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Isotactic polypropylene (iPP)/silica (SiO2) composites were prepared by solution (toluene) mixing followed by either sonication or autoclaving to disaggregate the silica agglomerates. The obtained composite resins were then spun into monofilament fibers using a ThermoHaake's single screw extruder. The obtained fibers were characterized by morphological analyses (scanning electron microscope, atomic force microscopy (AFM), and Raman), crystallization profile (differential scanning calorimetry), and hot-stage microscopy. AFM images and Raman analysis maps revealed that silica particles of a submicron size range were present on the surface. The inclusion of silica particles into the resins resulted in a higher crystallization temperature ( Tc) and shrinkage resistance of the composite fiber when compared to those of the neat or toluene-prepared PP fibers, which were attributed to the nucleating effect of the silica filler with an effective reinforcement. In addition, the silica loadings (0.25–1 wt%) increased the tensile strength attributable to its change in shape from round to elongated and flattened after spinning process, except that the greatest increase (1.4-fold) was seen at 0.25 wt% silica. However, the variances were large, resulting from diameter variation arising from free-fall fibers obtained by gravitational force only. Interestingly, the surface hydrophobicity of the composite fibers was found to be higher than the neat fibers due to the increase in the surface roughness arising from the presence of particles on the surface.

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Functionalities of 3D printing filaments have gained much attention owing to their properties for various applications in the last few years. Innovative biocomposite 3D printing filaments based on polylactic acid (PLA) composited with ZnO nanoflowers at varying contents were successfully fabricated via a single-screw extrusion technique. The effects of the varying ZnO nanoflower contents on their chemical, thermal, mechanical, and antibacterial properties were investigated using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and tensile testing, as well as qualitative and quantitative antibacterial tests, respectively. It was found that the ZnO nanoflowers did not express any chemical reactions with the PLA chains. The degrees of the crystallinity of the PLA/ZnO biocomposite filaments increased when compared with those of the neat PLA, and their properties slightly decreased when increasing the ZnO nanoflower contents. Additionally, the tensile strength of the PLA/ZnO biocomposite filaments gradually decreased when increasing the ZnO nanoflower contents. The antibacterial activity especially increased when increasing the ZnO nanoflower contents. Additionally, these 3D printing filaments performed better against Gram-positive (S. aureus) than Gram-negative (E. coli). This is probably due to the difference in the cell walls of the bacterial strains. The results indicated that these 3D printing filaments could be utilized for 3D printing and applied to medical fields.