Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Integration of Conductive Additives To Pla-Based Biodegradable Composite Films To Improve Their Electrical, Mechanical, and Physical Characteristics(Wiley, 2025) Rakea, Aisha Muthana; Tirkes, Suha; Yildiz, Umit Hakan; Tirkes, Seha; Tayfun, UmitIn this study, Oltu stone powder (OS) and Fe3O4/mica-based conductive pigment (CP) were compounded with polylactic acid (PLA) to develop bio-based conductive films. Four different concentrations of 1%, 10%, 20%, and 30% of powders were applied to determine their optimal concentration in the PLA matrix. The mechanical, thermomechanical, electrical conductivity, melt-flow, and morphological properties of composite films were reported using the tensile, hardness, and impact tests, dynamic mechanical analyses test, linear four-probe method, and atomic force microscopy (AFM), melt-flow index measurements, and scanning electron microscopy methodology, respectively. According to tensile test results, tensile strength and modulus characteristics of PLA decrease with additive integration. However, the elongation value of PLA declined as OS and CP loadings increased. The maximum tensile performance was attained for composites filled with 20% of both CP and OS. The unfilled PLA's Shore D value rose by including OS and CP. At the same loading levels, carbon-based OS produced comparatively higher hardness values than CP, which comprised iron oxide and alumina silicate. AFM analysis revealed that both CP and OS inclusions caused enhancements in surface roughness as their filling amounts increased. In summary, composite samples exhibiting a 20% loading ratio of both OS and CP showed significantly improved mechanical and thermomechanical performances compared to other composites. Composite films with 1% additives have the potential to be applied in electrostatic packing. Additionally, 3D-printed components can be fabricated using composites for applications where appropriate mechanical resistance and electrical conductivity specifications are required.Article Citation - WoS: 3Citation - Scopus: 3Performance Improvement of Carbon Fiber-Reinforced Abs Composites by Introducing Fullerene Nanoparticles(Wiley, 2025) Akar, Alinda Oyku; Yildiz, Umit Hakan; Tirkes, Seha; Tayfun, Umit; Hacivelioglu, FerdaRecently, polymer composites have been extensively researched in industrial fields such as electrical conductance, ohmic heating, electromagnetic shielding and electrostatic discharge, particularly in engineering polymers reinforced with carbonaceous additions. Herein, fullerene (C60) and short carbon fiber (CF) were incorporated with acrylonitrile-butadiene-styrene copolymer (ABS) using melt-compounding followed by an injection-molding process. Composite samples were produced with contents of 20 wt% of CF besides 0.1, 0.5 and 1.0 wt% of C60. Tensile, impact, hardness and wear tests, conductive atomic force microscopy, dynamic mechanical analysis, thermogravimetric analysis, melt flow index tests and scanning electron microscopy (SEM) were performed to characterize mechanical, electrical, thermomechanical, thermal, melt-flow and structural behaviors of ABS-based composites involving CF and C60. Based on the mechanical test findings obtained for the developed composites, comprising tensile and impact test results, C60 additions contributed to a significant rise in tensile strength and impact resistance of CF-reinforced ABS composites, with a 20% increase in tensile resistance being achieved by introduction C60 into the ABS/CF structure. C60 addition enhanced efficiency by 50% in terms of tensile modulus. Electrical conductivity measurements confirmed that C60 nanoparticles and CF exhibited a synergy. The optimum synergistic ratio of C60/CF was obtained as 0.5/20. The conductive path in the ABS/CF composite system was established by incorporating C60 with different loading amounts. SEM micrographs of composites demonstrated that C60 nanoparticles were dispersed homogeneously into the ABS matrix involving lower amounts of C60. (c) 2025 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.Article Citation - WoS: 4Citation - Scopus: 5Near-Infrared Emissive Super Penetrating Conjugated Polymer Dots for Intratumoral Imaging in 3d Tumor Spheroid Models(Wiley, 2024) Karabacak, Soner; Coban, Basak; Yildiz, Ahu Arslan; Yildiz, Umit HakanThis study describes the formation of single-chain polymer dots (Pdots) via ultrasonic emulsification of nonionic donor-acceptor-donor type (D-A-D) alkoxy thiophene-benzobisthiadiazole-based conjugated polymers (Poly BT) with amphiphilic cetyltrimethylammonium bromide (CTAB). The methodology yields Pdots with a high cationic surface charge (+56.5 mV +/- 9.5) and average hydrodynamic radius of 12 nm. Optical characterization reveals that these Pdots emit near-infrared (NIR) light at a maximum wavelength of 860 nm owing to their conjugated polymer backbone consisting of D-A-D monomers. Both colloidal and optical properties of these Pdots make them promising fluorescence emissive probes for bioimaging applications. The significant advantage of positively charged Pdots is demonstrated in diffusion-limited mediums such as tissues, utilizing human epithelial breast adenocarcinoma, ATCC HTB-22 (MCF-7), human bone marrow neuroblastoma, ATCC CRL-2266 (SH-SY5Y), and rat adrenal gland pheochromocytoma, CRL-1721 (PC-12) tumor spheroid models. Fluorescence microscopy analysis of tumor spheroids from MCF-7, SH-SY5Y, and PC-12 cell lines reveals the intensity profile of Pdots, confirming extensive penetration into the central regions of the models. Moreover, a comparison with mitochondria staining dye reveals an overlap between the regions stained by Pdots and the dye in all three tumor spheroid models. These results suggest that single-chain D-A-D type Pdots, cationized via CTAB, exhibit long-range mean free path of penetration (approximate to 1 mu m) in dense mediums and tumors. The single chain near infrared (NIR) emissive Pdots with high cationic surface charge enable penetration in dense medium such as tumor spheroids. Both colloidal and optical properties of Pdots make them promising fluorescent probe in bioimaging. image