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    Biodegradable Nanocomposite Filament Based on PLA/PCL/CNCs for FDM 3D Printing: Production, Characterization and Printability
    (Wiley, 2025) Ilhan, Recep; Gumus, Omer Yunus; Lekesiz, Huseyin
    Additive manufacturing (AM) is a widening technique for the processing of polymers that is not only used by personal users but also by some industries. The development of biodegradable and bio-based composites for AM attracts great interest with respect to various aspects such as environmental issues, user health, and biomedical applications. Polylactic acid (PLA) is a good candidate for bio-based materials. However, its brittleness needs to be improved. In this study, PLA-based filaments with improved toughness by adding polycaprolactone (PCL) (10% and 20% by weight) and cellulose nanocrystals (CNCs) (5% by weight) were produced for the fused deposition modeling (FDM) technique. The physical, thermal, morphological, and mechanical properties of the produced filaments were comprehensively characterized. All filament diameters were found to be within the suitable range for FDM applications (1.75 +/- 0.05 mm). TGA analyses showed that the filaments could maintain their thermal stability up to approximately 256 degrees C and that the CNCs enhanced their thermal stability. The addition of PCL and CNCs did not cause significant changes in T g and T m of the neat PLA (T g = 58.14 degrees C and T m = 175.93 degrees C). The tensile test results indicated that the PCL and CNCs reinforcement increased the elongation at break from 6.76% to 40.25% and the toughness from 2.94 to 14.48 MJ/m3. In the last part, the three-dimensional (3D) printability was demonstrated by producing auxetic sheets with optimized printing parameters based on MFI, TGA, and DSC data, and good dimensional stability was obtained.
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    Effects of essential oil on the properties of egg white/polyacrylamide (EW/PAAm) Pickering emulsion hydrogels (PEHs) via UV crosslinking
    (Springer, 2025) Parin, Fatma Nur; Gun, Ahmetcan; Ilhan, Recep; Parin, Ugur
    Currently, several researches have demonstrated that hydrogels are useful for wound healing in a variety of approaches. Herein, Pickering oil-in-water (o/w) emulsion hydrogels were rapidly produced by free radical photopolymerization (UV crosslinking). Egg white (EW) polymer and acrylamide monomer were used as water phase, whereas lavender essential oil was used as oil phase. The bio-based surfactant beta-cyclodextrin was used to stabilize emulsion hydrogels. The introduction of lavender essential oil (LEO) in specific amounts in total emulsion (10 - 50% v/v) was performed. The functional groups in the hydrogels were confirmed by the attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FT-IR). The hydrogels had a swelling ratio of more than 200% and contact angle values of below 70 degrees. The max compression stress of the hydrogels with 20% LEO concentration was 354.98 kPa. The morphology and mechanical characteristics of Pickering hydrogels may be changed by adjusting the increment of LEO concentration in emulsions. Increasing the oil concentration causes droplet diameters to be increased and Young's modulus to be decreased. The hydrogels with LEO concentration of 40-50% showed antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) with 9-12 mm zone inhibition. It was observed that the hydrodegradation phenomena increased with the increment of the lavender oil amount in the total emulsion and reached the highest 80.1% value for 28-day period. In accordance with the findings, the produced hydrogels have the potential to be used as wound dressings in wound healing applications. [GRAPHICS] .
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    Investigation of effects of environmental conditions on wear behaviors of glass fiber reinforced polyester composite materials
    (Wiley, 2025) Korku, Mihriban; Ilhan, Recep; Feyzullahoglu, Erol
    Glass fiber reinforced polymer (GFRP) composites can be subjected to different environmental conditions such as temperature, humidity, ultraviolet radiation, hydrothermal cycle, acidic and alkaline solution in environments where they operate. These environmental conditions cause different damage mechanisms in composites such as pore formation, micro-cracks, delamination, fiber breakage, fiber/matrix interface separation, plasticization, swelling and surface color change. In this study, wear properties of hybrid glass fiber reinforced polymer composites exposed to various environmental conditions for constant load (60 N), speed (500 rpm) and 2 h were examined comprehensively, depending on material content and environmental conditions. In this experimental study, the service conditions in glass fiber reinforced composites were simulated using different artificial aging environments such as acidic environment, hydrothermal cycle and UV radiation. In addition to the material content, it appears that the environmental conditions to which composites are exposed has a significant effect on friction coefficient. Considering environmental conditions, it is seen that the acid environment and hydrothermal cycle have reduced wear resistance of GFRP composites, while UV radiation improved wear resistance of the composites. In C2 sample, the wear rates under different conditions are 1.87 x 10-14 m3/Nm in non-treated sample, 6.05 x 10-14 m3/Nm in acid environment, 4.79 x 10-14 m3/Nm in hydrothermal cycle and 0.59 x 10-14 m3/Nm in UV radiation.Highlights Friction coefficient of glass fiber reinforced polyester (GFRP) is higher under aged condition compared to non-treated. Glass fibers used in correct proportions can reduce friction coefficient in GFRP. GFRP exposed to environmental conditions has an important effect on wear. Acid environment and hydrothermal cycle has reduced wear resistance of GFRP. UV radiation improved wear resistance of GFRP composite. Glass fiber reinforced polymer composites subjected to different environmental conditions. image