Ali Kilic

Effects of Polarity on Electrospinning Process

As one of the nanofiber production processes, the electrospinning process has a conventional configuration consisting of a charged syringe and a grounded collector plate. In this study, the polarities of the electrodes are reversed so that while the collector is charged by power supply, the syringe is grounded. A solution of 7.5 wt % polyvinyl (alcohol)/water is electrospun. The conventional setup and the new inverse setup are compared in terms of production efficiency and the diameter of the nanofibers is produced. Thus, it is aimed to determine which configuration best suits for an extruder-collector system in an industrial context. Results showed that the conventional setup has a noticeably higher nanofiber production efficiency than the new setup due to a lack of Coulombic force acting on the polymer jet in the new setup. Also, nanofiber diameters and web layer pore sizes produced by the conventional setup are much finer and more homogenously distributed than those produced by the new reversed setup.

A review on non-electro nanofibre spinning techniques

A large surface area, scalable porosity, and versatility have made nanofibres one of the most widely investigated morphologies among the nanomaterials. The characteristic properties of nanofibres have made them useful in a broad range of applications, such as filters, membranes, tissue engineering, wound dressings, protective clothing, reinforcement in composite materials, and sensors. So far, various top-down and bottom-up approaches were proposed to produce nanofibres. In this paper, a comprehensive review is presented on non-electro fiber spinning techniques, along with their mechanisms. The parameters of these techniques are also discussed in detail, while process-specific gains were emphasized according to the end uses. This review paper also provides a literature insight into the biomedical, filtration, optical, and energy applications of nanofibres produced via the most typical and widely used methods.

Proposal of a framework for scale‐up life cycle inventory: A case of nanofibers for lithium iron phosphate cathode applications

Environmental assessments are crucial for the management of the environmental impacts of a product in a rapidly developing world. The design phase creates opportunities for acting on the environmental issues of products using life cycle assessment (LCA). However, the LCA is hampered by a lack of information originating from distinct scales along the product or technology value chain. Many studies have been undertaken to handle similar problems, but these studies are case-specific and do not analyze the development options in the initial design phase. Thus, systematic studies are needed to determine the possible scaling. Knowledge from such screening studies would open the door for developing new methods that can tackle a given scaling problem. The present article proposes a scale-up procedure that aims to generate a new life cycle inventory (LCI) on a theoretical industrial scale, based on information from laboratory experiments. Three techniques are described to obtain the new LCI. Investigation of a laboratory-scale procedure is discussed to find similar industrial processes as a benchmark for describing a theoretical large-scale production process. Furthermore, LCA was performed on a model system of nanofiber electrospinning for Li-ion battery cathode applications. The LCA results support material developers in identifying promising development pathways. For example, the present study pointed out the significant impacts of dimethylformamide on suspension preparation and the power requirements of distinct electrospinning subprocesses. Nanofiber-containing battery cells had greater environmental impacts than did the reference cell, although they had better electrochemical performance, such as better wettability of the electrode, improving the electrodes electrosorption capacity, and longer expected lifetime. Furthermore, material and energy recovery throughout the production chain could decrease the environmental impacts by 40% to 70%, making the nanofiber a promising battery cathode. Integr Environ Assess Manag 2016;12:465-477.

Electrostatic Capture Efficiency Enhancement of Polypropylene Electret Filters with Barium Titanate

This study reports on the effects of BaTiO3—a high dielectric constant additive—addition on charging and filtration properties of meltblown polypropylene (PP) electret filters. Since electrostatic capture efficiency of electret filters is mainly dependent on electrical forces, surface potential and aerosol filtration properties were analyzed and compared. Due to quasi-permanent nature of electret property, stability of charging and filtration performance was also investigated via following an isothermal charge decay procedure. Addition of BaTiO3 did not alter fiber morphology significantly. Particularly, the stability of electrostatic filtration performance was found to be promising with the addition of BaTiO3. Possible microstructural changes after addition of BaTiO3 were investigated via wide angle X-ray diffraction. Changes in crystal structure of PP upon addition of BaTiO3 did not deteriorate electrostatic properties. Copyright 2015 American Association for Aerosol Research

Surface crystallinity of meltspun isotactic polypropylene filaments

In this study, surface crystallinity of meltspun polypropylene (PP) filaments was reported. Results obtained from attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were confirmed with tapping mode atomic force microscopy (TM-AFM) analysis. ATR-FTIR tests were performed directly on longitudinal surfaces of the filaments, where IR radiation penetrates up to a specific depth. TM-AFM measurements were done on microtomed cross-sections of the filaments, which were scanned carefully to investigate stiffness. Annealing enhanced the surface crystallinity of the filaments in a significant way. Interestingly, samples annealed at 70 and 110 °C for 12 h exhibited similar crystallinity on the uppermost 500 nm surface, whereas for the bulk a continuous increase was observed after XRD studies. 12 h annealing at 70 °C modified the endothermic thermogram, while it did not causes significant effect on overall bulk crystallinity. Differences in the behavior of surface and bulk of the fibrous materials should be considered particularly for surface treatment, i.e. plasma, corona discharge, chemical vapor deposition. Results are also pertinent for water and dye absorbency in polymers.

Lignin as an Additive for Advanced Composites

Lignin, an abundant renewable resource material next to cellulose, can be one of the most essential bio-resources as a raw material for the production of environmentally friendly polymers and polymer composites. Due to its chemical structure, lignin can provide additional functionalities in composites. It can be used as reinforcers, fillers, compatibilizers and even stabilizing agents in polymer composites. In this chapter use of lignin in composites, its additional benefits and possible applications were summarized. Structure—process—property relations were particularly emphasized. Because of the aromatic structure and multifunctional side groups, lignin can be a promising, environmentally friendly additive as a free radical scavenger which prevents oxidation reactions. For the structural composite applications, material properties were found to be highly dependent on process conditions. One can observe controversy in the reported mechanical properties of composites with similar components and similar lignin concentrations. Thus in some studies addition of lignin resulted with enhanced strength and modulus; while lignin just acted as a filler in some others. Those studies should be carefully evaluated considering the process conditions. Further improvements can also be achieved after modifying lignin chemically.

Developing lignin-based bio-nanofibers by centrifugal spinning technique

Lignin-based nanofibers were produced via centrifugal spinning from lignin-thermoplastic polyurethane polymer blends. The most suitable process parameters were chosen by optimization of the rotational speed, nozzle diameter and spinneret-to-collector distance using different blend ratios of the two polymers at different total polymer concentrations. The basic characteristics of polymer solutions were enlightened by their viscosity and surface tension. The morphology of the fibers produced was characterized by SEM, while their thermal properties by DSC and TG analysis. Multiply regression was used to determine the parameters that have higher impact on the fiber diameter. It was possible to obtain thermally stable lignin/polyurethane nanofibers with diameters below 500nm. From the aspect of spinnability, 1:1 lignin/TPU contents were shown to be more feasible. On the other side, the most suitable processing parameters were found to be angular velocity of 8500rpm for nozzles of 0.5mm diameter and working distance of 30cm.

Effect of annealing on charging properties of electret fibers

Abstract In the present work, effect of annealing on charging and surface morphology of isotactic polypropylene (PP) filaments was reported. To enhance the surface crystallinity of the filaments, samples were annealed at 70 and 110 °C for 12 h. As expected, fiber surface crystallinity increased upon annealing which led more stable electret fibers. However, the change in the initial surface potential was not so remarkable. The same trend was also observed in filaments containing a commercial nucleating agent, NA11 (sodium 2,2′-methylene-bis(4,6-di-tertbutylphenyl)-phosphate). Surface crystallinity was analyzed using the intensity of specific peaks obtained from attenuated total reflection infrared spectroscopy analysis. The surface charge characteristics of fibers were determined using a modified surface potential decay test.

Ultrasonic coating of nanofibrous webs: a feasible approach to photocatalytic water filters

In this study, we introduce ultrasound-assisted coating as a simple means of functionalizing nanofibrous membranes for photocatalytic (PC) water filtration. TiO2 nanoparticles, which have an anatase crystalline phase with superior PC activity, were directly synthesized over TPU nanofibers and the coated membranes were characterized using scanning electron microscopy (SEM) and X-ray diffractometry. The SEM images confirmed that the addition of polyethylene glycol reduced the nanoparticle dimensions and yielded greater distribution over the nanofibers. UV–Vis analysis demonstrated that Ag decoration over the coating enhanced the PC performance by up to 69.4% following 2-h UV illumination.

Polivinil Alkol (PVA) Nanoliflerin Üretiminde Yenilikçi Bir Yaklaşım: Santrifüjlü Lif Üretimi

Nanolif uretimi uzerine son yillarda one cikan teknolojilerden birisi de santrifujlu lif uretimidir. Yaygin olarak kullanilan yontem olan elektroegirmeye gore, yuksek hizlarda uretim saglamasi ile endustriyel uygulamalara uygundur. Bu calismada, santrifujlu lif uretim yontemiyle biyomedikal uygulamalari, lityum iyon pil elektrotlari gibi katma degeri yuksek urunlerde kullanilabilen polivinil alkol (PVA) nanolifleri uretilmistir. Uretim parametrelerinin (cozelti konsantrasyonu, igne capi, rotor hizi ve igne-toplayici arasi mesafe) lif morfolojisine olan etkileri SEM goruntuleri ile incelenmistir. PVA nanolif uretimi icin %10-15 cozelti konsantrasyonu, 6000-9000 d/dk hiz, 0,5 mm igne capi ve 150 mm civari igne-toplayici arasi mesafe uygun degerler olarak gorulmustur. Ortalama 200 nm’nin altinda capa sahip nanolifler endustriyel uretime olceklendirilebilir hizlarda uretilmistir.