COMPATIBILITY STUDIES OF FLAME RETARDANTS IN PROPELLANTS

摘要

The influence of flame retardants on the chemical stability was studied on experimental samples of propellants containing various stabilizers and nitroglycerin contents. Heat flow, gas evolution and stabilizer depletion were evaluated as the measures of chemical stability. These measures were not changed by the presence of potassium bitartrate or sodium oxalate. Potassium sulphate decreases the stability slightly. Potassium nitrate decreases it in a high extent regardless of the stabilizer used. The increases of heat flows and gas evolution rates in the presence of potassium nitrate were more expressed in samples with higher nitroglycerin content and in those stabilized by 2-nitrodiphenylamine, triphenylamine or diphenylamine after its complete depletion. The smallest influence of potassium nitrate on the ageing behaviour was found in cases of akardite II stabilized samples. Based on HPLC analyses akardite II was involved in the reactions between potassium nitrate and nitrate esters of propellants very much, 2-NDPA was affected a little bit. No stabilizer interaction was detected with Cl and DPA. In order to explain the nature of the reaction of potassium nitrate an extended set of samples cured with other nitrates and chlorides was prepared. No increased heat flow was observed at all in 2-nitrodiphenylamine stabilized samples when samples were treated by barium nitrate, strontium nitrate, or chlorides. When lithium nitrate or sodium nitrate was incorporated the propellants show a higher activity compared to samples without flame retardant, but the effect is smaller than the one caused by potassium nitrate. These results lead us to suggestion that the cation may also play a role, whether it forms a complex with the nitrates which will lower their reactivity or whether the cations are coordinated in some way to the nitrate esters which will increase their capability to undergo decomposition reactions.