Pyrotechnic compositions using polyurethane as binder were designed to maximize the temperature of combustion and the burn rate. The flares consisted in mixtures of potassium perchlorate/Mg-Al alloy/polyurethane/additives. In order to determine the optimum input ratio that conducts to the most appropriate solution in terms of theoretical amount of heat released, specific volume of gaseous products and chemical composition, Explo5� thermochemical software runs were executed. Further, the temperature of combustion and the burn rate were determined by infrared thermography, while the heat of combustion and the specific volume of gases were obtained using an adiabatic calorimeter coupled with a Julius-Peters volumeter. The fuel ratio was varied in the compositions in order to optimize the combustion, and the addition of chlorinated rubber confirmed a significant enhancement in both parameters.
The present research focuses on the characterisation of a new formulation for thermal decoy pyrotechnic composition, as an alternative to magnesium-teflon-viton (MTV) formulations. The oxidant used in the composition is potassium perchlorate, given its good thermal stability and high percentage of available oxygen. The fuel of choice is magnalium (alloy of Al-Mg 50-50 % wt.), as an higher energy alternative to magnesium. The binder used in the composition is a blend of solvent free polyurethane and a chlorinated rubber. The main advantages of this composition are related to the high thermal stability, the ease of processing, by squeeze casting method and its good combustion performance (temperature and burn rate profile). The use of chlorinated rubber in the composition is beneficial, as a sensible increase in the burn rate and combustion temperature is observed. The morphological properties and chemical composition of the material is evidenced by SEM-EDS analysis while the burn rate and combustion temperature is recorded with a high speed thermal camera. The combustion heat and specific volume is calculated with a dedicated thermochemical code while the results are validated in experimental determinations. The presented formulation can represent a more safe and cost effective material to be used in thermal countermeasure ammunitions.
A series of methods were employed to assess the performances of advanced coating materials based on components that can modify the spectral parameters of the surfaces on which these materials are applied in order to obtain passive military camouflage. Powder materials with high infrared (IR) reflectance were used to obtain this type of coatings, which also ingrain in their structure a significant volume of air that allow limitation of the radiative heat transfer of the coated source. The components were embedded in a polyurethane matrix, which facilitated the coating process on different surfaces. The bicomponent polyurethane-based binder used within the different composition tested is transparent to incident IR radiation, has no organic solvents, is highly flexible and possesses remarkable physical, chemical and mechanical properties: high surface adhesion, high flexibility and resistance against a number of chemical agents and external factors with destructive effect. The efficiency of these composite materials was further demonstrated by analyzing the thermal images of different objects.
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