of interdisciplinary research combining chemical knowledge to develop specialized material applications.