Browsing by Subject "Polycarbonate"

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Open Access
Polybenzoxazine based high performance nanofibers via electrospinning
(2016-08) Ertaş, Yelda
Polybenzoxazines are newly developing phenolic type thermoset resins having fascinating properties which overcome the shortcomings of the traditional resins. In recent years, polybenzoxazines are attracting much interest because of their outstanding features, such as near-zero volumetric change upon curing, no by-products during curing, low water absorption, high glass transition temperature and high char yield. In addition, the molecular structure of polybenzoxazines facilitates immense design flexibility which enables tailoring the properties of the cured material for a wide range of application. Electrospinning is a widely used simple and cost-effective technique to produce nanofibers from various polymers, polymer blends, inorganic materials, supramolecular structures and composites. In principle, a continuous filament is formed from polymer solution or melt under high electric field which resulted in fibers with diameters ranging from tens of nanometers to few microns. Nanofibers produced with electrospinning technique show unique physical/chemical properties due to their very high surface area and nanoporous structures. In this thesis, we have produced polybenzoxazine based high performance nanofibrous materials via electrospinning by using two approaches. In the first approach, main-chain polybenzoxazines (MCPBz) were synthesized to produce bead free and uniform nanofibers without using polymeric carrier matrix. However, it was observed that these nanofibers lost the fiber morphology at low temperatures and they formed film before cross-linking. Subsequently, novel photo/thermal curable MCPBz resins were designed and synthesized readily owing to the design flexibility of polybenzoxazines in order to enhance thermal stability of MCPBz nanofibers. Therefore, firstly photo curing was performed to improve the thermal stability of nanofibers and then, thermal curing was carried out at high temperatures to obtain cross-linked MCPBz nanofibers with good thermal and mechanical properties. In addition, it was shown that these cross-linked and highly porous MCPBz nanofibers are very stable in various organic solvents, highly concentrated acid solutions and at high temperatures which make these nanofibers quite useful for the certain filtration applications requiring high temperatures and harsh environmental conditions. In the second approach, we produced polybenzoxazine based composite nanofibers from both polymeric materials and non-polymeric systems (cyclodextrins) with enhanced thermal and mechanical properties. At the same time, PAHs, dye molecules and heavy metal ions removal experiments were performed with polybenzoxazine based composite nanofibers to demonstrate their potential application for the waste water treatment.
Open Access
A portable microfluidic system for rapid measurement of the erythrocyte sedimentation rate
(Royal Society of Chemistry, 2016) Isiksacan, Z.; Erel, O.; Elbuken, C.
The erythrocyte sedimentation rate (ESR) is a frequently used 30 min or 60 min clinical test for screening of several inflammatory conditions, infections, trauma, and malignant diseases, as well as non-inflammatory conditions including prostate cancer and stroke. Erythrocyte aggregation (EA) is a physiological process where erythrocytes form face-to-face linear structures, called rouleaux, at stasis or low shear rates. In this work, we proposed a method for ESR measurement from EA. We developed a microfluidic opto-electro-mechanical system, using which we experimentally showed a significant correlation (R2 = 0.86) between ESR and EA. The microfluidic system was shown to measure ESR from EA using fingerprick blood in 2 min. 40 μl of whole blood is filled in a disposable polycarbonate cartridge which is illuminated with a near infrared emitting diode. Erythrocytes were disaggregated under the effect of a mechanical shear force using a solenoid pinch valve. Following complete disaggregation, transmitted light through the cartridge was measured using a photodetector for 1.5 min. The intensity level is at its lowest at complete disaggregation and highest at complete aggregation. We calculated ESR from the transmitted signal profile. We also developed another microfluidic cartridge specifically for monitoring the EA process in real-time during ESR measurement. The presented system is suitable for ultrafast, low-cost, and low-sample volume measurement of ESR at the point-of-care.