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Production and development of de/anti icing fluids for aircraft

Erdoğan, Barış
Aircraft are not allowed to take off prior to cleaning of snow and ice deposits that form on their surfaces under winter conditions to refrain from compromising flight safety. Water based solutions containing mainly ethylene or propylene glycol, or both, are employed either to remove the snow/ice layers or to provide protection against deposition of these layers. The first group of solutions, i.e. de-icing fluids, are Newtonian and have generally low viscosity so that right after their application they fall off the aircraft surfaces, providing little or no further protection against precipitation. Therefore, various anti-icing solutions have then been developed to provide the prolonged protection due to their non-Newtonian and high viscosity characteristics. Although the appropriate ranges of viscosity and surface tension have been determined in a number of studies, actual compositions of these solutions are proprietary. The main objective of this study is to determine the basic interactions between the chemical species in de/anti-icing fluids and their effects on the physical properties of the solutions, especially viscosity, surface tension,freezing point and corrosive effect which enable the design of the de/anti icing fluid composition. A number of polymers and surfactants were dissolved in water-glycol solutions and used in different compositions to get the desired viscosity and surface properties. The dependence of viscosity on polymer concentration, pH of the solutions, glycol content, surfactant concentration, temperature and shear rate were investigated and reported in detail. Among various chemicals, slightly crosslinked and hydrophobically modified polyacrylic acid was utilized as a thickener, sodium oleate and tributyl amine were used as surface agents in the de/anti-icing solutions whose physical properties satisfied the desired requirements. In addition to the studies about de/anti icing solutions, synthesis of a new polymer namely poly (DADMAC-co-vinyl pyyrolidone) was made and its characterization and performance tests were performed. High swelling ratios (up to 360) were attained with 0.5 % crosslinker in 2-3 minutes. Moreover, swellings of the gels were demonstrated to be independent of pH. It was also thought that such a copolymer having anti-bacterial effect induced by DADMAC (Diallyldimethyl ammonium chloride) segments and biocompatability of NVP (N-vinyl pyyrolidone) component would be of interest in biorelated areas.