Isı depolayabilen nanokompozit nanoliflerin geliştirilmesi

Thermal management applications are gained importance increasingly in the last decade due to the changings in climates, demand for developed energy conservation as well as improved thermal comfort. Thus, investigation and improvement cost effective, ecologically friendly and simple methods have been the focus of attention by researchers. Organic phase change materials (PCMs), which have the ability to absorb and release large quantities of latent heat during a phase change process, offer remarkable potential to fulfill the growing energy requirements for cooling and heating applications across various industries, including construction, refrigeration, textiles, packaging, solar energy systems, electronics and biomedical materials. A variety of encapsulating and storage processes have been applied to PCMs before integrating them into different composites to prevent their interaction with the surrounding medium, to increase their mechanical and thermal stabilities and to enhance their ease of handling. Recently, the electrospinning technique has been employed as a simple, convenient, and versatile technique for generating form-stable PCMs. In this study, production of bicomponent nanowebs, composed of polyacrylonitrile (PAN) shells and PCM cores were performed via coaxial electrospinning method. Moreover, PCM grafted PAN copolymers were synthesized with developing unique recipe than used as a shell material to produce composite hollow nanofibers. Polyacrylonitrile (PAN) was preferred for its very good thermal stability, high tensile strength and elastic modulus, low density, high moisture management and excellent thermal insulation properties. Polyethylene glycols (PEG), polyethylene glycol methyl ethers (PEGME) and paraffin waxes (n-alkane) were preferred as a PCM to use in the core because of their high latent heat capacities, chemical and thermal stabiliy and ecological friendly properties. The experimental part of the study consist of; determining the appropriate solvents and concentrations of shell and core solutions for electrospinning experiment, synthesis of PCM grafted PAN copolymer and characterizations of them, producing bicomponent nanowebs composed of PAN/PCM as a shell/core with using different concentrations of shell and core solutions, lastly characterizations of produced nanowebs. 4wt% PAN and 6wt% PAN solutions were chosen as a shell material due to better processibility and different concentrations of core materials were used related with their own properties. Synthesized grafted copolymer used in a mixture of shell solution to produce hollow nanofibers. After several trials and fine tuning electrospinning parameters were modified for each pair of shell/core combination. Structural and thermal characterizations of each core and shell material as well as produced nanowebs were performed. Structural properties were determined with fourier transform infrared spectroscopy (FTIR) and thermal behavior were carried out with differential scanning calorimetry (DSC). In addition, nuclear magnetic resonance (NMR) analysis were conducted for synthesized grafted copolymers. Surface images of produced nanowebs were characterized with scanning electron microscopy (SEM) and diameter distribution analysis also performed by ImageJ-DiameterJ program. Also conductivity and viscosity analysis were performed for core and shell solutions. The obtained structural and thermal characterization results showed that desired nanowebs having thermal management feature were achieved for all produced nanoweb composition.