Aerojel kullanımı ile ılık hisli malzemelerin geliştirilmesi

The warm sensation is related to the amount of heat extracted from the human skin when it is in contact with a material. This heat extraction can be described by the time dependent heat flux which occurs from the skin to the object. The heat flux depends on the material properties such as thermal conductivity, density and heat capacity. Increasing warm sensation requires decreasing these properties. Urea formaldehyde is a thermoplastic polymer which is most commonly used to make toilet seats. Improving warm sensation of toilet seat has become a good marketing strategy. To enhance the thermal comfort of the seats electric heaters are currently in use. However it raises safety issues because of high possibility of water contact with the heater. This project aims to give the urea formaldehyde based toilet seats to warm sensation by incorporating aerogels which exhibits high resistance to heat flow. Urea formaldehyde grains were mixed with aerogels (silica and resorcinol formaldehyde aerogels) and hot pressed together to obtain an aerogel incorporated composite. Composites were manufactured by hot pressing this mixture at elevated pressures and temperatures in the industrial size hot press molds at the manufacture site of toilet seats. Thermal conductivity and density of the composites were measured. Changes in aerogels' density and pore properties were determined at different pressures with a laboratory scale cold press. Denser aerogels were synthesized to make aerogels more resistant to the composite manufacture pressure. Composites with dense aerogels (0.361-0.48 g/cm3) successfully reduced the thermal conductivity of native urea formaldehyde by up to 40% by using volume fractions up to 0.38. With reduced contact coefficient parameters, up to 45% reduction in the heat flux was obtained. Thermal conductivity of composites was also predicted with effective thermal conductivity models such as Maxwell and effective medium theory (EMT). At lower volume fractions Maxwell and Rayleigh models gave good predictions for the composite thermal conductivity. Effective thermal conductivity of composites with dense silica aerogels were best predicted with EMT.