Study On Synthesis Of Polyurethane And Their Performance For Bonding Ammonium Nitrate

Ammonium nitrate is the key component of industrial explosive and solid propellant. However,it is easily hygroscopic and caking and the crystal will be transformed in the different situations,which affect its application on propellant and explosive.The key to decrease their hygroscopicity is improving the surface structure,reducing the surface energy and raising their hydrophobicity.A fine method is wrapping around the surface of ammonium nitrate by polymer,and forming a hydrophobe layer on the surface.This paper is focused on the synthesis of bonded ammonium nitrate,and improves its hydrophobicity,which also has higher antiknock capability.The experiment can be divided into two parts:firstly,the synthesis of polyurethane in chain and their bonded performance were characterized;secondly, the synthesis of polyfunctional isocyanate and their bonded characteristic in the system that cross-linked by small molecular is tested.Firstly,different polyurethanes were synthesized form MDI and N210,and cross-linked with amine and hydroxyl curative agent separately in order to form different bonded system. Every factor on their bonded properties was studied by orthogonal experiment,which obtained a optimized process.Secondly,the branched polyurethane was synthesized form MDI and N330,which is cross-linked by glycol in the different conditions.Also,the best synthesis process was obtained from orthogonal experiment.The experiment results show that:the content of isocyanate group in the polyurethanes is up to 1.834%under 80℃and the reaction time is 2h,which is closed to the theoretical yield 1.85%.The different proportion of polyol can improve the bonded body's mechanical properties.When the n_-N210:n_-N330=1:1 and the n_-NCO:n_-OH=1.3:1,its tensile strength is 23.6MPa,the radio of elongation at break is 317%,the hygroscopicity is reduced to 3.31%, and the strength of antiknock is up to 72cm.The best process to synthesis of polyurethane is that the usage of ammonium nitrate is 80%under 70℃,9kg pressure in 4h,which has the lowest hygroscopicity,4.30%.When the usage of ammonium nitrate is 75%under 65℃,9kg pressure in 6h,the largest strength of antiknock can be obtained,which is 43cm.