Investigation of Thermophysical Properties of Nanoparticles



Thermal conductivities of fluids upon addition of magnetic nanoparticles have been investigated. Fe3O4 nanoparticles are synthesized using different synthesis methods and are suspended in various oils. The effect of base fluid and the type of magnetic particle on thermal conductivity is investigated in detail. Up to 23% increase in thermal conductivity is obtained with 2 wt% magnetic particles in hexane. The thermal conductivity enhancement is found to depend on the particle concentration, method of preparation and base fluid. The enhancements obtained are higher than those estimated by any theoretical model present in the literature. 

 

 

Merve Yüksel, Cem Levent Altan, Assoc. Prof. Seyda Bucak


POLYMERS FROM RENEWABLE RESOURCES

Cardanol Based Thermosetting Resins

Polymers which have a wide area of applications have become indispensable materials of our modern lives. Today the majority of these polymeric materials are derived from petroleum feedstocks. With the petroleum production facing exhaustion day by day, and the continously increasing petroleum prices which are strongly afffected by socio-political issues, the use of renewable plant based feedstocks for making polymers is not only essential because our petroleum resources are finite but this replacement may also offer economic and environmental advantages as well. In this area much effort has been given to prepare polymers from plant oils since the triglyceride plant oil structure offers many synthetic routes to incorporate them into various polymeric materials. Another plant based resource is the Cashew nutshell liquid (CNSL) which is a natural resin found in the honeycomb structure of the cashew nutshell and is a byproduct of processing cashew nuts. Structure of Cardanol which is the main constituent of CNSL consists of a phenol ring connected to a 15 carbon long hydrocarbon chain with varied double bonds which makes it a very good candidate for styrene replacement and producing new hybrid materials. The aim of this research is to prepare new and functional polymers based on CNSL, a renewable resource. For this purpose commercially epoxidized cardanol and cardanol based bi-functional Bisphenol-A type glycidyl ether epoxy resin will be chemically modified to prepare cardanol based monomers and then these monomers will be homopolymerized and copolymerized with other petroleum based monomers to prepare partially or completely cardanol based functional polymers. One of the most important outcomes of this project is that cardanol which is a renewable resource will replace the petroleum based starting materials partially or completely to prepare new and functional polymers which may have important potential applications. This replacement is not only advantageous environmentally and economically, but also the new synthesized polymers may carry special properties such as fire retardance and improved toughness properties or degredability in aqueous medium due to the unique structure of cardanol.

 

 


Development of Permanent Chemical Hydrogel Films Based on Chitosan and Carboxy Methyl Cellulose (CMC) for Moisture Absorbing Packaging Films

Hydrogels are cross-linked and 3D polymeric networks which can absorb 1000 times greater than their dry weight without disintegrating. They have a very wide range of application areas such as controlled drug delivery systems, tissue engineering, waste water treatment, agriculture, artificial muscle etc. due to their hydrophilic nature and sensitivity to the environmental parameters such as temperature, pH and ionic strength, concentration, electrical field etc. Hydrogels can be prepared by using synthetic or natural polymers. The most commonly used natural polymeric materials in preparation of hydrogels are chitosan, xhantan, pectin, gelatin and cellulose. Humidity is one of the most important factors that causes deterioration in dry foods (biscuits, powder coffee, coffee milk, snacks etc…). In this research, in order to overcome the risks associated with conventional moisture absorbing sachets, hydrogel films having capability to absorb moisture will be developed by using the biodegradable polymers: carboxy-methyl cellulose and chitosan. The physical and chemical hydrogel films will be prepared with the different polymer compositions and the structural analysis of these hydogel films will be performed. The water absorbing capacity, mechanical and thermal performance of developed hydrogel films will be determined.

 

 

Assist. Prof. Erde Can


FUEL CELL MEMBRANES

Developing Alternative Polymeric Membranes for Fuel Cells

Fuel cells represent a clean and environmentally friendly alternative to current technologies of power generation due to savings in fossil fuels, high efficiency of energy conversion and low pollution level. The most important component of a fuel cell is the polyelectrolyte membrane (PEM). The aim of this research is to prepare new polymer electrolyte membranes (PEM) for direct methanol fuel cells (DMFC). Common requirements for a polyelectrolyte membrane in DMFC applications include high ionic conductivity, high chemical and mechanical durability, low methanol permeability at operation conditions and low cost. In order to satisfy these requirements poly(arylene ether sulfones) and their sulfonated derivatives will be prepared. The sulfonate groups are introduced to the polymer structure to increase the proton conductivity of the resulting polymers. However completely sulfonated polymers increase the methanol permeability, therefore to decrease the methanol permeability, the copolymers of the sulfonated and non sulfonated poly(arylene ether sulfone)s will be prepared. These poly(arylenethersulfone) based polymers will also be chemically modified, cross-linked via radical polymerization with differnt co-monomers and the effects of cross-linking and the introduction of the co-monomers on the proton conductivity, methanol permeability, mechanical and thermal properties of the polymers will be investigated.

 

 


Development and Characterization of Poly(arylene ether sulphone) – Zeolite Based Polymer Electrolyte Membranes for Direct Methanol Fuel Cell Applications

The polymeric polyelctrolyte membranes are the most important components of both the Proton Exchange Membrane (PEM) and the Direct Methanol (DM) Fuel Cells. Today the commercially available perfluoro sulfonic acid membranes (eg. Nafion®) are most widely used polyelectrolyte membranes however they have disadvantages like low proton conductivity at high temperatures (>80oC), high methanol cross over (in DMFCs) and high costs. This study aims the preparation of membranes based on sulfonated poly (arylene ether sulfone) (PESS) and their composites with nanosized and/or nanoporous zeolites that have better physical and chemical properties and are cheaper than the Nafion® membrane, for direct methanol fuel cells (DMFC)’s. Common requirements for a polyelectrolyte membrane in DMFC applications include high proton conductivity, high chemical and thermal stability and mechanical durability, low methanol permeability at operation conditions and low cost. In this project, commercial polysulfones, polyether sulfones and polyphenyl sulfones will be sulfonated using chlorosulfonic acid as sulfonating agent and then in order to improve the proton conductivity, thermal stability and mechanical properties and reduce the methanol cross-over of these polymer membranes, Zeolite Beta will be introduced to these different sulfonated polymers and the Poly (aryl ether solfone) / Zeolite Beta nano-composite membranes will be prepared via solution casting method. The prepared membranes will be characterized for proton conductivity, thermal stability, mechanical properties and methanol cross-over.

 

 

Assist. Prof. Erde Can in collaboration with Prof. N. Baç


POLYMERIC BIOMATERIALS



Poly (L-lactide) (PLLA), Poly (ε-caprolactone) (PCL) and Polybutylene succinate (PBS) Based Blends and their Biomaterial Applications

Poly (L-lactide) (PLLA), Polybutylene Succinate (PBS) and poly (ε-caprolactone) (PCL) are biodegradable and biocompatible polyesters that are widely studied for their biomedical applications. This research project involved the preparation of Polybutylene Succinate (PBS)-Polycaprolactone (PCL) blends by melt blending method using poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymer as the compatibilizer and the characterization of the physical and thermomechanical properties as well as the biodegradability and the cytotoxicity of these melt blends in order to explore their use for potential biomaterial applications. In addition, PLLA/PCL based blends prepared via solution casting method using the same compatibilizer have also been characterized for theromechanical properties, biocompatibility and biodegradation rates and the release of a model drug, paclitaxel.

 

 

Assist. Prof. Erde Can in collaboration with Assoc. Prof. S. Malta and Prof. G.T. Köse